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  • Articles  (11,179)
  • Articles: DFG German National Licenses  (11,179)
  • Springer  (11,179)
  • 1990-1994  (11,179)
  • Geosciences  (10,022)
  • Nature of Science, Research, Systems of Higher Education, Museum Science  (1,157)
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  • Articles  (11,179)
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  • 1
    Electronic Resource
    Electronic Resource
    Operator and integro-differential representations of conditional and unconditional stochastic subsurface flow (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 157-172 
    Details
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Operator representations of stochastic subsurface flow equations allow writing their solutions implicitly or explicitly in terms of integro-differential expressions. Most of these representations involve Neumann series that must be truncated or otherwise approximated to become operational. It is often claimed that truncated Neumann series allow solving groundwater flow problems in the presence of arbitrarily large heterogeneities. Such claims have so far not been backed by convincing computational examples, and we present an analysis which suggests that they may not be justified on theoretical grounds. We describe an alternative operator representation due to Neuman and Orr (1993) which avoids the use of Neumann series yet accomplishes a similar purpose. It leads to a compact integro-differential form which provides considerable new insight into the nature of the solution. When written in terms of conditional moments, our new representation contains local and nonlocal effective parameters that depend on scale and information. As such, these parameters are not unique material properties but may change as more is learned about the flow system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589896
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  • 2
    Electronic Resource
    Electronic Resource
    Groundwater contaminant transport including adsorption and first order decay (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 185-205 
    Details
    ISSN: 1436-3259
    Keywords: Contaminant transport ; adsorption ; decay ; random walk ; killing ; Kolmogorov equations ; contamination of a well
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This study deals with the transport of a contaminant in groundwater. The contaminant is subject to first order decay or linear adsorption. Its displacement can be modeled by a random walk process in which particles are killed at exponentially distributed times. Dirichlet problems are derived for the rate and mean time at which contaminated particles reach a particular part of the boundary of a certain domain. These Dirichlet problems are solved asymptotically for two types of 2D-flow patterns: flow parallel to the boundary of a domain and arbitrary flow towards a well in an aquifer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01587234
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  • 3
    Electronic Resource
    Electronic Resource
    Nonequilibrium statistical mechanical derivation of a nonlocal Darcy's Law for unsaturated/saturated flow (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 109-116 
    Details
    ISSN: 1436-3259
    Keywords: Unsaturated ; nonlocal ; memory ; statistical physics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract As illustrated variously by wetting and drying scanning curves, flow in unsaturated porous media is inherently nonlocal. This nonlocality is also manifest in hysteresis in the classical Darcy conductivity. It is the authors' belief that most current theories of unsaturated/saturated flow are often inadequate, as they do not account for spatial nonlocality and memory. Here we provide a fundamental theory in which nonlocality of the flow constitutive theory is a natural consequence of force balances. The results are derived from general principles in statistical physics and under appropriate limiting conditions, the classical Darcy's Law is recovered for saturated flow. A notable departure in this theory from other nonlocal flow theories is that a classical Darcy type equation on a small scale need not exist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589892
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  • 4
    Electronic Resource
    Electronic Resource
    Solution of stochastic groundwater flow by infinite series, and convergence of the one-dimensional expansion (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 139-155 
    Details
    ISSN: 1436-3259
    Keywords: Porous media ; random media ; random fields ; groundwater flow ; stochastic hydrology ; stochastic partial differential equations ; perturbation methods ; Taylor expansions ; hierarchical systems ; Green's functions ; effective conductivity ; homogenization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper investigates analytical solutions of stochastic Darcy flow in randomly heterogeneous porous media. We focus on infinite series solutions of the steady-state equations in the case of continuous porous media whose saturated log-conductivity (lnK) is a gaussian random field. The standard deviation of lnK is denoted ‘σ’. The solution method is based on a Taylor series expansion in terms of parameter σ, around the value σ=0, of the hydraulic head (H) and gradient (J). The head solution H is expressed, for any spatial dimension, as an infinite hierarchy of Green's function integrals, and the hydraulic gradient J is given by a linear first-order recursion involving a stochastic integral operator. The convergence of the ‘σ-expansion’ solution is not guaranteed a priori. In one dimension, however, we prove convergence by solving explicitly the hierarchical sequence of equations to all orders. An ‘infinite-order stochastic solution is obtained in the form of a σ-power series that converges for any finite value of σ. It is pointed out that other expansion methods based on K rather than lnK yield divergent series. The infinite-order solution depends on the integration method and the boundary conditions imposed on individual order equations. The most flexible and general method is that based on Laplacian Green's functions and boundary integrals. Imposing zero head conditions for all orders greater than one yields meaningful far-field gradient conditions. The whole approach can serve as a basis for treatment of higher-dimensional problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589894
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  • 5
    Electronic Resource
    Electronic Resource
    A probability-weighted moment test to assess simple scaling (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 173-183 
    Details
    ISSN: 1436-3259
    Keywords: Probability weighted moment ; scaling in rainfall ; stable distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract We present a statistically robust approach based on probability weighted moments to assess the presence of simple scaling in geophysical processes. The proposed approach is different from current approaches which rely on estimation of high order moments. High order moments of simple scaling processes (distributions) may not have theoretically defined values and consequently, their empirical estimates are highly variable and do not converge with increasing sample size. They are, therefore, not an appropriate tool for inference. On the other hand we show that the probability weighted moments of such processes (distributions) do exist and, hence, their empirical estimates are more robust. These moments, therefore, provide an appropriate tool for inferring the presence of scaling. We illustrate this using simulated Levystable processes and then draw inference on the nature of scaling in fluctuations of a spatial rainfall process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01587233
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  • 6
    Electronic Resource
    Electronic Resource
    Announcements (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 156-156 
    Details
    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589895
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  • 7
    Electronic Resource
    Electronic Resource
    Probabilistic assessment of travel times in groundwater modeling (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 19-55 
    Details
    ISSN: 1436-3259
    Keywords: Indicator kriging ; stochastic simulation ; soft data ; Walker Lake ; sequential simulation ; scaling-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A Monte Carlo approach is described for the quantification of uncertainty on travel time estimates. A real (non synthetic) and exhaustive data set of natural genesis is used for reference. Using an approach based on binary indicators, constraint interval data are easily accommodated in the modeling process. It is shown how the incorporation of imprecise data can reduce drastically the uncertainty in the estimates. It is also shown that unrealistic results are obtained when a deterministic modeling is carried out using a kriging estimate of the transmissivity field. Problems related with using sequential indicator simulation for the generation of fields incorporating constraint interval data are discussed. The final results consists of 95% probability intervals of arrival times at selected control planes reflecting the original uncertainty on the transmissivity maps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581389
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  • 8
    Electronic Resource
    Electronic Resource
    Joint conditional simulations and the spectral approach for flow modeling (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 79-108 
    Details
    ISSN: 1436-3259
    Keywords: Stochastic flow equations ; conditional simulation ; spectral representations ; joint conditioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The use of data to condition single random fields has a well-established history. However, the joint use of data from several cross-correlated random fields is not as well developed. For example, the use of both transmissivity and head data in a steady state 2-d stochastic flow problem is essentially an inverse problem that is very important for both flow and transport predictions. This problem is addressed here by using a combination of numerical simulation and analytical methods and its application illustrated. The type of information conveyed by the different data categories is explored. The results presented are especially interesting in that head and transmissivity each give different information: Head values would appear to constrain the geometry of the paths while transmissivity data yields information about travel times. The linearized model is expanded to an iterative procedure and the “true” conditional distribution at several locations is compared with the iterative solution. The problem mentioned above is one with a special transfer function specified by the flow equation. In the second part of the paper a Fast Fourier Transform method for generation and conditioning of two or more random fields is introduced. This procedure is simple to implement, fast and very flexible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581391
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  • 9
    Electronic Resource
    Electronic Resource
    Effective hydraulic conductivity of nonstationary aquifers (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 1-17 
    Details
    ISSN: 1436-3259
    Keywords: Stochastic diffusion equations ; effective hydraulic conductivity ; correlation scale ; heterogeneous aquifers ; spectral representation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Assuming that the ln hydraulic conductivity in an aquifer is mathematically approximated by a spatial deterministic “surface”, or trend, plus a stationary random noise, we treat the problem of finding what the effective hydraulic conductivity of that aquifer is. This problem is tackled by spectral methods applied to a type of diffusion equation of groundwater flow, together with suitable coordinate transformations. Analytical (exact) solutions in terms of elementary functions are presented for one- and three-dimensional finite and infinite domains. Stability criteria are obtained for the solutions, in terms of a critical parameter, that turns out to involve the product of correlation scale and trend gradient. For the case of finite and symmetrical domains, additional provisions to insure the stability of numerical calculations of effective hydraulic conductivity are provided. Effective hydraulic conductivity is an important property, with potential applications in the calibrations of groundwater and transport numerical models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581388
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  • 10
    Electronic Resource
    Electronic Resource
    MMO: An improved estimator for log-Pearson type-3 distribution (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 219-231 
    Details
    ISSN: 1436-3259
    Keywords: Parameter estimation ; flood frequency analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A mixed method combining the method of moments and the method of optimization (MMO) was developed for estimating the parameters of the log-Pearson type 3 (LP3) distribution. The MMO estimates the parameters of mean and standard deviation by the method of indirect moments (MIM) and estimates the coefficient of skewness by minimizing both the relative root average square error (RRASE) and the relative average bias (RAB). Both the predictive capability and descriptive capability of six popular estimation methods were evaluated using 90 sets of observed flood data and six selected LP3 populations with 1000 samples for each selected sample size. The performance of the MMO was compared with those of five other selected estimation methods. A weighted ranking index (WRI) procedure was developed to help select the best combination of distribution and method for the Louisiana flood data. The WRI takes both the predictive capability and the descriptive capability into account in the evaluation. The combination of LP3/MMO was found to be the best combination for Louisiana flood data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01587236
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  • 11
    Electronic Resource
    Electronic Resource
    Unsaturated flows in soils with self-similar hydraulic conductivity distribution (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 281-300 
    Details
    ISSN: 1436-3259
    Keywords: Stochastic analysis ; unsaturated flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract In this article, we are concerned with the statistics of steady unsaturated flow in soils with a fractal hydraulic conductivity distribution. It is assumed that the spatial distribution of log hydraulic conductivity can be described as an isotropic stochastic fractal process. The impact of the fractal dimension of this process, the soil pore-size distribution parameter, and the characteristic length scale on the variances of tension head and the effective conductivity is investigated. Results are obtained for one-dimensional and three-dimensional flows. Our results indicate that the tension head variance is scale-dependent for fractal distribution of hydraulic conductivity. Both tension head variance and effective hydraulic conductivity depend strongly on the fractal dimension. The soil pore-size distribution parameter is important in reducing the variability of the unsaturated hydraulic conductivity and of the fluxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01588758
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  • 12
    Electronic Resource
    Electronic Resource
    Entropy principles in the prediction of water quality values at discontinued monitoring stations (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 301-317 
    Details
    ISSN: 1436-3259
    Keywords: Change ; discontinued stations ; entropy ; networks ; optimization ; prediction ; unbiased ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A new methodology for predicting water quality values at discontinued water quality monitoring stations is proposed. The method is based upon the Principle of Maximum Entropy (POME) and provides unbiased predictions of water quality levels at upstream tributaries and on the mainstem of a river given observed changes in the distribution of the same water quality parameter at a downstream location. Changes in the values of water quality parameters which are known a priori to have occurred upstream, but which are not sufficiently large to account for all the observed change in the same water quality parameter at the downstream location are able to be incorporated in the method through the introduction of a new term in the basic entropy expression. Application of the procedure to water quality monitoring on the Mackenzie River in Queensland, Australia indicates the method has considerable potential for prediction of water quality at discontinued stations. The method also has potential for identifying the location of causes of observed changes in water quality at a downstream station.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01588759
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  • 13
    Electronic Resource
    Electronic Resource
    Sampling variance of a T-year flood estimated by curve-fitting (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 233-258 
    Details
    ISSN: 1436-3259
    Keywords: Flood ; China ; river ; sampling variance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The sampling variance of a T-year flood when estimated using a curve-fitting method results from the errors in hydrologic observations, plotting positions, and model-fitting. This paper develops a method to quantify the contribution of plotting positions to the sampling variance of the T-year flood magnitude. Application of the method to 150 flood-flow data sets of 41 rivers in the People's Republic of China show that the errors due to plotting positions contribute more to the sampling variance than others.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01587237
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  • 14
    Electronic Resource
    Electronic Resource
    Determination of unit hydrographs by multiple storm analysis (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 269-280 
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    ISSN: 1436-3259
    Keywords: Unit hydrograph ; least square methods ; regression analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper discusses the derivation of a unit hydrograph by multiple storm analysis using least squares methods. Variations of least squares method was generalized using the framework of weighted ridge analysis. The paper also shows two theorems to support using multi-storm analysis to derive UH. In addition, an issue was addressed on the scaling effect in the conventional multi-storm analysis which could create potential bias toward large storms in deriving a multi-storm UH. For that, a simple scaling procedure was proposed to reduce such potential bias problem. Numerical investigations were conducted to examine the performance of the scaling procedure by comparing with the conventional multi-storm analysis (without scaling) and the HEC-1 weighing procedures. Based on various performance criteria using a total of 39 storms from three watersheds, the proposed scaling procedure was found to produce a quite desirable UH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01588757
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  • 15
    Electronic Resource
    Electronic Resource
    Modeling of transport in groundwater for environmental risk assessment (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 57-77 
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    ISSN: 1436-3259
    Keywords: Stochastic transport ; risk assessment ; concentration CDF ; exceedance probabilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper presents the principles underlying a recently developed numerical technique for modeling transport in heterogeneous porous media. The method is then applied to derive the concentration mean and variance, the concentration CDF, exceedance probabilities and exposure time CDF, which are required by various regulatory agencies for risk and performance assessment calculations. The dependence of the various statistics on elapsed travel time, location in space, the dimension of the detection volume, natural variability and pore-scale dispersion is investigated and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581390
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  • 16
    Electronic Resource
    Electronic Resource
    Stochastic space transforms in subsurface hydrology — Part 2: Generalized spectral decompositions and plancherel representations (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 117-138 
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    ISSN: 1436-3259
    Keywords: Stochastic hydrology ; random fields ; space transformations ; generalized functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract In earlier publications, certain applications of space transformation operators in subsurface hydrology were considered. These operators reduce the original multi-dimensional problem to the one-dimensional space, and can be used to study stochastic partial differential equations governing groundwater flow and solute transport processes. In the present work we discuss developments in the theoretical formulation of flow models with space-dependent coefficients in terms of space transformations. The formulation is based on stochastic Radon operator representations of generalized functions. A generalized spectral decomposition of the flow parameters is introduced, which leads to analytically tractable expressions of the space transformed flow equation. A Plancherel representation of the space transformation product of the head potential and the log-conductivity is also obtained. A test problem is first considered in detail and the solutions obtained by means of the proposed approach are compared with the exact solutions obtained by standard partial differential equation methods. Then, solutions of three-dimensional groundwater flow are derived starting from solutions of a one-dimensional model along various directions in space. A step-by-step numerical formulation of the approach to the flow problem is also discussed, which is useful for practical applications. Finally, the space transformation solutions are compared with local solutions obtained by means of series expansions of the log-conductivity gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589893
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  • 17
    Electronic Resource
    Electronic Resource
    Comparative evaluation of Poisson partial duration models for mixed flood populations (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 207-218 
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    ISSN: 1436-3259
    Keywords: Partial duration ; Weibull ; nonhomogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Simple homogeneous formulations of two extreme value partial duration flood models are compared to more sophisticated compound formulations in terms of asymptotic performance of quantile estimates. The compound model formulations were developed to model flood series resulting from mixed climatological processes. It was found that only in the case of marked nonhomogeneity in the data samples did the compound formulation of the models offer significant advantages in terms of variance of quantile estimates. However, the estimates from the homogeneous model were significantly biased in the negative direction. This negative bias of quantile estimates from the simple model was even more pronounced when the more sophisticated Weibull model was used as the base.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01587235
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  • 18
    Electronic Resource
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    A stochastic integral equation analog of rainfall-runoff processes for evaluating modeling uncertainty (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 259-268 
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    ISSN: 1436-3259
    Keywords: Rainfall ; runoff ; modeling ; uncertainty ; stochastics ; stochastic integral equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract In this paper a very general rainfall-runoff model structure (described below) is shown to reduce to a unit hydrograph model structure. For the general model, a multi-linear unit hydrograph approach is used to develop subarea runoff, and is coupled to a multi-linear channel flow routing method to develop a link-node rainfall-runoff model network. The spatial and temporal rainfall distribution over the catchment is probabilistically related to a known rainfall data source located in the catchment in order to account for the stochastic nature of rainfall with respect to the rain gauge measured data. The resulting link node model structure is a series of stochastic integral equations, one equation for each subarea. A cumulative stochastic integral equation is developed as a sum of the above series, and includes the complete spatial and temporal variabilities of the rainfall over the catchment. The resulting stochastic integral equation is seen to be an extension of the well-known single area unit hydrograph method, except that the model output of a runoff hydrograph is a distribution of outcomes (or realizations) when applied to problems involving prediction of storm runoff; that is, the model output is a set of probable runoff hydrographs, each outcome being the results of calibration to a known storm event.
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    URL: http://dx.doi.org/10.1007/BF01588756
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  • 19
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    Erratum (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 318-318 
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    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01588760
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  • 20
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    Studies of the structure and stability of base pair mismatches, base pairs involving modified bases, and DNA-drug complexes (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 5-15 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665340
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  • 21
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    Toward the rational design of materials (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 21-26 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The emphasis of computational chemistry has traditionally been slanted toward the study of isolated organic systems, and in particular toward methods of drug design. The requirements for the study of materials are different, we are often concerned with metal containing species and properties that arise from interactions between unit molecules in the solid state. We have developedcrystal, a molecular modeling environment that provides both the capability to perform calculations on metal complexes, and an array of visualization tools to aid in the design of solid-state systems.
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    URL: http://dx.doi.org/10.1007/BF01665342
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  • 22
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    Symmetry old and new: Some recent examples of the role of symmetry in X-ray analysis (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 51-60 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Two recent examples in X-ray structure analysis at opposite ends of the molecular weight range, in which very careful consideration of space group and diffraction symmetry was necessary to resolve all the associated problems, are described. Case 1 involves the structures of (1) transdiBromo (1,4,8,11-tetraazacyclotetradecane) chromium (III) bromide and (2) the corresponding trans-bromo-chloro compound. Both crystallise in space groupP42/m with unit cell dimensions sufficiently close to suggest that the structures are isomorphous. It is shown however that the structures are not superimposable or even related by simple rotation or inversion, but that it is necessary to apply a hypothetical glide operation in order to bring the structures into coincidence. The organic moieties are thus structural enantiomorphs in spite of existing in a centrosymmetric space group. Case 2 involves studies on a co-crystallised derivative of the enzyme RNase with deoxycytidylyl-3′–5′-deoxyguanosine (dCpdG). Preliminary X-ray precession photographs, from low quality crystals, indicated an orthogonal C-centred unit cell, but were unable to define the true diffraction symmetry, which wasnot orthorhombic. The true symmetry was discovered only after solving the structure in a second (erroneous) cell and careful inspection of the lattice and diffraction symmetry from the measured intensity values.
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    URL: http://dx.doi.org/10.1007/BF01665345
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  • 23
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    Crystal structure of 2,2′-diformyl 4,4′-dimethyl 6,6′-[piperazine-1,4-diyl bis-(methylene)]bis phenol (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 71-74 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compund C22H26N2O4,Mr=382.46 crystallizes in the orthorhombic space group P212121 with α=8.867(1)Å,b=13.228(2)Å,c=17.029(3)Å,V=1956.7(2)Å3,Z=4, Dcal=1.30 Mgm−3,F(000)=816, μ=6.89 cm−1, λ(CuKα)=1.5418 Å andT=298 K. The structure was solved by direct methods and refined by full-matrix least-squares. The finalR=0.046 for 1995 unique reflections. The phenyl rings are coplanar (oriented at an angle of 6.4(1)o) and orients at an angle of 112.2(1)o and 115.7(1)o, respectively with the piperazine ring. The piperazine ring adopts achair conformation and the substituents at the N-atoms are in an equatiorial position.
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    Synthesis and structural characterization of 2,6-bis-(N-methylenemorpholino)-4-methylphenol (MMP) and 2,6-bis-(N-methylenemorpholino)-4-bromophenol (MBrP) (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 83-87 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract MMP: C17H26N2O3,M r =306.40, monoclinic, space groupP21/c,a=10.927(2),b=10.777(2),c=14.197(2) Å, β=94.04(2)°,V=1667.7(5) Å3,D cal=1.22 Mgm−3,Z=4,F(000)=664, μ=5.93 cm−1,T=293K. FinalR=0.049 andwR=0.063 for 2724 observed reflections. MBrP; C16H23N2O3Br,M r =371.27, monoclinic, space groupP21/c,a=10.955(1),b=10.785(1),c=14.213(1) Å, β=94.54(2)°,V=1674.0(4) Å3,D cal=1.48 Mgm−3,Z=4,F(000)=768, μ=32.35 cm−1,T=293K. FinalR=0.055 andwR=0.069 for 2886 observed reflections. MMP and MBrP are isostructural and in both the molecules the morpholino rings assume a chair conformation.
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    Polymorphism of N-(2,6-dioxo-3-piperidyl)pthalimide (thalidomide): Structural characterization of a second monoclinic racemic modification (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 95-99 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of the drug N-(2,6-dioxo-3-piperidyl)pthalimide (thalidomide), C13H10N2O4, obtained from 1∶1 dimethyformamide-ethanol solution, is reported. This species is monoclinic, space groupC2/c, witha=20.679(5),b=8.042(2),c=14.162(5) Å, β=102.86(3)°,Z=8,R=0.051 for 1674 unique reflections. crystal packing is determined by intermolecular N−H... O hydrogen bonding which is more extensive than that reported in the literature for a racemate of thalidomide crystallizing in space groupP21/n. Comparison of the melting behavior and X-ray powder diffractograms of the two racemic polymorphs shows that they are distinctly different, allowing easy identification of these species. By comparing experimental X-ray powder patterns with those calculated from single crystal data, it was concluded that neither of these polymorphs undergoes a phase change on trituration.
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    Spectroscopic, thermal, and X-ray diffraction studies of tetrakis(thiourea) palladium chloride bis (5,7-dimethyl[1,2,4]triazolo[1,5-a]pyrimidine dihydrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 669-673 
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    ISSN: 1572-8854
    Keywords: X-Ray diffraction studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the title compound, ·[Pd(S=C(NH2)2)4]Cl2·2dmtp·2H2O. has been determined and refined to a finalR=0.034. The cation is centrosymmetric with the Pd atom existing in a square planar geometry with two disparate Pd−S bond distances of 2.3129(9) and 2.292(1)Å. Interatomic parameters are reported for the first non-coordinated dmtp molecule; these suggest the predominance of a particular canonical form in the solid state. The lattice is stabilized via a series H-bonding contacts involving the thiourea. Cl− and dmtp species. Crystals of [Pd(S=C(NH2)2)4]Cl2 · 2dmtp · 2H2O are monoclinic with space groupP21/c, and unit cell dimensionsa=15.129(1),b=8.512(1),c=12.663(1) Å, β=104.05(1)°.
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    Crystal structures of 2-pyrazinecarboxylato silver(I) and ammine 2,3-pyrazinecarboxylato disilver(I) (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 681-684 
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    ISSN: 1572-8854
    Keywords: Silver(I) ; anionic forms ; 2-pyrazinecarboxylic and 2,3-pyrazinedicarboxylic acids
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract X-ray analysis has shown that the complexes of silver(I) with the anionic forms of 2-pyrazinecarboxylic and 2,3-pyrazinedicarboxylic acids are three-dimensional network polymers. Ag(C5H3O2N2) (1) crystallizes in space groupPna21 witha=7.028(2),b=11.510(3),c=6.949(2) Å andZ=4. Silver tetrahedral coordination occurs through three ligands: the first one acts as a bidentate chelator (Ag−O=2.539(4), Ag−N=2.334(4)Å), the second one involves one N pyrazine atom (Ag−N=2.196(4)Å) and the third one bonds through one O-carboxylato atom (Ag−O=2.323(4)Å). The dinuclear complex Ag2(C6H2O4N2)(NH3) (2) crystallizes in space groupP21/c witha=7.775(2),b=16.455(2),c=7.174(1) Å, β-115.21(1)° andZ =4. Each of the two silver atoms shows a trigonal environment. The first silver atom involves two O carboxylic atoms (Ag−O=2.312(4), 2.374(4)Å) and one N pyrazine atom (Ag−N=2.277(3)Å) belonging to three different ligands. The second one involves one O carboxylic atom (Ag−O=2.364(3)Å) and one N pyrazine atom (Ag−N=2.304(4)Å) from the same chelating ligand and one N ammine atom (Ag−N=2.158(5)Å).
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    Future contributions to Journal of Chemical Crystallography (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 101-101 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
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    Crystal structure, spectroscopic study, molecular modeling, andin vitro antimicrobial activity testing of 2,2′-thiobis[4,6-diphenylpyridine-3-carbonitrile] (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 675-679 
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    ISSN: 1572-8854
    Keywords: Molecular and crystal structures ; antimicrobial activity testing
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The molecular and crystal structures of the title compound have been determined. The crystals are monoclinic:P21/n (14),a=11.072(2),b=14.556(2),c=17.569(3)Å, β=97.85(1)°.V c=2805Å3,Z=4,D x=1.285 Mg m−3, MoKα(λ=0.71069 Å). The molecule adopts a twisted conformation in which the relative orientations of the pyridine nitrogen atoms N101 and N201 with respect to the C−S−C angle are N101-inside. The AM1 and PM3 semiempirical calculations performed agree with the crystal structure. Mass and spectral data (ir. uv,1H and13C nmr) are also reported. Thein vitro tests indicate absence of antimicrobial activity.
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    Very strong hydrogen bonds in hydrated 1:1 adducts of an olefinic double betaine with perchloric and nitric acids: L·HClO4·H2O and L·HNO3·H2O [L=cis-(p-Me2N+C5H4N)2C2(COO−)2] (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 689-694 
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    ISSN: 1572-8854
    Keywords: Hydrated adducts ; olefinic double betaine ; very strong hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The hydrated 1:1 adducts of an olefinic double betaine with perchloric and nitric acids, L·HClO4·H2O I and L·HNO3·N2O2 [L=cis-(p-Me2N+C5H4N)2C2(COO−)2], have been shown to be nearly isostructural by X-ray crystallography and infrared spectroscopy. The common cationic unit HL+ of both compounds exhibits significant semi-quinonoid character and possesses symmetrym, ist two coplanar carboxylate groups being linked by a very strong, nearly linear intramolecular O−H−O hydrogen bond [O...O 2.397(9)Å and O−H−O 167.1° for1; 2.388(7)Å and 167.4° for2]. The HL+ units are further connected by intermolecular O−H...O hydrogen bonds between the exocyclic carboxyl oxygen atoms and the water molecules to generate polymeric zigzag chains running parallel to thec axis, and the disordered ClO4 or NO 3 − anions occupy channels running parallel to thea axis in the resulting host lattice.
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    Crystal structure of Pt(S2COEt)2 (1994)
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    Journal of chemical crystallography 24 (1994), S. 707-710 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; platinum ; xanthate ; square planar
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The crystals of Pt(S2COEt)2 are orthorhombic, Pbca, with (at 20°C)a=7.799(3),b=7.368(6),c=20.588(7) Å.D cale=2.46g cm−3 forZ=4. The platinum atom resides on a crystallographic center of inversion and is bound to the four sulfur atoms of the xanthato ligand in a square planar geometry. The Pt−S distances are 2.313(6) and 2.320(7)Å with an intraligand S−Pt−S angle of 75.1(2)°.
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    X-ray crystal structure of 1,4-diphenylbutadiyne (1994)
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    Journal of chemical crystallography 24 (1994), S. 715-717 
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    Keywords: cuprate ; diyne ; herringbone
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Crystals of 1,4-Diphenylbutadiyne,1, have been isolated from the decomposition of the cuprate prepared from the reaction between lithium phenylacetylide and copper(I)cyanide in diethylether solution at room temperature. 1,4-Diphenylbutadiyne,I, organizes itself into the expectedherringbone motif in the solid state.
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    Structures of 1,2,3,4-tetrahydro-6H-pyrimido[2,1-b]-quinazolin-6-one and its hydrochloride (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 725-729 
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    Keywords: Pyrimido [2,1-b]quinazoline ; hydrochloride ; neuroleptic
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract C11H11N3O, m.p. 243°C, P2/n,Z=4,a=5.843(2),b=14.241(3),c=11.102(1) Å, β=93.30(2)°,R=0.046; C11H11N3O·HCl·H2O, Pca21,Z=8,a=18.640(2),b=8.894(2),c=14.404(2)Å,R=0.062. The molecules of the free base are in 1H-tautomeric form. N(1)-H...N(11) hydrogen bonds join molecules of the free base into dimers, which enable tautomeric rearrangement (not observed in this study) also in the solid state without any changes in molecular packing. The quinazoline system deviates slightly from planarity and benzene π electrons are partially localized at C(7)−C(8) and C(9)−C(10) bonds as seen from their lengths of about 1.375 Å, while other bonds in the benzene ring are at least 0.02 Å longer.
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    Structure of methylphenylhydrazone form of 2-(2-methylphenylazo)-1,3-indandione (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 743-746 
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    ISSN: 1572-8854
    Keywords: Methylphenylhydrazone ; ketohydrazone ; tautomeric form
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The molecule crystallizes in a ketohydrazone tautomeric form. The tautomeric form is stabilized by a strong intramolecular hydrogen bond of 2.709(2) Å binding the 3-oxo to the nearest nitrogen atom in the azine chain. The compound crystallizes in the monoclinic space group P2l/c witha=7.0470(4),b=11.3090(9),c=16.2250(4) Å, β=90.310(3)°, V=1293.0(1) Å3, Z=4,Dx=1.3576 g cm−3 and μ(Cu-Kα)=7.03 cm−1. The molecule is nearly planar not regarding the methyl group; the small deviations from planarity are indicative of intramolecular interactions between the phenylazo group and indandione group. Some of the bond lengths and angles found in the molecule are distorted due to resonance, π-electron delocalization and strain. The relation between these chemical effects and structural results are discussed.
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    The crystal and molecular structure of N-(methylsulfonyl)-N-(2,6)-(dimethylphenyl)methanesulfonamide (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 759-762 
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    ISSN: 1572-8854
    Keywords: Sulfonamide ; methanesulfonanilide ; crystal structure ; molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound, crystallizes in the triclinic space group $$P\bar 1$$ witha=8.232(4),b=9.159(2),c=10.230(3)Å. α=74.07(3)°, β=72.50(4)°, γ=63.65(3)° andZ=2. The structure was solved by direct methods and refined by full matrix least squares methods toR=0.054 for 1817 observed reflections. The plane containing the nitrogen and sulfur atoms is perpendicular to the aromatic plane. One of the S−O bonds in each methanesulfonyl group is in nearly eclipsed conformation with the N−C bond.
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    Cholic acid inclusion compounds with ketone guests (1994)
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    Journal of chemical crystallography 24 (1994), S. 783-791 
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    Keywords: Cholic Acid ; Inclusion Compounds ; Ketone Guests
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Cholic acid forms inclusion compounds with acetone, methyl ethyl ketone and diethyl ketone. Crystal structures with these closely related guest molecules indicate variations in packing which result in respectively: unusual 2∶3 host: guest stoichiometry and loss of the 21 screw axis, doubling of the c axis with formation of two different channels and the usualP21 structure with 1∶1 host: guest stoichiometry.
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    The synthesis and crystal structure of [La(OH2)5(phen)2]Cl3·4H2O·phen (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 797-800 
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    ISSN: 1572-8854
    Keywords: La(III) ion ; phen ; Lanthanides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [La(OH2)5(phen)2]Cl3·4H2O·phen is centric, Pnna, witha=19.946(7),b=16.458(5),c=12.207(4)Å andD calc=1.57 g cm−3 forZ=4. The La(III) ion resides on a crystallographic twofold axis and is coordinated to four nitrogen atoms (from two phen molecules) and five water molecules resulting in a distorted tricapped trigonal prismatic geometry. An uncoordinated phen molecule, two chloride anions, and four uncoordinated water molecules are hydrogen bonded to the coordinated water molecules. The coordinated and uncoordinated phen molecules π-stack diagonally through the unit cell.
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    Future contributions to Journal of Chemical Crystallography (1994)
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    Journal of chemical crystallography 24 (1994), S. 817-817 
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    Source: Springer Online Journal Archives 1860-2000
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    The disordered macrocyclic, (15-ane N5) Cu(II)(ClO4)2 at low temperature (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 815-816 
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    Structure of sodium bis(pentadecatungstodiphosphato)diaquatetrazincate hydrate (16∶1∶50) (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 123-128 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Crystals of Na16[Zn4(H2O)2(α-P2W15O56)2]·∼50H2O are triclinic, $$P\bar 1$$ , witha+14.670(5),b+14.661(5),c+19.817(3)Å, α=84.95(3), β=81.51(3), γ=65.73(3)o. Least-squares refinement converged atR+0.053 for 5906 independent data withl〉3σ(I). The centrosymmetric anion consists of two α-P2W15O 56 12− ligands attached to a planar group of four Zn2+, two of which also carry water molecules. The distortions in the ZnO6 octahedra and in the W15 framework of the ligands are smaller than the corresponding distortions in the otherwise similar [Cu4(H2O)2(P2W15O56)2]16− anion.
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    Crystal and molecular structure of di-μ-chlorobis [N-(2-hydroxyethyl)salicylideneiminato-N,0,0′ copper(II)] hemihydrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 133-137 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The structure of the title compound. [Cu2Cl2(C9H10NO2)2]·1/2H2O. has been determined from single crystal X-ray diffraction data. The structure was solved by direct methods. Full-matrix leastsquares refinement of structural parameters led to a conventionalR factor of 0.056 for 3689 intensities above 3σ(l). There are two independent molecules [A andB] of the title compound in the asymmetric unit. These molecules are linked to one water molecule by a system of four hydrogen bonds. The comlexes contain pairs of deformed square-pyramidal copper(II) centers. A tridetate ligand L forms two condensed chelate rings with mean Cu−O(C−O)+1.900(6), mean Cu−O(C−OH)+2.004(6) and mean Cu−N-1.930(6)Å. A chloride ions complete the tetrahedral distorted basal plane of each Cu(II) ion forming a square pyramid with the longer fifth apical Cu−Cl bridging bond. The Cu...Cu nonbonding distances in the complexes are 3.445(1)Å for moleculeA and 3.494(1)Å for moleculeB.
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    The crystal and molecular structures of 2-hydroxy-1-naphthalenecarboxaldehyde and 3-hydroxy-2-naphthalenecarboxaldehyde (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 151-154 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The crystal and molecular structures of 2-Hydroxy-1-naphthalenecarboxaldehyde (I) and 3-Hydroxy-2-naphthalenecarboxaldehyde (II) were determined. Compound (I) crystallizes in the space groupP2 1/n witha+5.589(2),b+9.352(2), andc+15.490(3) Å, β=98.14(3)°, andZ+4. Compound (II) crystallizes inP2 1/n witha+16.831(11),b+5.936(3), andc+8.295(3) Å β=97.24(5)°. andZ+4. The structures were solved by direct methods, and refined by fullmatrix least squares toR+0.071 andR w+0.083 forI, andR+0.047 andR w+0.061 forII.
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    Crystal and molecular structure of (E)-2-t-butyl-3(3′-t-butyldimethylsiloxy)propyl-2-cyanocyclobutanone (1994)
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    Journal of chemical crystallography 24 (1994), S. 171-174 
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    Notes: Abstract The title compound crystallizes in the monoclinic space group P21/a, witha+12.906(9).b+11.604(2).c+14.631(9) Å, β=108.70(3)° andZ+4. The structure was solved by direct methods from diffractometer data and refined to a finalR value of 0.057 for 2020 independent reflections. The structure analysis confirms the cis disposition of the bulky substituents and indicates a puckered four-membered ring with a dihedral angle of 18.5° as expected for a non-centrosymmetrically substituted cyclobutanone.
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    Solid state structure of oxalato-(bis(dicyclohexylphosphino)-ethane) platinum(II)-acetonitrile solvate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 193-195 
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    Notes: Abstract C30H51NO4P2Pt-[C2H3N], orthorhombic,Pbca, a=16.132(1),b=16.610(2),c=24.001(2) Å.Z=8,D c=1.54 g cm−3,R=0.042,R w=0.048, GOF=1.33. The platinaoxalate (PtC2O2) ring fragment is essentially planar with Pt−O bond lengths of 2.067(8) and 2.058(7) Å.
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    Polymeric and mixed carboxylate compounds: Crystal structures of [Zn(tiglate)2]x and [Zn2(tiglate)3(crotonate)]x (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 211-217 
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    Notes: Abstract The crystal structures of [Zn(O2CC(CH3)CHCH3)2]x and [Zn2(O2CC(CH3)CHCH3)3-(O2CCHCHCH3)]x have been determined by single crystal X-ray diffraction. Both structures consist of chain polymers, in which pairs of zinc atoms are bridged alternately by three syn-syn carboxylates and by one syn-anti carboxylate. In the mixed carboxylate structure, the crotonate takes up preferentially the syn-anti bridge position. Vibrational and elemental analysis data indicate that the spontaneous solid-state reaction of zinc tiglate in air, accelerated for the tiglate and observable also for the mixed carboxylate compound by γ-ray or X-ray irradiation, gives an oxocentered tetranuclear complex [Zn4O(O2CR)6] rather than a polymerization through cross-linking of the unsaturated carboxylates.
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    The crystal and molecular structure of chandonium dibromide: A synthetic bisquaternary aza steroidal neuromuscular blocking agent (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 225-230 
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    Notes: Abstract The crystal and molecular structure of 17a-methyl-3-pyrrolidino-17a-aza-D-homo-5-androstene dimethyl bromide (HS818, chandonium dibromide). C26H46N2Br2, has been determined crystallographically by the heavy atom method and refined by full-matrix least-squares calculations toR =0.074 for 5045 reflections. The compound crystallizes in space groupP212121 witha=6.468(2),b=14.055(5),c=28.216(11) Å. The N+...N+ inter-onium distance in chandonium bromide is 10.32 Å, close to the distance of 10.29 Å observed in chandonium iodide. Rings A, C, and D have a chair conformation and ring B is in a half-chair conformation. Ring E has a distorted envelope conformation. All rings in the steroid skeleton aretrans-connected.
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    Synthesis and X-ray structure of [H3O+·18-crown-6] [Br−Br−Br−]; a compound containing both H3O+ and a linear and symmetrical Br 3 t- ion crystallized from aromatic solution (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 243-245 
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    Notes: Abstract [H3O+·18-crown-6][Br−Br−Br−] crystallizes in the triclinic space group P 1 witha=6.105(1),b=8.658(1),c=11.072(1)Å, α=71.35(1), β=77.58(1), γ=71.09(1)0, andD c=1.68 g cm−3 forZ=1. Refinement based on 1112 observed reflections led toR=0.044. The cation exhibits a planar oxonium ion bonded symmetrically to the 18-crown-6 (O(oxonium) resides 0.092 Å out of the plane of the crown ether oxygen atoms). The anion also resides on a center of inversion with Br−Br=2.530(1)Å.
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    2,8,10,11-tetrachloro-12-oxahexacyclo-[7.2.1.02,8.03,7.04,11.06,10]dodeca-1,9-diol and disorder and mixed crystals in a system of tetracyclo-[6.3.0.04,11.05,9]undecanone and undecanol derivatives (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 259-266 
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    Notes: Abstract 2,8,10,11-Tetrachloro-12-oxahexacyclo[7,2.1.02.8.03.7.04.11.06.10]dodeca-1,9-diol is a strained cage molecule containing six five-membered rings and a four-membered ring. Twenty-five of the internal angles are less than 105° with 6 ranging from 89.5(3) to 97.4(3)°. The base promoted reaction of 3,6-dipyridyl-1,2,4,5-tetrazine with tetracyclo[6.3.0.04.11.05.9]undecane-3,6-dione yields the monoketone 6,7-[3′,6′-di(2″-pyridyl)-4′,5′-pyridizino]tetracyclo[6.3.0.04.11.05.9]-undecan-2-one. This compound crystallizes in the centrosymmetric space group P21/n with enantiomers related by a center of symmetry. In the crystal investigated the molecules are disordered with each site containing about 80% of one isomer and 20% of the enantiomer. When the ketone is hydrogenated and the product isolated, two different crystals were found to have a ratio of alcohol to ketone of .71/.29 and .75/.25 or about 3/1. The alcohol and ketone occupy the same sites, but with opposite stereochemistries.
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    Structure ofcatena-(2-amino-1,3,4-thiadiazolium, 2-amino-1,3,4-thiadiazole bis(μ-iodo)-di-iodo-bismuth(III) (1994)
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    Journal of chemical crystallography 24 (1994), S. 277-280 
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    Notes: Abstract [(C2H4N3S) (C2H3N3S) BiI4]∞; [(HL) (L) BiI4]∞ (L=2-amino-1,3,4-thiadiazole),M r=919.86. monoclinic, P 1 21/a 1,a=7.622(1),b=18.977(2),c=12.821(1) Å, β=102.77(1)°, finalR=0.033. The crystals consist of HL+ cations, neutral L molecules and polymeric [BiI4] ∞ − anions built up of edge-sharing [BiI6]3− octahedra, with Bi−I(bridging) distances in the range 3.320(1)−3.057(1) Å and Bi−I(terminal) distances in the range 2.917(1)−2.929(1) Å. The1H and13C spectra in DMSO-d6 solution are used in conjunction with the X-ray structural results to establish the preferred protonation site of the thiadiazole ring.
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    Crystal structure of pyridinium hydrogen sulfate, [HC5H5N][HSO4] (1994)
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    Journal of chemical crystallography 24 (1994), S. 285-287 
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    Structures of Z-(nitrostilbene)chromium tricarbonyl complexes: The effect of metal coordination on the nonplanarity of the stilbene system (1994)
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    Journal of chemical crystallography 24 (1994), S. 315-320 
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    Notes: Abstract The structures of the nitrostilbene complexes Z-(4-R−C6H4−CH=CH−C6H4-4′-NO2)Cr(CO)3 (R=Me2N,1; H,2; F3C,3), are reported. The copounds were prepared as part of a study of the synthesis of organometallic complexes with potential nonlinear optics applications. For Z-(4-Me2N−C6H4−CH=CH−C6H4-4′-NO2)Cr(CO)3,1, triclinic, $$P\bar 1$$ ,a=7.214 (3) Å,b=7.340 (3) Å,c=17.238 (9)Å, α=88.23 (5)°, β=88.76 (4)°, γ=87.66 (3) °,Z=2. For Z-(C6H5−CH=CH−C6H4-4′-NO2)Cr(CO)3,2, monoclinic, P21/C,a=12.255 (3) Å,b=9.415 (1) Å,c=13.579 (4) Å, β=105.60 (2)°,Z=4. For Z-(4-F3C−C6H4−CH=CH−C6H4-4′-NO2)Cr(CO)3,3, triclinic, $$P\bar 1$$ ,a=7.094 (2) Å,b=8.057 (5) Å,c=17.295 (9) Å, α=87.95 (5)° β=85.94 (4)°, γ=64.24 (5)°,Z=2. The structural data show that the Z isomers exhibit bond lengths and angles similar to those observed in the E isomers, but the stilbene fragment is considerably more nonplanar. As a consequence, these molecules are unlikely to behave as NLO materials.
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    Crystal structures of 1-(2-hydroxyphenyl)-3-phenyl-1,3-propanedione and 1-(1,3-benzodioxol-5-yl)-3-(2,4-dimethoxyphenyl)-1,3-propanedione (1994)
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    Journal of chemical crystallography 24 (1994), S. 331-335 
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    Notes: Abstract 1-(2-Hydroxyphenyl)-3-phenyl-1,3-propanedione crystallizes in the triclinic space group $$P\bar 1$$ (a=5.4233(5),b=13.910(1),c=17.036(1) Å, α=68.311(6), β=80.854(7), γ=78.760(8)°) as two independent enolic tautomers in which the hydroxyl and phenolic protons are hydrogen bonded to the ketonic oxygen atom. The structure was refined toR=0.039 for 2085I≥3σ(I) reflections. 1-(1,3-Benzodioxol-5-yl)-3-(2,4-dimethoxyphenyl)-1,3-propanedione, which belongs to the triclinic $$P\bar 1$$ space group (a=7.3990(7),b=8.1239(5),c=14.004(1) Å, α=86.673(6). β=88.574(7), γ=64.885(7)°) also exists in the enolic form. The structure was refined toR=0.040 for 1564I≥3σ(I) reflections.
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    Future contributions to Journal of Chemical Crystallography (1994)
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    Journal of chemical crystallography 24 (1994), S. 353-353 
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    Solid-state structures and conformational studies of four 1,2,3,4-tetrahydroacridine Alzheimer's disease therapeutics (1994)
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    Journal of chemical crystallography 24 (1994), S. 301-310 
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    Notes: Abstract The solid-state structures of four 1,2,3,4-tetrahydroacridines [tacrine hydrochloride monohydrate (1), 7-methoxytacrine hydrochloride monohydrate (2), velnacrine hydrogenmaleate (3) and suronacrine hydrogenmaleate (4)] were determined from single-crystal X-ray diffraction analysis. (1): monoclinic,P21/n, a=8.778(1),b=8.521(1),c=17.603(2)Å, β=101.34(1)°. (2): monoclinic,C2/c, a=12.326(7),b=18.050(9),c=13.822(8)Å, β=113.70(4)°. (3): triclinic, $$P\bar 1$$ ,a=7.349(2),b=9.417(3),c=12.557(4)Å, α=109.62(2), β=98.12(2), γ=101.18(2)°. (4): monoclinic,P21/n, a=8.513(6),b=18.74(1),c=13.401(6)Å, β=91.21(5)°. FinalR factors for compounds(1)–(4) are 0.047, 0.057, 0.057, 0.11, respectively. The overall arrangement of the common aminotetrahydroacridine skeleton looks similar in all derivatives. However, whereas enantiomerization of the unsubstituted cyclohexenyl rings occurs in (1) and (2), onlyquasi-axially hydroxyl substituted diastereomers are found for (3) and (4). This is presumably due to the different propensities for hydrogen bonding of axially vs. equatorially disposed hydroxyl groups with the hydrogenmaleate anions. Empirical and semiempirical calculations were performed to examine the conformational behavior of the four compounds, bothin vacuo and in solution.
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    Crystal structure ofcatena-O,O′-diethylphosphonoacetatotriphenyltin (1994)
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    Journal of chemical crystallography 24 (1994), S. 337-340 
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    Notes: Abstract Triphenyltin diethylphosphonoacetate, which crystallizes in the monoclinc space groupP21/c (a=15.154(4),b=9.159(3),c=17.685(4) Å, β=91.410(8)°), adopts a polymeric structure in which planar triphenyltin cations (∑C—Sn—C=357.3(6)°) are axially linked by the diethylphosphonoacetato anions (Sn−Oesteryl=2.129(3), Sn←Ophosphoryl=2.420(3) Å; O−Sn←O=171.9(1)° into chains that propagate by translations along theb-axis. The structure has been erfined toR=0.037 for 3384I≥3σ(I) reflections.
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    Crystal structures of N-(2-aminoethyl)-1-naphthaleneneacetamide nitrate and hydrogen tartrate dihydrate (1994)
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    Journal of chemical crystallography 24 (1994), S. 391-395 
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    Notes: Abstract Nitrate (1): C14H17N2O+·NO 3 − , orthorhombic, Pbca,Z=8,a=9.6924(4),b=27.664(2) andc=10.8589(6)Å.Hydrogen tartrate dihydrate (2): C14H17N2O+·C4H5O 6 − ·2H2O, orthorhombic, P212121,Z=4,a=7.6703(5),b=7.9368(4) andc=31.953(2)Å. In the solid state, cation conformation differ due to molecular flexibility, very different anionic environments, and resultant hydrogen bonding patterns. Despite these differences, the two structures maintain the same separations (about 7.35 Å) of the two most distant potential pharmacophoric groups, i.e., the aromatic ring and the protonated amine group.
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    Structure of bis(2-pyridine-N-oxide) diselenide and its formation from tetraphenylantimony(V)selenopyridine-N-oxide (1994)
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    Journal of chemical crystallography 24 (1994), S. 421-423 
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    Keywords: Bis(2-pyridine-N-oxide) diselenide
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    Notes: Abstract The structure of bis(2-pyridine-N-oxide) diselenide was determined by single crystal X-ray diffraction. The compound crystallized in the triclinic system and the structure was solved in the space group $$P\bar 1$$ . The lattice constants were determined to bea=7.174(2),b=7.176(2),c=11.070(2) Å, α=87.67(2)°, β=73.68(2)°, and γ=89.57(2)°;Z=2,D x=1.906 Mg m−3. The final least squares refinement based on 1942 independent observed reflections yieldedR=0.033,wR=0.044. The Se−Se′ bond length is 2.326(1) Å and each Se is coordinated to the O atom of the corresponding N-oxide moiety at a distance of about 2.6 Å.
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    The crystal structure of calcium succinate monohydrate (1994)
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    Journal of chemical crystallography 24 (1994), S. 437-440 
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    Keywords: Ca(C4H4O4)·H2O ; pentagonal pyramid ; calcium succinate ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The crystal structure of calcium succinate monohydrate, Ca(C4H4O4)·H2O, has been determined by single crystal X-ray diffraction. The crystals are monoclinic witha=11.952(2),b=9.691(2),c=11.606(2)Å, β=108.81(1)°, space group C2/c,Z=8,V=1272.49 Å3,d m =1.80, andd c =1.818 Mg m−3. The structure was refined by full-matrix least-squares techniques toR=0.027,R w =0.040, for 829 reflections with1≥3δ(I). Ca is coordinated to seven oxygen atoms, and the coordination polyhedron is best described as a pentagonal bipyramid. One carboxylate group in the succinate ion is bonded to three different Ca ions, forming a four-membered chelate ring with one Ca ion is bonded to three different Ca ions, forming a four-membered chelate ring with one Ca ion and unidentate bridge bonds to two other Ca ions. The other carboxylate group is bonded to two Ca ions through unidentate bonds. The structure is highly polymeric. The general structural features are nearly identical to those of calcium adipate monohydrate.
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    Molecular structure ofrac-(4R*,4aS*,10aS*)-4-nitro-1,2,3,4,4a,9,10,10a-octahydrophenanthren-4a-ol, an unusual by-product of nitration of a crude 9,10-dihydrophenanthrene (1994)
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    Journal of chemical crystallography 24 (1994), S. 451-455 
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    Keywords: C14H17NO3 ; chair ; half-chair
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract A new nitro-octahydrophenanthrenol has been isolated by nitration of a crude 9,10-dihydrophenanthrene, which was identified by nmr and X-ray diffraction analysis. Crystallographic and molecular structure confirmed the compound as therac-(4R*,4aS*,10aS*)-4-Nitro-1,2,3,4,4a,9,10,10a-octahydrophenanthren-4a-ol. The crystal was triclinic, $$P\bar 1$$ ,a=10.549(3),b=8.530(3),c=7.131(1)Å, α=107.07(3), β=91.62(3), γ=96.27(4)°. Cyclohexane and cyclohexene rings aretrans-fused and have chair and half-chair conformations, respectively. The molecules are associated by hydrogen bridge between the hydroxyl oxygen and both nitro oxygens.
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    Crystal structure of bis(triphenylphosphine)iminium p-tolylsulfonate, [(PPh3)2N+][CH3C6H4SO 3 − ] (1994)
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    Journal of chemical crystallography 24 (1994), S. 473-476 
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    Keywords: [(PPh3)2N+][CH3C6H4SO 3 − ] ; staggered conformation
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    Inclusion compounds of N,N,N′,N′-tetraisopropylfumaride with isomers of methyl phenol and water (1994)
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    Journal of chemical crystallography 24 (1994), S. 495-501 
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    ISSN: 1572-8854
    Keywords: Structural isomers ; enclathration ; inclusion compounds
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    Notes: Abstract The crystal structures and thermal analyses of the host compound, N,N,N′,N′-tetraisopropylfumaride, witho-cresol,m-cresol and water are reported and compared to that of thep-cresol complex previously reported in an attempt to elucidate the reasons for host selectivity.
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    Preparation, spectral studies and X-ray crystal structure of 1,3,5-triphenyl-1,5-pentanedione, C23H20O2 (1994)
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    Journal of chemical crystallography 24 (1994), S. 511-515 
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    ISSN: 1572-8854
    Keywords: C23H20O2 ; diketone ; cis arrangement
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    Notes: Abstract 1,3,5-triphenyl-1,5-pentanedione, C23H20O2, has been prepared and characterized by spectroscopic methods and single crystal X-ray analysis. Crystals are monoclinic, space groupP21/n, a=28.124(4),b=5.997(1),c=10.434(1)Å, β-98.42(1)Å,Z=4. The structure has been refined to a finalR-value of 0.040 for 1625 reflections withF o〉3σ(F o). The compound contains the two carbonyl groups in a mutuallycis arrangement.
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    Crystal structures of 2-phenyl- and 2-benzyl-5,6-dihydro-6-hydroxy-7H-1,2,4-triazolo [3,2-b] 1,3-thiazines (1994)
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    Journal of chemical crystallography 24 (1994), S. 527-530 
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    ISSN: 1572-8854
    Keywords: X-ray structure ; conformation ; 1,2,4-triazolo[3,2-b]1,3-thiazines
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    Notes: Abstract The examined compounds crystallize in the monoclinic space groupsP2 1/c (phenyl derivative,1) andP2 1/a (benzyl derivative,2). The unit cell parametersa, b, c (Å) and β (°) were: 6.402(1), 16.506(1), 10.144(1), 97.48(1) for1 and 12.099(2), 4.612(1), 21.712(4) and 105.20(2) for2. The finalR(Rw) factors were 0.043 (0.041) and 0.121 (0.126) for1 and2, respectively. Both molecules have similar geometry of the bicyclic system with flat 1,2,4-triazole rings, sofa conformations of 1,3-thiazole ones and axial hydroxy groups. In the crystals the molecules form infinite chains (by means of O−H...N(4) hydrogen bonds), enantiomeric in1 and racemic in2.
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    Inclusion compounds of N,N,N′,N′-tetracyclohexylfumaride with isomers of cresol and water (1994)
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    Journal of chemical crystallography 24 (1994), S. 545-552 
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    Keywords: Inclusion compounds
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    Notes: Abstract The crystal structures and thermal analyses of the host compound, N,N,N′,N′-tetracyclohexylfumaride, witho-cresol,p-cresol and water are reported and compared to that of them-cresol complex previously reported in an attempt to elucidate the reasons for host selectivity.
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    Synthesis and structure of 1,10-phenanthroline bis {2-[(2-pyrrole) methylimino]phenolato}cobalt(II) (1994)
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    Journal of chemical crystallography 24 (1994), S. 469-472 
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    ISSN: 1572-8854
    Keywords: [Co(C11H9N2O)2(C12H8N2)] ; Schiff bases
    Source: Springer Online Journal Archives 1860-2000
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    Structural and electrochemical characterization of 1,3-bis-(4-methylphenyl)imidazolium chloride (1994)
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    Journal of chemical crystallography 24 (1994), S. 489-493 
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    ISSN: 1572-8854
    Keywords: Imidazolium ; carbenes ; sodium hydride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of 1,3-bis(4-methylphenyl)imidazolium chloride was determined and compared to its related imidazole-based carbene. The important structural difference is the greater N2−C2−N3 angle in the salt (109.6°) than in the carbene (101.2°). An electrochemical investigation of the salt revealed a single reduction at −2.32 V in the forward scan and two oxidations at −0.89 and −0.54 V following scan reversal.
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    Crystal structure of two oximes incis-pinane series (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 503-506 
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    ISSN: 1572-8854
    Keywords: Oximes ; cis-pinane series ; amino alcohols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structures of racemic 2α-hydroxy-4-hydroxyiminopinan-3-one (1) and 3-hydroxyimino-cis-pinan-4-one monohydrate (2) have been determined by X-ray diffraction. The crystals of1 are monoclinic:P21/c, a=7.838(2),b=10.776(3),c=12.025(3) Å, β=105.09(1)°,Z=4, room temp.; the crystals of2 are orthorhombic;P212121,a=8.181(3),b=9.250(3),c=14.085(6)Å,Z=4, T=80K. Both structures were solved by direct methods, and refined toR=0.037 for 1920 reflections (1) and 0.032 for 1776 reflections (2). The absolute configuration of2 was not established. The hydroxyimine groups in both crystals and water molecules in2 participate in the network O−H...O of hydrogen bonds.
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    Molecular structure of isopropyl 1-phenyl-4-phenylhydrazono-5-oxo-3-pyrazolecarboxylate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 517-520 
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    ISSN: 1572-8854
    Keywords: Azopyrazolone dye ; C19H18N4O3 ; tautomeric forms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The new azopyrazolone dye has been synthesized and its crystal structure has been investigated. Crystals of C19H18N4O3 are triclinic: $$P\bar 1$$ ,a=7.484(1),b=10.646 (1),c=11.897(1) Å, α=82.28(1), β=72.86(1), γ=86.83(1)°,Z=2. The structure has been solved by direct methods and refined by full-matrix least-squares techniques toR=0.050 for 2622 unique reflections. The tautomeric form of the molecules has been determined as a hydrazo form. Delocalization of the C5=O3 and C4=N3 π-electrons and delocalization of the lone-pair electrons of N1, N3, and N4 atoms has been observed. The intramolecular N−H...O hydrogen bond forms the six-membered ring C2N2H...O condensed with the pyrazolone ring. The molecules are connected by intramolecular C−H...O hydrogen bonds.
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    Primary to secondary sphere coordination of 15-crown-5 to lanthanide(III) chlorides: structural analysis of [MCl3(15-crown-5)] (M=La, Ce) and [Er(OH2)8]Cl3·15-crown-5 (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 531-537 
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    ISSN: 1572-8854
    Keywords: Lanthanum chloride ; cerium chloride ; erbium chloride ; 15-crown-5 ; complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Complexes of LaCl3·7H2O and CeCl3·7H2O directly coordinated to 15-crown-5 were prepared by placing the reactants in 3∶1 CH3CN∶CH3OH on opposite sides of a fine porosity glass frit in a U-shaped cell and passing a 10 μA current through the cell. The crystal structures of the two anhydrous 8-coordinate complexes, [MCl3(15-crown-5)] (M=La, Ce) have been determined. Each contains the lanthanide in a bicapped trigonal prismatic geometry. The two complexes are isostructural crystallizing in the monoclinic space groupP21/c with (at 20°C) for M=La:a=8.217(8),b=14.298(2),c=14.341(9) Å, β=104.79(8)°, andD calc=1.90 g cm−3 forZ=4; for M=Ce:a=8.208(9),b=14.263(6),c=14.270(8) Å, β=104.74(7)°, andD calc=1.92 g cm−3 forZ=4. Direct reaction of ErCl3·6H2O with 15-crown-5 in 3∶1 CH3CN∶CH3OH resulted in the crystallization of the second sphere hydrogen bonded complex [Er(OH2)8]Cl3·15-crown-5. This complex is monoclinic,P21/n with (at 18°C)a=9.193(3),b=17.235(9),c=15.216(5) Å, β=92.48(3)°, andD calc=1.76 g cm−3 forZ=4. The Er3+ ion is dodecahedral.
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    Synthesis and characterization of ternary L-histidine complexes. Crystal structure of (2,2′-dipyridyl)-(L-histidinato-N,N′,O)copper(II) perchlorate 1.5 hydrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 567-571 
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    ISSN: 1572-8854
    Keywords: Ternary complexes ; copper(II) ; cobalt(II) ; zinc(II)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A series of ternary complexes of copper(II), cobalt(II) and zinc(II) with L-histidine, 1,10-phenanthroline, 2,2′-dipyridyl or imidazole having perchlorate or acetate as counterions were synthesized and characterized by conventional methods and for [Cu(bipy)(L-hist)]ClO4·1.5H2O and X-ray crystal structure was determined. The crystals belong to the monoclinic space groupC2 witha=18.843(3),b=10.582(2),c=11.020(2)Å, β=115.20(10)°,Z=4,R=0.0535. The structure is consistent of [Cu(bipy)(L-hist)]+ cations, perchlorate ions and water molecules. The geometry around copper is trigonal bipyramidal with one N,N′,O tridentate L-histidine molecule and one 2,2′-dipyridyl ligand, the apical sites are occupied by the α-amino nitrogen [Cu−N(71) 1.995(8)Å] and by N(11) of 2,2′-dipyridyl [Cu−N(11) 1.983(7)Å], the equatorial plane is formed by the N(3) imidazole δ-nitrogen [Cu−N(3) 2.140(6)Å], O(82) carboxylic oxygen [Cu−O(82) 2.009(5)Å] and N(22) [Cu−N(22) 2.010(7)Å].
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    Structural study of thiosaccharin by single crystal X-ray diffraction and infrared spectroscopy (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 581-586 
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    ISSN: 1572-8854
    Keywords: Thiosaccharin ; infrared spectra ; crystal structure polymorphs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of thiosaccharin (1,2-benzisothiazol-3(2H)-thione 1,1-dioxide) has been investigated by X-ray diffraction and infrared spectroscopic methods. The compound crystallizes in the orthorhombic space groupFdd2 witha=26.591(3),b=25.058(3),c=4.934(5) Å,Z=16. The structure consists of thiosaccharin molecules bonded to each other through N−H...O intermolecular hydrogen bonds. The infrared spectra of the thiosaccharin at room and liquid-nitrogen temperature were recorded. The spectral features in the N−H stretching region were correlated with the crystallographic data on the geometry of the N−H...O hydrogen bonding. In an attempt to assign the bands due to the SO2 stretching modes, the spectrum of thiosaccharin was compared with that of saccharin (1,2-benzoisothiazole-3(2H)-one, 1,1-dioxide).
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    Structure of the dipeptide L-lysine-L-leucine·Acetate, 0.5 acetic acid hemihydrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 597-602 
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    ISSN: 1572-8854
    Keywords: Lysine ; Leucine ; Dipeptide structures ; X-ray crystallography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2(C12H26O3N3·C2H3O2)·C2H4O2·H2O,M r =350.44, triclinic, P1,a=5.576,b=12.574(3),c=14.946(2) Å, α=107.80(2), β=96.34(2), γ=89.89(2)°.B=991.04(6) Å3,Z=2,D x =1.201 g/cm3, λ(KαCu)=1.5418, Å, μ=7.4 cm−1, room temperature.R=0.074 for 2645 observed reflections. In the unit cell there are two peptide molecules, three acetic acid molecules, two of them likely to be present as acetate anions, and one water molecule. Each peptide exists in zwitterionic form with the carboxylic group deprotonated, and with positive charges both in the amino terminal and ∈-amino groups of lysine. The two peptide molecules have almost identical conformations. The dipeptide backbone is folded.
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    Crystal structure of bis-N,N′-p-chlorosalicylideneamine-1,2-diaminobenzene (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 603-606 
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    ISSN: 1572-8854
    Keywords: Schiff-bases ; Molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of the title compound, C20H14N2O2Cl2, has been determined by single crystal X-ray diffraction techniques. It crystallizes in the orthorhombic system witha=7.532(3)Å,b=18.563(2)Å,c=25.089(3)Å, space groupPbca,V=3507.9(3)Å3,Z=8,F(000)=1584.D x =1.459 g cm−3,M=385.3 a. m. u., λ (MoKα)=0.7107 Å, μ=3.35 cm−1,T=297°K,R=0.086,R w =0.049 for 2119 unique diffractometer data. The molecules are linked by van der Waals forces.
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    Synthesis, crystal and molecular structure and vibrational characterization of N,N-dimethyl-oxathioamidate monohydrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 615-620 
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    ISSN: 1572-8854
    Keywords: (SO2NC4H6) ; metal(II) complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound (SO2NC4H6) has been prepared and characterized by X-ray diffraction and infra-red and Raman spectra. The structure has been refined using single-crystal X-ray diffraction data measured at 295K [MoKα-radiation with λ=0.71073 Å]. The crystals are monoclinic, space groupP21/n,Z=4,a=6.240(2),b=6.786(2),c=19.988(1)Å, γ=108.47(2)°,V=802.8(7)Å3.D calc.=1.566 Mg m−3,F(000)=392, μ=8.582 cm−1. The final agreement factors for 1906 observed refections [I〉3σ(I)] were:R=0.030 andR w=0.043. The dihedral angle between de C−C−S−N plane and the C−C−O−O plane is 88.31(4). The potassium atom within the title compound structure has a slightly distorted trigonal bipyramidal coordination. Infrared and Raman spectra of the normal CH3/CD3 and H2O/D2O isotopes and the waterfree compounds at different temperatures made it possible to perform isotopes complete vibrational analysis and clearly shows the very special hydrogen bonded water molecule in the crystal.
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    Structure of a platinum(II) complex containing a benzothiazole derivative: [NEt4][Pt(3,4-dsb)Br3] (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 639-642 
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    ISSN: 1572-8854
    Keywords: Platinum(II) ; benzothiazole derivative ; antitumor activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Tetraethylammoniumtribromo[2-(3′.4′-dimethoxy)styrylbenzothiazole]platinate(II), [(C2H5)4N]-[PtBr3(C17H15NO2S)], monoclinic,P21/c,a=13.454(7),b=11.991(3),c=19.004(5) Å, β= 108.92(3)°,V=2900(4) Å3,Z=4,D r=1.975 g cm−3, λ(MoKα)=0.71073 Å, μ=95.59 cm−1,F(000)=1656,T=303 K, finalR=0.051 for 2262 unique observed reflections. The structure was solved by heavy atom and Fourier methods. The molecule is nearly planar, with a dihedral angle of only 3.57(7)° between the benzothiazole and phenyl rings. The C−S−C angle in the thiazole ring is 91(1)°.
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    Crystal and molecular structure of 647-1647-1647-13,6,14,16,20-pentaacetate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 647-651 
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    ISSN: 1572-8854
    Keywords: Grayanotoxins ; skeletal transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
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    Error estimates in the determination of rigid body displacements in protein crystals (1994)
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    Journal of chemical crystallography 24 (1994), S. 1-3 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We report the estimation of random errors in the refinement of the rigid body displacements of the α-helices of the enzyme 6-phosphogluconate dehydrogenase. Least-squares refinement of the TLS parameters of the helices has been carried out using X-ray reflection data of 2.1 Å resolution, resulting in anR-factor of 19.5%. Standard deviations were estimated from the normal matrix. The results show that the translational mean-square displacements of nearly all the helices are significant at this resolution. However the libration parameters are only significant when the helices have at least four turns. Screw-rotation tensor values cannot be determined at this resolution.
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    Determination and correlation of heavy atom positions in the derivatives used in the X-ray analysis of ribonuclease A at 2.5 Å resolution (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 37-49 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The analysis of four heavy atom derivatives of ribonuclease A is described leading to isomorphous phasing at 2.5 Å resolution. Differences in the characteristics of the derivatives are discussed with respect to the determination of their heavy atom parameters and the correlation of sites between derivatives to produce a self consistent set. The criteria used to ensure consistency are described. In the final phase analysis using refined heavy atom parameters the least squaresR factors of the derivatives were .124, .143, .101, and .067 respectively, and the mean figure of merit for the 3444 observed reflexions was 0.66.
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    Reaction of trimethylaluminum and trimethylgallium with bifunctional amines: Syntheses and molecular structures of [Me2Al−N(CH2CH2)2−C−(OCH2)2]2 and [Me2Ga−N(Si(H)Me2)2]2 (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 61-65 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystalline products [Me2Al−N(CH2CH2)2−C−(OCH2)2]2 (I) and [Me2Ga−N(Si(H)Me2)2]2 (II) were prepared from reactions of trimethylaluminum and trimethylgallium with 1,4-dioxa-8-azaspiro[4.5]-decane and 1,1,3,3-tetramethyldisilazane, respectively, in toluene. The organoaluminum dimer crystallizes in the monoclinic space groupP21/c with unit cell parametersa=8.970(2) Å,b=9.683(2) Å,c=12.833(3) Å, β=103.18(2)°,V=1085.3(3) Å3, andD calcd=1.22 g cm−3 forZ=2. Least-squares refinement based on 935 observed reflectionsI〉3σ(I) in the range 3.5°〈2ϑ〈45.0° led to a finalR factor of 0.033 (R w =0.041). The dimeric organosilazagallium crystallizes in the triclinic space group $$P\bar 1$$ with unit cell parametersa=7.636(2) Å,b=9.168(2) Å,c=9.466(3)Å, α=72.81(2)°, β=87.94(2)°, γ=69.90(2)°,V=593.0(3) Å3, andD calcd=1.30 g cm−3 forZ=1. Least-squares refinement based on 1661 observed reflectionsI〉3σ(I) in the range 3.5°〈2ϑ〈48.0° led to a finalR factor of 0.055 (R w =0.070). Both compoundsI andII reside about a crystallographic center of symmetry and contain a planar M2N2 (M=Al forI, Ga forII) four-membered ring withI having an Al...Al contact of 2.801 Å.
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    Crystal structure of 14, α-hydroxy, sandarocopimar-7, 15-diene-19-oic acid (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 79-82 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract C20H30O3, M r =318.46, Monoclinic,P21,a=12.232(2) Å,b=11.491(2) Å,c=14.160(3) Å, β=115.2°(3),V=1800.3(7) Å3,Z=4,D x =1.18 Mg m−3, λ(CuKα)=1.5418 Å, μ=5.3 cm−1,F(000)=696,T=298 K. FinalR=0.044 for 2645 reflections withI〉2σ. The two crystallographically independent molecules in the unit cell adopt essentially similar conformations. The structure reveals atrans relationship between the hydrogen at C(9) and the methyl group at C(20). The stereochemistry at C(13) is S. Apart from van der Waals forces the structure is stabilized by hydrogen bonds.
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    Crystal structure of Pt(S2COEt)2 (1994)
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    Journal of chemical crystallography 24 (1994), S. 711-714 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; platinum ; xanthate ; square planar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystals of Pt(S2COEt)2 are orthorhombic, Pbca, with (at 20°C)a=7.799(3),b=7.368(6),c=20.588(7) Å,D cale=2.46g cm−3 forZ=4. The platinum atom resides on a crystallographic center of inversion and is bound to the four sulfur atoms of the xanthato ligand in a square planar geometry. The Pt−S distances are 2.313(6) and 2.320(7) Å with an intraligand S−Pt−S angle of 75.1(2)°.
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    Future contributions toJournal of Chemical Crystallography (1994)
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    Journal of chemical crystallography 24 (1994), S. 719-719 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
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    Synthesis, structure and IR characterization of disodium tetra(9,10-dihydro-9-oxo-10-acridineacetato)zincate(II) bis(ethanol) heptahydrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 731-737 
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    ISSN: 1572-8854
    Keywords: Synthesis ; crystal structure ; IR data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis, crystal structure and IR data are reported for Na2[Zn(CMA)4]·2EtOH·7H2O, where CMA− is the 9,10-dihydro-9-oxo-10-acridinacetate ion. The complex crystallizes in the monoclinic space group P2/n, with cell dimensionsa=17.335(9),b=8.440(5),c=21.875(12) Å, β=91.94(5)°,Z=2. The structure was solved by direct methods and refined to a finalR value of 0.0363 for 3022 non-zero reflections. The Zn2+ ion occupies twofold axis and is coordinated to four carboxylate ligands, the ZnO4 tetrahedron is considerably distorted with Zn−O distances of 1.978(3) and 1.961(3)Å. Each Na+ cation interacts with two water, one ethanol, and three carboxylate O atoms comprising distorted octahedron. The Zn2+ and Na+ cations are linked through monooxygen and syn-syn carboxylate bridges forming a trinuclear, mixed-metal cluster. The Zn...Na separation is 3.267(2)Å and Na...Na distance equals 3.520(2)Å. All oxygen bonded H-atoms are utilized in hydrogen bonds. The acridone rings overlap in the crystal with the 3.5 Å interlayer separations. The compound has been characterized by IR spectroscopy.
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    Molecular complexes of sulfonamides. 3. Structure of 5-methoxysulfadiazine (form II) and its 1∶1 complex with acetylsalicylic acid (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 695-701 
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    ISSN: 1572-8854
    Keywords: Molecular complexes ; sulfonamides ; acetylsalicylic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray structure of the biologically most active polymorph (Form II) of 5-methoxysulfadiazine (1) and that of the 1∶1 complex between this sulfonamide and acetylsalicylic acid (2) are reported. The polymorph1 is monoclinic, space groupP21/c witha=13.086(2) Å,b=5.583(1) Å,c=17.222(3) Å, β=99.98(1)°,Z=4 and occurs as centrosymmetric hydrogen bonded (N−H...N) dimers in the crystal. This arrangement differs from that observed in other polymorphs of the drug. Complex2 is triclinic, $$P\bar 1$$ ,a=8.102(1)Å,b=12.033(1) Å,c=12.170(2) Å, α=111.67(1)°, β=93.77(1)°, γ=103.82(1)°,Z=2. Complexation involves linear intermolecular hydrogen bonds, N−H...O=C and N...O−H, between the amide group and pyrimidinyl N atom of the sulfonamide and the carboxylic group of the acetylsalicylic acid. On complexation to form2, neither molecular component undergoes any major structural change.
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    Crystal and molecular structure of 2,6-dihydroxybenzoic acid (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 703-705 
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    ISSN: 1572-8854
    Keywords: 2,6-dihydroxybenzoic acid ; hydrogen bond ; carboxylic acid dimer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of 2,6-dihydroxybenzoic acid has been determined by single crystal X-ray diffraction. The crystals are monoclinic witha=5.4084(5),b=5.2240(7),c=22.986(4) Å, β=94.69(3)°, space group P21/c,Z=4,V=647.27(16) Å3,d c =1.58Mg m−3, The acid crystallizes as hydrogen bonded carboxylic dimers which pack to generate a herringbone motif of the type typically encountered in polycyclic aromatic compounds.
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  • 86
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    The structure of dimethylcrocetin (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 739-742 
    Details
    ISSN: 1572-8854
    Keywords: Dimethylcrocetin (DMCRT) ; carotenoids ; structure ; saffron ; Crocus sativus L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of dimethylcrocetin (DMCRT), prepared by alkaline hydrolysis in methanol of the glucosidic carotenoids extracted from the stigmata of theCrocus sativus L. flowers, has been determined. The molecule has the all-trans configuration and is planar forming a long conjugated system. The C−O bond length values of the two ester groups are shortened as expected. The compound (C11H14O2)2 crystallizes in the orthorhombic space group Pbcn witha=12.5907(7),b=7.5639(5) andc=21.963(2)Å. Dimethylcrocetin has characteristic Infrared absorptions at 1697 cm−1 ϑ (C=O) and 1229 cm−1 ϑ (C−O) and characteristic Raman vibrational modes at 1542 cm−1 ϑ (C=C) and 1166 cm−1 ϑ (C−C).
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    URL: http://dx.doi.org/10.1007/BF01666962
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  • 87
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    The structure of ethyl allyl 1,4-dihydro-2,6-dimethyl-4-[4-(4H-4-oxo-1-benzopyran-2-yl)phenyl]-3,5-pyridine dicarboxylate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 747-751 
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    ISSN: 1572-8854
    Keywords: 1,4-DHP ; calcium antagonistic activity ; nifedipine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the title compound has been determined by direct methods, and refined to a finalR of 0.070 for 1466 observed reflections. The compound crystallizes in space group P2l/n with cell dimensionsa=10.706(8),b=21.127(11),c=12.038(10) Å, Z=4.1,4-dihydropyridine ring adopts a boat shaped conformation. The flavon molecule is planar and it's phenyl ring is almost perpendicular to the 1,4-DHP. The C36 atom of the allyl group shows disorder.
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    URL: http://dx.doi.org/10.1007/BF01666964
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  • 88
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    Crystal structure and low-temperature emission of [(dmp)Cu(μ-S2butphos)2Cu(dmp)][BF4]2·6CH2Cl2 (dmp=2,9-dimethyl-1,10-phenanthroline; S2butphos=1,4-bis(diphenylphosphinesulfido)butane) (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 753-758 
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    ISSN: 1572-8854
    Keywords: Cu(I) phosphine sulfide complex ; intramolecular π-stacking ; phosphine moieties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis and crystal structure of a bimetallic luminescent Cu(I) complex containing 1,4-bis(diphenylphosphinesulfido)butane and the α-diimine 2,9-dimethyl-1,10-phenanthroline (dmp) is described. The coordination geometry about the Cu(I) center is pseudo-tetrahedral. Interplanar interactions between phenyl groups on the phosphine sulfide ligands and the phenanthroline exist which are indicative ofintramolecular π-stacking, leading to compressed S−Cu−S bond angles. The complex displays emission from a single metal-centered charge-transfer state at 77 K in a 4∶1 ethanol/methanol (v/v) glass. This is in contrast to the triphenylphosphine complex, which exhibits dual luminescence from a charge-transfer and an intraligand state at 77 K. Crystal data: triclinic, $$P\bar 1$$ ,a=13.619(4) Å,b=13.673(2) Å,c=15.384(2) Å, α=75.08(1)°, β=80.35(2)°, γ=80.67(2)°.
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    URL: http://dx.doi.org/10.1007/BF01666965
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  • 89
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    Structure, absolute configuration, and conformation of a fused complex cyclic carbohydrate from a cameroon plant extract (CAMT2) (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 775-781 
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    ISSN: 1572-8854
    Keywords: Folk Medicine ; Limonoid ; Antimalarial ; Immunomodulator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the natural product C29H38O9, an extract from a Cameroonian plant, has been determined by direct methods. Crystals are orthorhombic, P212121,a=24.571(4),b=16.398(3),c=13.778(4) Å,Z-8,D c=1.270 mg/m3. The final R-factor for 2892 reflections withI〉2σ(I) is 0.0531. The two molecules forming the asymmetric unit have very similar molecular geometry. each molecule comprising a nucleus of six fused rings B to G: where B=pyranyl, C=pyranyl, D=furanyl, E=cyclohexene, F=pyranyl, G=cyclohexyl. Ring B also has a furanyl side-group (ring A). The ring conformations in both molecules are: A (1/2-chair/envelope); B(envelope); C(envelope); D(1/2-chair); E(1/2-chair); F(envelope); G(chair). In the cyclohexene ring E the substitution pattern is 2-hydroxy 3-methyl 5-dimethyl. The two molecules in the asymmetric unit are linked by two OH...O hydrogen bonds to form the crystal structure.
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    URL: http://dx.doi.org/10.1007/BF01668240
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  • 90
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    Crystal and molecular structure of di-μ-bromobromopentakis(benzimidazole)dicopper(II) monobromide tetrahydrate [Cu2Br3(C7H6N2)5]Br·4H2O (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 139-143 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new complex compound. [Cu2Br3(C7H6N2)5]Br·4H2O, has been synthesized and its crystal structure investigated by single-crystal X-ray methods. The crystals are isostructural with those of the [Cu2Cl3(C7H6N2)5]Cl·4H2O salt. They are orthorombic, space group Pnma with 4 formula units in a cell of dimensions:a+19.923(1),b+17.555(2),c+12.0523(4)Å. The structure was refined by full-matrix least-squares to giveR+0.047 andR w+0.053 for 3569 intensities above 3σ(I). As in the chloride compound, the complex cation consists of pairs of distorted trigonal bipyramidal Cu(II) centers which share an edge by two equatorial bromide ions. The Cu...Cu nonbonding distance in the complex in 3.4894(7)Å. The two Cu−Br−Cu bridges are not equivalent and their geometry is slightly different from that in the chloride complex. Comparison of the investigated structure to other binulear bis(μ-halide) bridged copper(II) complexes of similar structure has been made.
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    URL: http://dx.doi.org/10.1007/BF01833670
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  • 91
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    Synthesis and crystal structures of aluminum and iron phosphites (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 155-163 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The hydrated forms of aluminum and iron phosphite were prepared and their structure was solved using X-ray powder diffraction data. The diffraction data for the aluminum phosphite powder sample was collected using synchrotron radiation(λ=1.3087 Å) while that for iron phosphite was obtained from a rotating anode X-ray source. Both compounds crystallize in the monoclinic space group, P21. Unit cell parameters for the Al compound:a+8.0941(1),b+9.9137(1),c+7.6254(1) Å, β=111.95°; Fe compound:a+8.2548(1),b+10.1814(1),c+7.7964(1) (Å), β=111.94(1)°. The Rietveld refined formula is M2(PO3H)3·4H2O (M=Al, Fe). There are two independent metal atoms in the structure and both are six-coordinated. One of them is coordinated by two water molecules and four phosphite oxygens. The other atom is surrounded by one water molecule and five phosphite oxygens. All the phosphite oxygens are involved in bridging the Al atoms. The geometry about Al, Fe, and P atoms is normal and they display, expected bond parameters. The Lattice water is located in the cavity and is hydrogen bonded to phosphite oxygen and water molecules.
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    URL: http://dx.doi.org/10.1007/BF01833673
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  • 92
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    Future contributions to Journal of Chemical Crystallography (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 183-183 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01833678
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  • 93
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    Structural characterization of 2,6-bis(N-methylenepiperidino)-4-nitrophenol (MPN) and 2,6-bis-(N-methylenemorpholino)-4-nitrophenol (MMN)3 (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 187-191 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract MPN: C18H27N3O3,M r=333.43, monoclinic,P21/n. a=6.207(2),b=21.893(6),c=13.693(3) Å; β=96.12(2)o,V=1850.1(8) Å3.,Z=4,D cal=1.20 mg/m3,F(000)=720, λ (CuKα)=1.5418 Å, andT=298K.R=0.042 andwR=0.049 for 1675 observed reflections. MMN: C16H23N3O5,M r=337.38, triclinic,PĪ,a=9.642(1) Å,b=10.123(5) Å,c=9.341(2) Å, α=93.00(3)o, β=90.96(1)o, γ=110.46(1)o, V=852.5(5) Å3,D cal=1.31 mg m−3.F(000)=360,Z=2, λ(CuKα)=1.5418 Å,R=0.054 andwR=0.074 for 2804 observed reflections. The piperidine and morpholino rings assumechair conformation and orient each other at an angle of 44.8(1)o (MPN) and 47.1(1)o (MMN), respectively.
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  • 94
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    Electron crystallography of inorganic compounds. Direct determination of the basic copper chloride structure CuCl2·3Cu(OH)2 (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 219-224 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Experimental electron diffraction intensity data from basic copper chloride CuCl2·3Cu(OH)2 in its metastable form have been used for a direct structure analysis based on the evaluation of three and four phase structure invariants. The resultant electrostatic potential maps clearly show the correct atomic positions which correspond to those determined earlier by Voronova and Vainshtein (1958) from their interpretation of Patterson maps, and also to the X-ray analysis of the isostructural CuBr2·3Cu(OH)2 carried out by Aebi in 1948.
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    URL: http://dx.doi.org/10.1007/BF01672413
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  • 95
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    Crystal structure of 20ζ-hydroxy-3β-pyrrolidino-5-pregnene-16α-carbonitrile (HS1175): A novel design for neuromuscular blocking drugs (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 231-234 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of the title compound C26H38N2OH has been determined by direct methods from diffractometer data and refined by full-matrix least-squares. Crystals are monoclinicP21,a=6.237(1),b=10.295(2),c=18.485(2) Å, β=98.76(1)o,Z=2,D c=1.12 g cm−3,R=0.055 for 1059 observed reflections. The structure has two N-containing functional groups, one each in the pyrrolidine ring and carbonitrile groups, with interatomic separation of 11.527 Å. The 16-carbonitrile group is α-oriented. All steroid rings are trans-connected, A and C being in chair conformations and B and D half-charis. N(23) in the carbonitrile side-chair forms a weak tail-tail hydrogen-bond network by linking with the neighboring OH(20) hydroxy group at 1−x, 1/2+y, 1−z.
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    URL: http://dx.doi.org/10.1007/BF01672415
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  • 96
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    Synthesis and X-ray structures of [H3O+·18-crown-6] n [MCl 4 n− ]; (M=Fe,n=1;M=Co,n=2); compounds which form liquid clathrates with aromatic solutions (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 247-250 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compounds, [H3O+·18-crown-6][FeCl 4 − ] (1), and [H3O+·18-crown-6]2[CoCl 4 2− ] (2), were prepared by air oxidation of Fe(CO)5 for1, and Co2(CO)8 for2, in the presence of 18-crown-6, H2O and HCl(g) in toluene. Liquid clathrates formed immediately for both species:1·4.3 C7H8 and2·3.7 C7H8.1 crystallizes in the orthorhombic space group P21ma witha=10.357(1),b=11.824(1),c=8.961(1) Å, andD c=1.46 g cm−3 forZ=2. Refinement based on 935 observed reflections led to a finalR value of 0.089.2 crystallizes in the monoclinic space group C2/c witha=16.225(1),b=11.522(1),c=20.136(1)Å, β=97.75(2)o, andD c=1.37 g cm−3 forZ=4. Refinement based on 1322 observed reflections led to a finalR value of 0.11.
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    URL: http://dx.doi.org/10.1007/BF01670352
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  • 97
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    C−H...π(Ar)...H−C host-guest interactions in a novel air-stable cyanoborate clathrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 267-271 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The host compound forms a coordinato-clathrate in a coordination assisted host lattice. The host lattice is provided by hydrogen bonding between the nitrogen atom of the cyano group and two hydrogen atoms from the phosphonium methyl group. Guest molecules ofp-xylene occupy constricted channels in the lattice. The twop-xylene molecules participate in C−H...π(Ar)...H−C interactions. Results from searches of the Cambridge Structural Database for other C−H...π(Ar)...H−C and C−H...π(Ar) interactions are presented.
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  • 98
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    Structure of diethylenetriammonium nitrate (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 281-283 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
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    URL: http://dx.doi.org/10.1007/BF01670358
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  • 99
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    Future contributions toJournal of Chemical Crystallography (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 289-289 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
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    URL: http://dx.doi.org/10.1007/BF01670360
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  • 100
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    Crystal and molecular structure of 6-exo-methyl-6-endo-nitro-2-exo-phenylbicyclo[2.2.1]heptan-2-endo-ol (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 311-314 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The molecular and crystal structure of the title compound2, prepared in racemic form by addition of phenylmagnesium bromide to 6-exo-methyl-6-endo-nitrobicyclo[2.2.1]heptan-2-one (1) in the presence of cerium(III) chloride, were determined by single-crystal X-ray diffraction. The crystal selected for analysis was found to belong to the chiral orthorhombic space group P212121, witha=6.685(3),b=10.0788(5),c=18.581(1) Å. In the crystal, molecules of2 are associated by intermolecular hydrogen bonds between hydroxy and nitro groups (OH...O2N=0.82 Å).
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    URL: http://dx.doi.org/10.1007/BF01670206
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