ALBERT

Beschreibung: The terpenoid (−)-Istanbulin A is a natural product isolated from Senecio filaginoides DC, one of the 270 species of Senecio (Asteraceae) which occurs in Argentina. The structure and absolute configuration of this compound [9a-hydroxy-3,4a,5-trimethyl-4a,6,7,8a,9,9a-hexahydro-4H,5H-naphtho[2,3-b]-furan-2,8-dione or (4S,5R,8R,10S)-1-oxo-8β-hydroxy-10βH-eremophil-7(11)-en-12,8β-olide, C15H20O4] were determined by single-crystal X-ray diffraction studies. It proved to be a sesquiterpene lactone showing an eremophilanolide skeleton whose chirality is described as 4S,5R,8R,10S. Structural results were also in agreement with the one- and two-dimensional (1D and 2D) NMR and HR–ESI–MS data, and other complementary spectroscopic information. In addition, (−)-Istanbulin A is a polymorph of the previously reported form of (−)-Istanbulin A, form I; thus, the title compound is denoted form II or polymorph II. Structural data and a literature search allowed the chirality of Istanbulin A to be revisited. The antimicrobial and antifungal activities of (−)-Istanbulin A, form II, were evaluated in order to establish a reference for future comparisons and applications related to specific crystal forms of Istanbulins.

Beschreibung: Two conformational polymorphs of (N,N-dibutyldithiocarbamato-κ2 S,S′)[tris(3,5-diphenylpyrazol-1-yl-κN 2)hydroborato]cobalt(II), [Co(C45H34BN6)(C9H18NS2)] or [TpPh2Co(S2CNBu2)], 1, are accessible by recrystallization from dichloromethane–methanol to give orthorhombic polymorph 1a, while slow evaporation from acetonitrile produces triclinic polymorph 1b. The two polymorphs have been characterized by IR spectroscopy and single-crystal X-ray crystallography at 150 K. Polymorphs 1a and 1b crystallize in the orthorhombic space group Pbca and the triclinic space group P-1, respectively. The polymorphs have a trans (1a) and cis (1b) orientation of the butyl groups with respect to the S2CN plane of the dithiocarbamate ligand, which results in an intermediate five-coordinate geometry for 1a and a square-pyramidal geometry for 1b. Hirshfeld surface analysis reveals minor differences between the two polymorphs, with 1a exhibiting stronger C—H...S interactions and 1b favouring C—H...π interactions.

Beschreibung: A supramolecular complex, formed by encapsulation of C60 fullerene in a molecular container built from two resorcin[4]arene rims zipped together by peptidic arms hydrogen bonded into a cylindrical β-sheet, was studied by X-ray crystallography, solid-state and solution NMR, EPR spectroscopy and differential scanning calorimetry (DSC). The crystal structure, determined at 100 K, reveals that the complex occupies 422 site symmetry, which is compatible with the molecular symmetry of the container but not of the fullerene molecule, which has only 222 symmetry. The additional crystallographic symmetry leads to a complicated but discrete disorder, which could be resolved and modelled using advanced features of the existing refinement software. Solid-state NMR measurements at 184–333 K indicate that the thermal motion of C60 in this temperature range is fast but has different activation energies at different temperatures, which was attributed to a phase transition, which was confirmed by DSC. Intriguingly, the activation energy for reorientations of C60 in the solid state is very similar for the free and encaged molecules. Also, the rotational diffusion coefficients seem to be very similar or even slightly higher for the encaged fullerene compared to the free molecule. We also found that chemical shift anisotropy (CSA) is not the main relaxation mechanism for the 13C spins of C60 in the studied complex.

Beschreibung: A series of related acetylacetonate–carbonyl–rhodium compounds substituted by functionalized phosphines has been prepared in good to excellent yields by the reaction of [Rh(acac)(CO)2] (acac is acetylacetonate) with the corresponding allyl-, cyanomethyl- or cyanoethyl-substituted phosphines. All compounds were fully characterized by 31P, 1H, 13C NMR and IR spectroscopy. The X-ray structures of (acetylacetonato-κ2 O,O′)(tert-butylphosphanedicarbonitrile-κP)carbonylrhodium(I), [Rh(C5H7O2)(CO)(C8H13N2)] or [Rh(acac)(CO)(tBuP(CH2CN)2}] (2b), (acetylacetonato-κ2 O,O′)carbonyl[3-(diphenylphosphanyl)propanenitrile-κP]rhodium(I), [Rh(C5H7O2)(C15H14N)(CO)] or [Rh(acac)(CO){Ph2P(CH2CH2CN)}] (2h), and (acetylacetonato-κ2 O,O′)carbonyl[3-(di-tert-butylphosphanyl)propanenitrile-κP]rhodium(I), [Rh(C5H7O2)(C11H22N)(CO)] or [Rh(acac)(CO){tBu2P(CH2CH2CN)}] (2i), showed a square-planar geometry around the Rh atom with a significant trans influence over the acetylacetonate moiety, evidenced by long Rh—O bond lengths as expected for poor π-acceptor phosphines. The Rh—P distances displayed an inverse linear dependence with the coupling constants J P-Rh and the IR ν(C[triple-bond]O) bands, which accounts for the Rh—P electronic bonding feature (poor π-acceptors) of these complexes. A combined study from density functional theory (DFT) calculations and an evaluation of the intramolecular H...Rh contacts from X-ray diffraction data allowed a comparison of the conformational preferences of these complexes in the solid state versus the isolated compounds in the gas phase. For 2b, 2h and 2i, an energy-framework study evidenced that the crystal structures are mainly governed by dispersive energy. In fact, strong pairwise molecular dispersive interactions are responsible for the columnar arrangement observed in these complexes. A Hirshfeld surface analysis employing three-dimensional molecular surface contours and two-dimensional fingerprint plots indicated that the structures are stabilized by H...H, C...H, H...O, H...N and H...Rh intermolecular interactions.

Beschreibung: The synthesis and X-ray structure determination of the [Mn(CO)4{(C6H5)2P-S-C(Br2)-P(C6H5)2}]Br complex (1) are described. The C—Br...Br dihalogen bond present in 1 has been characterized by means of topological studies of the electron density. Both the quantum theory of atoms in molecules and the electron localization function approaches have been applied to several theoretically calculated wavefunctions as well as to an X-ray constrained wavefunction. In addition, a number of theoretical techniques, such as the source function, the reduced density gradient method and the interacting quantum atoms approach, among others, have been used to analyse the dihalogen bond as well as several intramolecular interactions of the type C—H...Br—C which have also been detected in 1. The results show clearly that while bonding in the latter interactions are dominated by electrostatic components, the former has a high degree of covalency.

Beschreibung: The synthesis and structures of three isoxazole-containing Schiff bases are reported, namely, (E)-2-{[(isoxazol-3-yl)imino]methyl}phenol, C10H8N2O2, (E)-2-{[(5-methylisoxazol-3-yl)imino]methyl}phenol, C11H10N2O2, and (E)-2,4-di-tert-butyl-6-{[(isoxazol-3-yl)imino]methyl}phenol, C18H24N2O2. All three structures contain an intramolecular O—H...N hydrogen bond, alongside weaker intermolecular C—H...N and C—H...O contacts. The C—O(H) and imine C=N bond lengths were consistent with structures existing in the enol rather than the keto form. Despite having dihedral angles

Beschreibung: Anion...π interactions are newly recognized weak supramolecular forces which are relevant to many types of electron-deficient aromatic substrates. Being less competitive with respect to conventional hydrogen bonding, anion...π interactions are only rarely considered as a crystal-structure-defining factor. Their significance dramatically increases for polyoxometalate (POM) species, which offer extended oxide surfaces for maintaining dense aromatic/inorganic stacks. The structures of tetrakis(caffeinium) μ12-silicato-tetracosa-μ2-oxido-dodecaoxidododecatungsten trihydrate, (C8H11N4O2)4[SiW12O40]·3H2O, (1), and tris(theobrominium) μ12-phosphato-tetracosa-μ2-oxido-dodecaoxidododecatungsten ethanol sesquisolvate, (C7H9N4O2)3[PW12O40]·1.5C2H5OH, (2), support the utility of anion...π interactions as a special kind of supramolecular synthon controlling the structures of ionic lattices. Both caffeinium [(HCaf)+ in (1)] and theobrominium cations [(HTbr)+ in (2)] reveal double stacking patterns at both axial sides of the aromatic frameworks, leading to the generation of anion...π...anion bridges. The latter provide the rare face-to-face linkage of the anions. In (1), every square face of the metal–oxide cuboctahedra accepts the interaction and the above bridges yield flat square nets, i.e. {(HCaf+)2[SiW12O40]4−} n . Two additional cations afford single stacks only and they terminate the connectivity. Salt (2) retains a two-dimensional (2D) motif of square nets, with anion...π...anion bridges involving two of the three (HTbr)+ cations. The remaining cations complete a fivefold anion...π environment of [PW12O40]3−, acting as terminal groups. This single anion...π interaction is influenced by the specific pairing of (HTbr)+ cations by double amide-to-amide hydrogen bonding. Nevertheless, invariable 2D patterns in (1) and (2) suggest the dominant role of anion...π interactions as the structure-governing factor, which is applicable to the construction of noncovalent linkages involving Keggin-type oxometalates.

Beschreibung: The generating sets of { b Z}^4 have been enumerated which consist of integral four-dimensional vectors with components −1, 0, 1 and allow Cayley graphs without edge intersections in a straight-edge embedding in a four-dimensional Euclidean space. Owing to computational restrictions the valency of enumerated graphs has been fixed to 10. Up to isomorphism 58 graphs have been found and characterized by coordination sequences, shortest cycles and automorphism groups. To compute automorphism groups, a novel strategy is introduced that is based on determining vertex stabilizers from the automorphism group of a sufficiently large finite ball cut out from an infinite graph. Six exceptional, rather `dense' graphs have been identified which are locally isomorphic to a five-dimensional cubic lattice within a ball of radius 10. They could be built by either interconnecting interpenetrated three- or four-dimensional cubic lattices and therefore necessarily contain Hopf links between quadrangular cycles. As a consequence, a local combinatorial isomorphism does not extend to a local isotopy.

Beschreibung: Threefold twinning in 1-{(R)-1-[(3-oxo-2-isoindolinoyl)methyl]-2-propenyl}-5-methyl-2,3-indolinedione, C21H16N2O4, has been reported recently [Trost et al. (2020). Org. Lett. 22, 2584–2589] but the twin characterization was not published. This twinning presents several interesting features. The crystal structure is monoclinic, but its lattice is metrically strongly pseudo-orthorhombic and underpins a strongly pseudo-hexagonal sublattice. Several possible twin laws are compatible with these metric specializations, among which the one found experimentally corresponds to a trichromatic point group. Twinning is by reticular pseudo-merohedry with twin index 2 and zero obliquity but a non-zero twin misfit. The twin lattice coincides with the pseudo-hexagonal sublattice of the individual domain, which justifies the adoption of the unconventional setting B21 of the space group.

Beschreibung: This work presents the results of research on a Co49Ni21Ga30 magnetic shape memory single crystal. Based on a literature review, it was identified that analyses of phase transformations have been limited to specific heating and cooling rates, which could lead to an incomplete description of the resulting phenomena. Differential scanning calorimetry (DSC) performed with different heating/cooling rates enabled the precise determination of enthalpy values, which deviate from literature values. Weak and previously unnoticed thermal phenomena at temperatures below 190 K were also observed. Their presence was confirmed by low-temperature in situ transmission electron microscopy (TEM). Through DSC measurements and TEM observations, a model of the discovered phenomenon was proposed, which may have an impact on a better understanding of the physics of magnetic shape memory materials.

Beschreibung: The experimental charge-density distribution in [Gd(H2O)9](CF3SO3)3 has been analysed and compared with the theoretical density functional theory calculations. Although the Gd—OH2 bonds are mainly ionic, a covalent contribution is detectable when inspecting both the topological parameters of these bonds and the natural bond orbital results. This contribution originates from small electron transfer from the lone pairs of oxygen atoms to empty 5d and 6s spin orbitals of Gd3+.

Beschreibung: MgCO3·MgCl2·7H2O is the only known neutral magnesium carbonate containing chloride ions at ambient conditions. According to the literature, only small and twinned crystals of this double salt could be synthesised in a concentrated solution of MgCl2. For the crystal structure solution, single-crystal diffraction was carried out at a synchrotron radiation source. The monoclinic crystal structure (space group Cc) exhibits double chains of MgO octahedra linked by corners, connected by carbonate units and water molecules. The chloride ions are positioned between these double chains parallel to the (100) plane. Dry MgCO3·MgCl2·7H2O decomposes in the air to chlorartinite, Mg2(OH)Cl(CO3)·nH2O (n = 2 or 3). This work includes an extensive characterization of the title compound by powder X-ray diffraction, thermal analysis, SEM and vibrational spectroscopy.

Beschreibung: Here, the first accurate study is presented of the room-temperature and 100 K structures of one of the first organic spin liquids, κ-(BEDT-TTF)2Ag2(CN)3. It is shown that the monoclinic structure determined previously is only the average one. It is shown that the exact structure presents triclinic symmetry with two non-equivalent dimers in the unit cell. But surprisingly this does not lead to a sizeable charge disproportionation between dimers. The difference from the analogue compound κ-(BEDT-TTF)2Cu2(CN)3 which also presents a spin liquid phase is discussed in detail. The data provided here show the importance of the anionic layer and in particular the transition metal position in the process of symmetry breaking. The possible impact of the symmetry breaking, albeit weak, on the spin-liquid mechanism and the influence of various disorders on the physical properties of this system is also discussed.

Beschreibung: The investigation of elemental composition, crystal structure and thermal behavior of vonsenite and hulsite from the Titovskoe boron deposit in Russia is reported. The structures of the borates are described in terms of cation-centered and oxocentred polyhedra. There are different sequences of double chains and layers consisting of oxocentred [OM 4] n + tetrahedra and [OM 5] n + tetragonal pyramids forming a framework. Elemental composition was determined by energy-dispersive X-ray spectroscopy (EDX). Oxidation states and coordination sites of iron and tin in the oxoborates are determined using Mössbauer spectroscopy and compared with EDX and X-ray diffraction data (XRD). According to results obtained from high-temperature Mössbauer spectroscopy, the Fe2+ to Fe3+ oxidation in vonsenite and hulsite occurs at approximately 500 and 600 K, respectively. According to the high-temperature XRD data, this process is accompanied by an assumed deformation of crystal structures and subsequent solid-phase decomposition to hematite and warwickite. It is seen as a monotonic decrease of volume thermal expansion coefficients with an increase in temperature. A partial magnetic ordering in hulsite is observed for the first time with T c ≃ 383 K. Near this temperature, an unusual change of thermal expansion coefficients is revealed. Vonsenite starts to melt at 1571 K and hulsite melts at 1504 K. Eigenvalues of thermal expansion tensor are calculated for the oxoborates as well as anisotropy of the expansion is described in comparison with their crystal structures.

Beschreibung: The crystal structure of new Mg9Ni6Ga14 and Mg3Ni2Ga compounds were investigated by single-crystal diffraction. Both structures can be described as three-core-shell cluster compounds. In the Mg6Ni9Ga14 structure, the [Ni6Ga6] icosahedron is encapsulated within the [Mg20] dodecahedron, which is again encapsulated within a [Ni18Ga42] fullerene-like truncated icosahedron, thus the three core–shell cluster [Ni6Ga6@Mg20@Ni18Ga42] results. In the Mg3Ni2Ga structure, the [Mg6] octahedron is encapsulated within the [Ni12Ga6] flattened icosahedron in vertices of which there are 12 nickel atoms, and six lateral edges are centered by gallium atoms, which in turn is encapsulated within a [Mg36] pseudo-rhombicuboctahedron with 12 additional atoms centering the lateral faces; thus for Mg3Ni2Ga the three-shell cluster is [Mg6@Ni12Ga6@Mg36].

Beschreibung: Nylon 5T is one of the bio-based nylons, its raw material 1,5-pentanediamine is derived from biomass resources and produced by biological methods. 1,5-pentanediamine-terephthalate (PDA-TPA) is the monomeric salt for nylon 5T polymerization, and its own product quality has a significant impact on the performance of nylon 5T. PDA-TPA was prepared by anti-solvent crystallization in this study. It exists in two solid forms, a monohydrate [form (I)] and an anhydrous phase [form (II)]. The transition temperature of the two phases was around 65°C in the given ethanol–water binary (7:1) mixture. The characterization of monohydrate and anhydrate phases regarding structures and stabilities was carefully carried out using powder X-ray diffraction, single crystal X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, hot-stage microscopy and Fourier transform infrared spectroscopy. The relationship between the molecular interactions of monohydrate and anhydrate phases under different packing architectures and their thermal behaviours was analysed and established. In addition, the relationships between the structures and thermal behaviours for the two solid forms were analysed and established. In addition, the effect of solvent on phase conversion, the relationships between the temperature and water activity, as well as the relative stability of monohydrate and anhydrate phases under different thermodynamic conditions, were investigated by solid–solid transformation and solvent-mediated transformation experiments. It was obvious that the transition temperature of monohydrate and anhydrate phases of PDA-TPA was significantly influenced by water activity, and the larger the value of water activity is, the higher is the transition temperature. These studies give insight into the transformation of nylon 5T monomer salt and contribute to the control of target crystal preparation.

Beschreibung: [Ni{2-H2NC(=O)C5H4N}2(H2O)2][Ni{2,6-(O2C)2C5H3N}2]·4.67H2O, a new complex salt containing a bis(2,6-dicarboxypyridine)nickel(II) anion and a bis(2-amidopyridine)diaquanickel(II) cation, was synthesized and characterized. The crystal is stabilized by an extensive network of hydrogen bonds. Alternate layers of anions and cations/water molecules parallel to (010) can be distinguished. Computational studies of the network packing of the title compound by high-level DFT-D/B3LYP calculations indicate stabilization of the networks with conventional and non-conventional intermolecular O—H...O, N—H...O and C—H...O hydrogen bonds along with π-stacking contacts. Due to the presence of water molecules and the importance of forming hydrogen bonds with the involvement of water clusters to the stability of the crystal packing, the importance and role of these water clusters, and the quantitative stability resulting from the formation of hydrogen bonds and possibly other noncovalent bonds such as π-stacking are examined. The binding energies obtained by DFT-D calculations for these contacts indicate that hydrogen bonds, especially O—H...O and N—H...O, control the construction of the crystalline packing. Additionally, the results of Bader's theory of AIM for these interactions agree reasonably well with the calculated energies.

Beschreibung: Tilings based on the cut-and-project method are key model systems for the description of aperiodic solids. Typically, quantities of interest in crystallography involve averaging over large patches, and are well defined only in the infinite-volume limit. In particular, this is the case for autocorrelation and diffraction measures. For cut-and-project systems, the averaging can conveniently be transferred to internal space, which means dealing with the corresponding windows. In this topical review, this is illustrated by the example of averaged shelling numbers for the Fibonacci tiling, and the standard approach to the diffraction for this example is recapitulated. Further, recent developments are discussed for cut-and-project structures with an inflation symmetry, which are based on an internal counterpart of the renormalization cocycle. Finally, a brief review is given of the notion of hyperuniformity, which has recently gained popularity, and its application to aperiodic structures.

Beschreibung: The famous Euler's rule for three-dimensional polyhedra, F − E + V = 2 (F, E and V are the numbers of faces, edges and vertices, respectively), when extended to many tested cases of space-filling polyhedra such as the asymmetric unit (ASU), takes the form Fn − En + Vn = 1, where Fn, En and Vn enumerate the corresponding elements, normalized by their multiplicity, i.e. by the number of times they are repeated by the space-group symmetry. This modified formula holds for the ASUs of all 230 space groups and 17 two-dimensional planar groups as specified in the International Tables for Crystallography, and for a number of tested Dirichlet domains, suggesting that it may have a general character. The modification of the formula stems from the fact that in a symmetrical space-filling arrangement the polyhedra (such as the ASU) have incomplete bounding elements (faces, edges, vertices), since they are shared (in various degrees) with the space-filling neighbors.

Beschreibung: The structure of calcium europium orthoborate, Ca3Eu2(BO3)4, was determined using high-resolution powder X-ray diffraction data collected at the ID22 beamline (ESRF) under ambient conditions, as well as at high temperature. Rietveld refinement allowed determination of the lattice constants and structural details, including the Ca/Eu ratios at the three cationic sites and their evolution with temperature. Clear thermal expansion anisotropy was found, and slope changes of lattice-constant dependencies on temperature were observed at 923 K. Above this temperature the changes in occupation of the Ca/Eu sites occur, exhibiting a tendency towards a more uniform Eu distribution over the three Ca/Eu sites. Possible structural origins of the observed thermal expansion anisotropy are discussed.

Beschreibung: The inner-crystal quantum electronic pressure was estimated for unstrained C6Cl6, C6Br6, and C6I6 crystals and for those under external compression simulated from 1 to 20 GPa. The changes in its distribution were analyzed for the main structural elements in considered crystals: for triangles of the typical halogen bonds assembled in Hal3-synthons, where Hal = Cl, Br, I; for Hal...Hal stacking interactions, as well as for covalent bonds. Under simulated external compression, the quantum electronic pressure in the intermolecular space reduces as the electron density increases, indicating spatial areas of relatively less crystal resistance to external compression. The most compliant C6Cl6 crystal shows the largest changes of quantum electronic pressure in the centre of Cl3-synthon while the deformation of rigid I3-synthon under external compression depends only on the features of I...I halogen bonds.

Beschreibung: In the title molecule, C20H24Br2N4, the imidazopyridine moiety is not planar as indicated by the dihedral angle of 2.0 (2)° between the constituent rings; the 4-dimethylaminophenyl ring is inclined to the mean plane of the imidazole ring by 27.4 (1)°. In the crystal, two sets of C—H...π(ring) interactions form stacks of molecules extending parallel to the a-axis direction. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (42.2%), H...C/C...H (23.1%) and H...Br/Br...H (22.3%) interactions. The optimized structure calculated using density functional theory (DFT) at the B3LYP/ 6–311 G(d,p) level is compared with the experimentally determined structure in the solid state. The calculated HOMO–LUMO energy gap is 2.3591 eV.

Beschreibung: In the title unsymmetrical tertiary amine, C24H33NO2, which arose from the ring-opening reaction of a dihydrobenzoxazine, two 2,4-dimethylphenol moieties are linked by a 6,6′-(cyclohexylazanediyl)-bis(methylene) bridge: the dihedral angle between the dimethylphenol rings is 72.45 (7)°. The cyclohexyl ring adopts a chair conformation with the exocyclic C—N bond in an equatorial orientation. One of the phenol OH groups forms an intramolecular O—H...N hydrogen bond, generating an S(6) ring, and a short intramolecular C—H...O contact is also present. In the crystal, O—H...O hydrogen bonds link the molecules into C(10) chains propagating along the [100] direction. The Hirshfeld surface analysis of the title compound confirms the presence of these intra- and intermolecular interactions. The corresponding fingerprint plots indicate that the most significant contacts in the crystal packing are H...H (76.4%), H...C/C...H (16.3%), and H...O/O...H (7.2%).

Beschreibung: The complete molecule of the title hydrazine carbodithioate derivative, C32H30N4O2S4, is generated by a crystallographic twofold axis that bisects the disulfide bond. The molecule is twisted about this bond with the C—S—S—C torsion angle of 90.70 (8)° indicating an orthogonal relationship between the symmetry-related halves of the molecule. The conformation about the imine bond [1.282 (2) Å] is E and there is limited delocalization of π-electron density over the CN2C residue as there is a twist about the N—N bond [C—N—N—C torsion angle = −166.57 (15)°]. An intramolecular hydroxyl-O—H...N(imine) hydrogen bond closes an S(6) loop. In the crystal, methylene-C—H...π(tolyl) contacts assemble molecules into a supramolecular layer propagating in the ab plane: the layers stack without directional interactions between them. The analysis of the calculated Hirshfeld surfaces confirm the importance of H...H contacts, which contribute 46.7% of all contacts followed by H...C/C...H contacts [25.5%] reflecting, in part, the C—H...π(tolyl) contacts. The calculation of the interaction energies confirm the importance of the dispersion term and the influence of the stabilizing H...H contacts in the inter-layer region.

Beschreibung: In the title compound, C18H19Cl2N3, the planes of the benzene rings subtend a dihedral angle of 77.07 (10)°. In the crystal, molecules are associated into inversion dimers via short Cl...Cl contacts [3.3763 (9) Å]. A Hirshfeld surface analysis indicates that the most important contact percentages for the different types of interactions are H...H (43.9%), Cl...H/H...Cl (22.9%), C...H/H...C (20.8%) and N...H/H...N (8.0%).

Beschreibung: The title morpholinochlorin, C46H16F20N4O3, was crystallized from hexane/methylene chloride as its 0.44 methylene chloride solvate, C46H16F20N4O3·0.44CH2Cl2. The morpholinochlorin was synthesized by stepwise oxygen insertion into a porphyrin using a `breaking and mending strategy': NaIO4-induced diol cleavage of the corresponding 2,3-dihydroxychlorin with in situ methanol-induced, acid-catalyzed intramolecular ring closure of the intermediate secochlorins bisaldehyde. Formally, one of the pyrrolic building blocks was thus replaced by a 2,3-dimethoxymorpholine moiety. Like other morpholinochlorins, the macrocycle of the title compound adopts a ruffled conformation, and the modulation of the porphyrinic π-system chromophore induces a red-shift of its optical spectrum compared to its corresponding chlorin analog. Packing in the crystal is governed by interactions involving the fluorine atoms of the pentafluorophenyl substituents, dominated by C—H...F interactions, and augmented by short fluorine...fluorine contacts, C—F...π interactions, and one severely slipped π-stacking interaction between two pentafluorophenyl rings. The solvate methylene chloride molecule is disordered over two independent positions around an inversion center with occupancies of two × 0.241 (5) and two × 0.199 (4), for a total site occupancy of 88%.

Beschreibung: The title compound, C15H15NO, is an enantiopure small molecule, which has been synthesized many times, although its crystal structure was never determined. By recrystallization from a variety of solvent mixtures (pure acetonitrile, ethanol–water, toluene–ethanol, THF–methanol), we obtained three unsolvated polymorphs, in space groups P21 and P212121. Form I is obtained from acetonitrile, without admixture of other forms, whereas forms II and III are obtained simultaneously by concomitant crystallizations from alcohol-based solvent mixtures. All forms share the same supramolecular structure, based on infinite C 1 1(4) chain motifs formed by N—H...O intermolecular hydrogen bonds, as usual for non-sterically hindered amides. However, a conformational modification of the molecular structure, related to the rotation of the phenyl rings, alters the packing of the chains in the crystal structures. The orientation of the chain axis is perpendicular and parallel to the crystallographic twofold screw axis of space group P21 in forms I and II, respectively. As for form III, the asymmetric unit contains two independent molecules forming parallel chains in space group P212121, and the crystal structure combines features of monoclinic forms I and II.

Beschreibung: The syntheses and crystal structures for the compounds tetra-μ-aqua-tetrakis{2-[azanidylene(oxido)methyl]phenolato}tetrakis(μ2-3-hydroxybenzoato)dysprosium(III)tetramanganese(III)sodium(I) N,N-dimethylacetamide decasolvate, [DyMn4Na(C7H5O3)4(C7H4NO2)4(H2O)4]·10C4H9NO or [DyIIINa(4-OHben)4{12-MCMn(III)N(shi)-4}(H2O)4]·10DMA, 1, and tetra-μ-aqua-tetrakis{2-[azanidylene(oxido)methyl]phenolato}tetrakis(μ2-3-hydroxybenzoato)dysprosium(III)tetramanganese(III)sodium(I) N,N-dimethylformamide tetrasolvate, [DyMn4Na(C7H5O3)4(C7H4NO2)4(H2O)4]·4C3H7NO or [DyIIINa(3-OHben)4{12-MCMn(III)N(shi)-4}(H2O)4]·4DMF, 2, and where MC is metallacrown, shi3− is salicylhydroximate, 3-OHben is 3-hydroxybenzoate, DMA is N,N-dimethylacetamide, 4-OHben is 4-hydroxybenzoate, and DMF is N,N-dimethylformamide, are reported. For both 1 and 2, the macrocyclic metallacrown consists of an [MnIII—N—O] ring repeat unit, and the domed metallacrown captures two ions in the central cavity: a DyIII ion on the convex side of the metallacrown and an Na+ ion the concave side. The MnIII ions are six-coordinate with an elongated tetragonally distorted octahedral geometry. Both the DyIII and Na+ ions are eight-coordinate. The DyIII ions possess a square-antiprismatic geometry, while the Na+ ions have a distorted biaugmented trigonal–prismatic geometry. Four 3-hydroxybenzoate or 4-hydroxybenzoate ligands bridge each MnIII ion to the central DyIII ion. For 1, whole-molecule disorder is observed for the main molecule, excluding only the DyIII and Na+ ions, and the occupancy ratio refined to 0.8018 (14):0.1982 (14). Three DMA molecules were refined as disordered with two in general positions by an approximate 180° rotation and the third disordered twice by general disorder as well as by an exact 180° rotation about a twofold axis that bisects it. The occupancy ratios refined to 0.496 (8):0.504 (8), 0.608 (9):0.392 (9), and 2×0.275 (7):2×0.225 (7), respectively. For 2, segments of the metallacrown are disordered including the DyIII ion, one of the Mn ions, two of the Mn-bound 4-hydroxybenzoate ligands, the Mn-bridging salicylhydroximate ligand, and portions of the remaining three shi3− ligands. The occupancy ratio for the metallacrown disorder refined to 0.849 (9):0.151 (9). Two DMF solvent molecules are also disordered, each over two orientations. The disorder ratios refined to 0.64 (3):0.36 (3) and to 0.51 (2):0.49 (2), respectively. For 2, the crystal under investigation was refined as a non-merohedric twin by a 90° rotation around the real a axis [twin ratio 0.9182 (8):0.0818 (8)].

Beschreibung: The title compounds, 2-(ferrocenylcarbonyl)benzoic acid, [Fe(C5H5)(C13H9O3)], 1, and 3-ferrocenylphthalide [systematic name: 3-ferrocenyl-2-benzofuran-1(3H)-one], [Fe(C5H5)(C13H9O2)], 2, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The crystal structure of compound 1 was solved recently at room temperature [Qin, Y. (2019). CSD Communication (CCDC deposition number 1912662). CCDC, Cambridge, England]. Here we report a redetermination of its crystal structure at 90 K with improved precision by a factor of about three. The molecular structures of both compounds exhibit a typical sandwich structure. In the crystal packing of compound 1, each molecule engages in intermolecular hydrogen bonding, forming a centrosymmetric dimer with graph-set notation R 2 2 (8) and an O...O distance of 2.6073 (15) Å. There are weak C—H...O and C—H...π interactions in the crystal packing of compound 2. The phthalide moiety in 2 is oriented roughly perpendicular to the ferrocene backbone, with a dihedral angle of 77.4 (2)°.

Beschreibung: The structures of two hydroxy-thiophenone derivatives related to the antibiotic thiolactomycin are presented. These are the racemic 3-hydroxy-2,4-dimethyl-2H-thiophen-5-one, C6H8O2S, and 3-hydroxy-4-methyl-2H-thiophen-5-one, C5H6O2S. The main structural feature of both compounds is C(6) hydrogen-bonded chains formed between the OH and C=O groups. In achiral C5H6O2S, these chains propagate only by translation, corresponding to x + 1, y, z + 1. However, in contrast, for racemic C6H8O2S the hydrogen-bonded chains propagate through a −x + {3over 2}, y + {1over 2}, z operation, giving chains lying parallel to the crystallographic b-axis direction that are composed of alternate R and S enantiomers. The crystals of 3-hydroxy-4-methyl-2H-thiophen-5-one were found to be twinned by a 180° rotation about the reciprocal 001 direction. In the final refinement the twin ratio refined to 0.568 (2):0.432 (2).

Beschreibung: The crystal structures of a new polymorph of dipotassium hydrogen citrate, 2K+·HC6H5O7 2−, and potassium rubidium hydrogen citrate, K+·Rb+·HC6H5O7 2−, have been solved and refined using laboratory powder X-ray diffraction and optimized using density functional techniques. In the new polymorph of the dipotassium salt, KO7 and KO8 coordination polyhedra share corners and edges to form a three-dimensional framework with channels parallel to the a axis and [111]. The hydrophobic methylene groups face each other in the channels. The un-ionized carboxylic acid group forms a strong charge-assisted hydrogen bond to the central ionized carboxylate group. The hydroxy group forms an intermolecular hydrogen bond to a different central carboxylate group. In the potassium rubidium salt, the K+ and Rb+ cations are disordered over two sites, in approximately 0.72:0.28 and 0.28:0.72 ratios. KO8 and RbO9 coordination polyhedra share corners and edges to form a three-dimensional framework with channels parallel to the a axis. The un-ionized carboxylic acid group forms a strong charge-assisted hydrogen bond to an ionized carboxylate group. The hydroxy group forms an intermolecular hydrogen bond to the central carboxylate group. Density functional theory (DFT) calculations on the ordered cation structures suggest that interchange of K+ and Rb+ at the two cation sites changes the energy insignificantly.

Beschreibung: A mathematical description of crystal structure is proposed consisting of two parts: the underlying translational periodicity and the distinct atomic positions up to the symmetry operations in the unit cell, consistent with the International Tables for Crystallography. By the Cauchy–Born hypothesis, such a description can be integrated with the theory of continuum mechanics to calculate a derived crystal structure produced by solid–solid phase transformation. In addition, the expressions for the orientation relationship between the parent lattice and the derived lattice are generalized. The derived structure rationalizes the lattice parameters and the general equivalent atomic positions that assist the indexing process of X-ray diffraction analysis for low-symmetry martensitic materials undergoing phase transformation. The analysis is demonstrated in a CuAlMn shape memory alloy. From its austenite phase (L21 face-centered cubic structure), it is identified that the derived martensitic structure has orthorhombic symmetry Pmmn with the derived lattice parameters a d = 4.36491, b d = 5.40865 and c d = 4.2402 Å, by which the complicated X-ray Laue diffraction pattern can be well indexed, and the orientation relationship can be verified.

Beschreibung: An extension is proposed of the Shannon entropy-based structural complexity measure introduced by Krivovichev, taking into account the geometric coordinational degrees of freedom a crystal structure has. This allows a discrimination to be made between crystal structures which share the same number of atoms in their reduced cells, yet differ in the number of their free parameters with respect to their fractional atomic coordinates. The strong additivity property of the Shannon entropy is used to shed light on the complexity measure of Krivovichev and how it gains complexity contributions due to single Wyckoff positions. Using the same property allows for combining the proposed coordinational complexity measure with Krivovichev's combinatorial one to give a unique quantitative descriptor of a crystal structure's configurational complexity. An additional contribution of chemical degrees of freedom is discussed, yielding an even more refined scheme of complexity measures which can be obtained from a crystal structure's description: the six C's of complexity.

Beschreibung: The asymmetric unit of the title salt, C17H21N4S+·C7H5O4 −·C3H7OH, consists of an olanzapinium cation, an independent 2,5-dihydroxybenzoate anion and a solvent isopropyl alcohol molecule. The central seven-membered heterocycle is in a boat conformation, while the piperazine ring displays a distorted chair conformation. The dihedral angle between the benzene and thiene rings flanking the diazepine ring is 52.58 (19)°. In the crystal, the anions and cations are connected by N—H...O and O—H...O hydrogen bonds, forming a three-dimensional network.

Beschreibung: Carbonic anhydrases (CAs) are a well characterized family of metalloenzymes that are highly efficient in facilitating the interconversion between carbon dioxide and bicarbonate. Recently, CA activity has been associated with the LCIB (limiting CO2-inducible protein B) protein family, which has been an interesting target in aquatic photosynthetic microorganisms. To gain further insight into the catalytic mechanism of this new group of CAs, the X-ray structure of a highly active LCIB homolog (PtLCIB3) from the diatom Phaeodactylum tricornutum was determined. The CA activities of PtLCIB3, its paralog PtLCIB4 and a variety of their mutants were also measured. It was discovered that PtLCIB3 has a classic β-CA fold and its overall structure is highly similar to that of its homolog PtLCIB4. Subtle structural alterations between PtLCIB3 and PtLCIB4 indicate that an alternative proton-shuttle cavity could perhaps be one reason for their remarkable difference in CA activity. A potential alternative proton-shuttle route in the LCIB protein family is suggested based on these results.

Beschreibung: GLIC is a bacterial homologue of the pentameric ligand-gated ion channels (pLGICs) that mediate the fast chemical neurotransmission of nerve signalling in eukaryotes. Because the activation and allosteric modulation features are conserved among prokaryotic and eukaryotic pLGICs, GLIC is commonly used as a model to study the allosteric transition and structural pharmacology of pLGICs. It has previously been shown that GLIC is inhibited by some carboxylic acid derivatives. Here, experimental evidence for carboxylate binding to GLIC is provided by solving its X-ray structures with a series of monocarboxylate and dicarboxylate derivatives, and two carboxylate-binding sites are described: (i) the `intersubunit' site that partially overlaps the canonical pLGIC orthosteric site and (ii) the `intrasubunit' vestibular site, which is only occupied by a subset of the described derivatives. While the intersubunit site is widely conserved in all pLGICs, the intrasubunit site is only conserved in cationic eukaryotic pLGICs. This study sheds light on the importance of these two extracellular modulation sites as potential drug targets in pLGICs.

Beschreibung: Flavin-dependent halogenases regioselectively introduce halide substituents into electron-rich substrates under mild reaction conditions. For the enzyme Xcc4156 from Xanthomonas campestris, the structure of a complex with the cofactor flavin adenine dinucleotide (FAD) and a bromide ion would be of particular interest as this enzyme exclusively brominates model substrates in vitro. Apo Xcc4156 crystals diffracted to 1.6 Å resolution. The structure revealed an open substrate-binding site lacking the loop regions that close off the active site and contribute to substrate binding in tryptophan halogenases. Therefore, Xcc4156 might accept larger substrates, possibly even peptides. Soaking of apo Xcc4156 crystals with FAD led to crumbling of the intergrown crystals. Around half of the crystals soaked with FAD did not diffract, while in the others there was no electron density for FAD. The FAD-binding loop, which changes its conformation between the apo and the FAD-bound form in related enzymes, is involved in a crystal contact in the apo Xcc4156 crystals. The conformational change that is predicted to occur upon FAD binding would disrupt this crystal contact, providing a likely explanation for the destruction of the apo crystals in the presence of FAD. Soaking with only bromide did not result in bromide bound to the catalytic halide-binding site. Simultaneous soaking with FAD and bromide damaged the crystals more severely than soaking with only FAD. Together, these latter two observations suggest that FAD and bromide bind to Xcc4156 with positive cooperativity. Thus, apo Xcc4156 crystals provide functional insight into FAD and bromide binding, even though neither the cofactor nor the halide is visible in the structure.