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  • 1
    ISSN: 1573-1111
    Keywords: anionic substrates ; molecular recognition ; cryptates ; crystal structures ; H-bonds ; intercalation ; inclusion complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular recognition of flat substrates requires the design of receptor molecules containing complementary flat units. If two such units are incorporated into a macrocyclic framework, a face to face inclusion of a planar substrate may take place, leading to an intercalative supramolecular structure. The water-soluble macrocyclic bis-intercaland receptor 1.4H+, containing two naphthalene subunits, linked by two positively charged oxy-bis- ethylamine binding sites, is able to bind strongly flat organic anions. The crystal structures of the terephthalate 2 and isophthalate 3 inclusion complexes are reported here. Complex 2, triclinic, P-1(N°), a = 7.717(3), b = 10.625(6), c = 16.238(9) Å, α = 99.00(7), β = 99.70(6), γ = 109.46(4)°, Z = 1. Complex 3, triclinic, P1 (N°1), a = 7.513(10), b = 10.640(9), c = 16.164(10) Å, α = 98.81(5), β = 99.77(10), γ = 109.36(12)°, Z = 1. Comparison of the environment (water molecules, anions and macrocycle) in the two X-ray structures highlights the formation of a similar organized assembly with the two different substrates.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nanoparticle research 1 (1999), S. 7-7 
    ISSN: 1572-896X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1421-1428 
    ISSN: 1434-1948
    Keywords: Grid complexes ; Self-assembly ; Co ; Zn ; Coordination chemistry ; Bis(tridentate) ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tretrametallic [2 × 2] grid-type complexes 1-4 are formed by self-assembly of the bis(tridentate) ligands 5 and 6 with ZnII and CoII cations. They have been characterized by spectroscopic studies in solution as well as by crystal structure determination. The substituents in the central pyrimidine ring play an important role in terms of geometry and physical properties of the complexes. They induce an orthogonal orientation of the ligand in the complexes which is critical for the formation of ordered monolayers and extended self-organized arrays of grids. The physical properties of the complexes such as metal-metal interaction and π-π* stacking between the ligands may be modulated by changing these substituents.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1409-1414 
    ISSN: 1434-1948
    Keywords: Ruthenium complexes ; Luminescence ; Bridging ligands ; Terpyridine ligands ; Polynuclear metal complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absorption spectra and the luminescence properties of three dinuclear RuII complexes and one trinuclear RuII complex have been investigated. All the complexes have rack-type structures. The dinuclear complexes 1, 2, and 3 incorporate a bis-tridentate bridging ligand made up of a pyrimidine and four pyridine moieties, as well as two 2,2′:6′,2′-terpyridyl (tpy) ligands. The trinuclear complex 4 incorporates a tris-tridentate bridging ligand made up of two pyrimidine and five pyridine moieties, as well as three tpy ligands. The absorption spectra of the complexes show a large number of ligand-centered (LC) and metal-to-ligand charge-transfer (MLCT) bands. All the complexes exhibit emission from a triplet MLCT state, with maxima in the spectral range 840-950 nm (lifetimes between 40 and 80 ns) at 298 K in fluid solution, and in the spectral range 760-810 nm (lifetimes between 2 and 3 μs) at 77 K in rigid matrices. A fine tuning of the absorption and luminescence properties of complexes 1-3can be achieved by changing the substituents on the pyrimidine ring of the bridging ligand. Efficient energy transfer within the rack structure 4 occurs from the (upper-lying) central metal-based chromophore to the (lower-lying) peripheral ones.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1415-1420 
    ISSN: 1434-1948
    Keywords: Combinatorial chemistry ; Molecular recognition ; Functionalized bipyridine metal complexes ; Janus molecules ; Hydrogen bonding ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The functionalized ligands 1 and 2 bearing hydrogen-bonding recognition groups have been synthesized. Their assembly by metal ions such as CuI and PdII having different coordination geometries generates different receptor architectures for the binding of suitable substrates. Addition of the complementary bis(imide) Janus molecules (4-7) to [1a, 2a, CuTf] or to [1b, 2b, Pd(BF4)2] mixtures leads to a moderate selective increase of the fraction of the [(1a)2Cu]+ or [(1b)2Pd]2+ complex depending on the Janus substrate used. Largest enhancements are observed for those Janus substrates that may be expected to display highest geometrical complementarity with the two complexes. These results represent a process directed by target binding based on dynamic combinatorial chemistry.
    Additional Material: 5 Ill.
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  • 6
    ISSN: 1434-1948
    Keywords: Self-assembly ; Tetranuclear CuII complex ; [2 × 2] grid-type complex ; Crystal structure ; Magnetic properties ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ditopic ligand 3 has been synthesized. In its deprotonated form, it reacts with copper(II) ions to form a tetranuclear complex 1 of the [2 × 2] CuII4 grid type, the structure of which has been confirmed by X-ray crystallography. Magnetic studies of complex 1 indicate a very weak antiferromagnetic coupling between the phenoxo-bridged CuII ions.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2359-2366 
    ISSN: 1434-193X
    Keywords: Photochromism ; Diarylethenes ; Molecular devices ; Proton switches ; Merocyanines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unsymmetrical dithienylethene photochrome 1a exhibits proton-gated photochromic properties as well as novel chemical reactivity. The dimethoxylated derivative 9a represents a light-triggered proton switch whose dissociation constant is increased by a factor of 16 upon photochemical cyclization to 9b. Such compounds are of potential interest for multiplexing photochemical systems.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 1434-193X
    Keywords: Dynamic combinatorial chemistry ; Molecular recognition ; Hydrogen bonding ; Hydrazone isomerization ; Barbiturate receptor ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The selection of the receptor presenting the strongest affinity for a barbiturate substrate from a dynamic combinatorial library of constituents differing in structure and conformation/configuration is described. The gradual addition of the barbiturate to an equilibrating mixture of hydrazone isomers leads to the quantitative shift towards a single species, 3, which presents highest complementarity to the substrate and yields the supramolecular entity 3:4.
    Additional Material: 2 Ill.
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  • 9
    ISSN: 1434-193X
    Keywords: Cyclo-bis-intercaland ; Acridine units ; cis/trans-Azobenzene dicarboxylic acids ; Inclusion compounds ; X-ray structure ; Molecular recognition ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The water soluble acyclic 1 and macrocyclic 2 receptor molecules, based on acridine units, form 1:1 complexes with the cis- or trans-2,2′ and 3,3′-azobenzene dicarboxylate substrates. The stability constants of these complexes, determined by 1H NMR spectroscopy, cover a wide range from 30 to 105M-1, thus displaying very pronounced structure selectivity with respect to both substitution pattern and cis, transconfiguration. The complexes of the cyclo-bis-intercaland receptor 2 are two or three orders of magnitude more stable than those of 1. The inclusion complex of cyclo-bis-intercaland 2 with trans-3,3′- azobenzene dicarboxylate has been isolated and its structure has been determined by X-ray crystallography using synchrotron radiation, confirming the intercalation of the substrate between the acridine residues in the species formed.
    Additional Material: 3 Ill.
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  • 10
    Publication Date: 1999-01-01
    Print ISSN: 0040-4039
    Electronic ISSN: 1873-3581
    Topics: Chemistry and Pharmacology
    Published by Elsevier
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