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  • 1
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 407-411 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The sodium salt of a complex anion formed between gadolinium(III) and three variously deprotonated chelidamic acid (4-hydroxypyridine-2,6-dicarboxylic acid) ligand moieties, assigned as Na5[Gd(C7H2NO5)2(C7H3NO5)]·16H2O, i.e. pentasodium (4-hydroxypyridine-2,6-dicarboxylate)bis(4-oxidopyridine-2,6-dicarboxylate)gadolinium(III) hexadecahydrate, forms as colourless monoclinic crystals upon vapour diffusion of ethanol into its aqueous solution. The ligand moieties, assigned as two trianionic and one dianionic chelidamate species, are all tridentate in the complex anion of tricapped trigonal prismatic donor-atom geometry. The geometry of the ligands and that of the primary coordination sphere is very similar to that of the analogous anionic tris(ligand)–rare earth complexes of the pyridine-2,6-dicarboxylate (dipicolinate) dianion.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 448-450 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Chelidamic acid, 4-hydroxypyridine-2,6-dicarboxylic acid, is found to be zwitterionic in its solid monohydrate form, C7H5NO5·H2O, with the aryloxide and one carboxylate group remaining protonated, but the other carboxylate group losing its proton to the pyridine N atom. In this, it is unlike its parent, dipicolinic acid (pyridine-2,6-dicarboxylic acid), which also crystallizes as a monohydrate, but one in which the acidic H atoms remain bound to the carboxylate groups. In both structures, the water molecule is a component of an extended hydrogen-bonded network.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-1948
    Keywords: Thiacalixarene ; Trimetallic sandwich ; Cobalt ; Zinc ; Divergent receptors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction between deprotonated p-tert-butyltetrathiacalix[4]arene and CoII or ZnII under strictly defined conditions leads to the formation of sandwich species in which a trimetallic unit is held between two opposed, divergently oriented, staggered O- and S-bound calixarene ligands in the cone conformation. Despite the isomorphous nature of the crystalline compounds, there is a subtle difference in the coordination of CoII and ZnII, presumably related to the differences in metal radius and electron configuration combined with structural restrictions imposed by the calixarene framework, in that whereas all three Co atoms may be considered six-coordinate (and approximately octahedral), only two of the Zn atoms appear so, the third being five-coordinate and more nearly trigonal bipyramidal in its coordination geometry.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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