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Title
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Crystal structures of zinc(II) complexes with beta-hydroxypyridinecarboxylate ligands : examples of structure-directing effects used in inorganic crystal engineering
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Author
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Abstract
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| The coordination properties of four hydroxypyridinecarboxylates, designed for the treatment of iron-overloading conditions as bidentate O,O'-donor ligands, have been studied with ZIP in the solid state. The coordination compounds [Zn(Al)(2)(H2O)(2)] (1), [Zn(A2)(2)(H2O)] (2), [Zn(A3)(2)(H2O)]center dot 2H(2)O (3) and [Zn-2(B1)(4)(H2O)(2)]center dot 4H(2)O (4), where the ligands are 1-methyl-4-oxidopyridinium-3-carboxylate (A1, C7H6NO3), 1,6-dimethyl-4-oxidopyridinium-3-carboxylate (A2, C8H8NO3), 1,5-dimethyl-4-oxido-pyridinium-3-carboxylate (A3, C8H8NO3) and 1-methyl-3-oxidopyridinium-4-carboxylate (B1, C7H6NO3), have been synthesized and analysed by single-crystal X-ray diffraction. The ligands were chosen to probe (i) the electronic effects of inverting the positions of the O-atom donor groups (i.e. A1 versus B1) and (ii) the electronic and steric effects of the addition of a second methyl group in different positions on the pyridine ring. Two axially coordinated water molecules resulting in a six-coordinated symmetrical octahedron complement the bis-ligand complex of A1. Ligands A2 and A3 form five-coordinated trigonal bipyramidal complexes with one additional water molecule in the coordination sphere, which is a rarely reported geometry for Zn-II complexes. Ligand B1 shows a dimeric structure, where the two Zn2+ dications have slightly distorted octahedral geometry and the pyridinolate O atom of the neighbouring complex bridges them. The coordination spheres of the Zn2+ dications and the supramolecular structures are discussed in detail. The packing arrangements of 1-3 are similar, having alternating hydrophilic and hydrophobic layers, however the similarity is broken in 4. The obtained coordination geometries are compared with their previously determined Cu-II analogues. The study of the individual complexes is complemented with a comprehensive analysis of Zn-II complexes with oxygen donor ligands with data from the Cambridge Structural Database. |
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Language
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English
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Source (journal)
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Acta Crystallographica. Section B: Structural Science, Crystal Engineering and Materials (Online). - Oxford
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Publication
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Oxford
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Wiley-Blackwell
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2021
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ISSN
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2052-5206
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DOI
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10.1107/S2052520621000299
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Volume/pages
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77
:2
(2021)
, p. 193-204
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ISI
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000640218900002
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Pubmed ID
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33843726
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Full text (Publisher's DOI)
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Full text (open access)
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