engleski

Coordination modes of 3-hydroxypicolinic acid (OH-picH): synthesis and characterization of cadmium(II) complexes. Crystal and molecular structures of [CdX(OH-pic)(OH-picH)(H_2O]_2 X = Cl- , Br-

Two complexes of 3-hydroxypicolinic acid and cadmium(II) chloride and bromide, namely di-mi-halo-(aqua-(3-hydroxypyridine-2-carboxylato-N, O)(3-hydroxypyridinium-2-carboxylato-O)cadmium(II)), halo = Cl (1), Br (2) have been prepared and characterized by spectroscopic, thermal and X-ray crystallographic methods. The IR and thermal data correlate with the structures of the complexes in solid state. The vibration bands of diagnostic value are compared to the values of the free acid. The complexes 1 and 2 are isostructural. The molecular structures of complexes 1 and 2 comprise centrosymmetrical dimers formed via di-mi-halide bridge. The distorted octahedral cadmium coordination environment contains two halide atoms, one water molecule and two 3-OH-pic ligands, one bonded to the cadmium ion in a monodentate mode through carboxylate O atom and the other in the bidentate N, O-chelated mode forming five-membered chelate ring. Extensive network of the O-H...O and N-H...O hydrogen bonds are found. From 1H and 13C NMR measurements was determined that in dimethylformamide solution complexes 1 and 2 don't exist. Cd(OH-pic)2 is the only compound that was identified instead.

cadmium complexes; coordination modes of 3-hydroxypyridine-2-carboxylic acid; IR; NMR spectroscopy; X-ray diffraction; TGA/DTA analysis

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