Synthesis, crystal structure, spectroscopic and biological properties of mixed ligand complexes of zinc(II) valproate with 1,10-phenanthroline and 2-aminomethylpyridine

摘要

Mononuclear zinc(II) complexes with mixed ligands formulating [Zn(valp)_2(1,10-phen)H_2O] (2), and [Zn(valp)(2-picam) _2](valp) (3) (valp = valproate, phen = 1,10-phenanthroline, 2-picam = 2-aminomethylpyridine (2-picolylamine)) have been synthesized and characterized using IR, ~1H NMR, ~(13)C{~1H} NMR and UV-Vis spectroscopic techniques, as well as single-crystal X-ray diffraction. Zn(II) cation in 2 exhibits a distorted octahedral environment resulting from one bidentate phen ligand, one valproate ligand with asymmetric chelating mode, and another one with monodentate mode and a molecule of water. Complex 3 has two bidentate 2-ampic ligands and two valproate ligands. Only one of the carboxylate ligands was bonded to Zn(II) in a monodentate mode. The second valproate ligand acted as a counter ion and was bonded to the NH_2 groups of 2-picam through hydrogen bonding. The Zn(II) cation in 3 has a distorted trigonal bipyramidal arrangement. The complexes were also evaluated for their anti-bacterial activity using in vitro agar diffusion method. Three Gram-positive (Micrococcus luteus, Staphylococcus aureus, and Bacillus subtilis) and three Gram-negative (Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis) species of bacteria were used for testing anti-bacterial activities. Complex 2 showed considerable activity against all tested microorganisms. The effect of complexation on the anti-bacterial activity of the parent ligand of 2 was also investigated. The anti-bacterial activity of 1,10-phen against both Gram-positive and Gram-negative bacteria was reduced upon complexation with zinc valproate. Complex 3 showed weak inhibition activity against S. aureus, B. subtilis, E. coli and K. pneumoniae.