Synthesis, Characterization, and Biological Evaluation of Cu(II) Complexes with the Proton Transfer Salt of 2,6-Pyridinedicarboxylic Acid and 2-Aminopyridine Derivatives

Abstract

A proton transfer compound, (Hamp)+(Hdipic)- 1.5H<inf>2</inf>O (1), and Cu(II) complexes, Cu(dipic)(amp)(H<inf>2</inf>O)] . [Cu(dipic)(amp)] . H<inf>2</inf>O.CH<inf>3</inf>COOH (2) and [Cu(dipic)(amp)Cu(dipic) (amp)(H<inf>2</inf>O)Cu(dipic)(amp)(H<inf>2</inf>O)] .3H<inf>2</inf>O (3), have been synthesized from 2,6-pyridinedicarboxylic acid (H<inf>2</inf>dipic) and 2-amino-4-methylpyridine (amp). They have been characterized by elemental, spectral (1H-NMR, IR, and UV-Vis), and thermal analyses. In addition, magnetic measurements and single crystal X-ray diffraction have been applied to 2 and 3. The crystal structure of 2 consists of two independent and different cationic sites with Cu2+ ions. Cu1 is four-coordinate in a distorted square planar geometry and Cu2 is five-coordinate in a distorted square pyramid. Compound 3 has three independent and different cationic sites of Cu2+ ions. Cu1 is four-coordinate in a distorted square planar geometry and Cu2 and Cu3 have fivecoordinate, distorted square-pyramidal sites. Inhibitory effects of 1, 2, and 3 have been studied and compared with starting compounds (amp and H2dipic) on bacterial growth of Staphylococcus aureus and Escherichia coli cultures. Compounds 2 and 3 prevent bacterial growth although 1 has no effect. Compounds 2 and 3 are more effective than amp and H2dipic, at similar concentrations on preventing bacterial growth for both organisms. © 2011 Taylor & Francis.