Synthesis, characterization, and biological evaluation of Cu(II) complexes with the proton transfer salt of 2,6-pyridinedicarboxylic acid and 2-amino-4-methylpyridine

Abstract

A proton transfer compound, (Hamp)(+)(Hdipic)(-)center dot 1.5H(2)O (1), and Cu(II) complexes, [Cu(dipic)(amp)(H2O)]center dot[Cu(dipic)(amp)]center dot H2O center dot CH3COOH (2) and [Cu(dipic)(amp)Cu(dipic) (amp)(H2O)Cu(dipic)(amp)(H2O)]center dot 3H(2)O (3), have been synthesized from 2,6-pyridinedicarboxylic acid (H(2)dipic) and 2-amino-4-methylpyridine (amp). They have been characterized by elemental, spectral (H-1-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 five-coordinate, 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 H(2)dipic, at similar concentrations on preventing bacterial growth for both organisms.