Synthesis, spectral and magnetic properties and crystal structures of copper(II) pyridinecarboxylates as potential antimicrobial agents

Synthesis and characterization of six new complexes [Cu[2,6-(MeO)(2)nic)(2)(H2O)](2) (1), [Cu{2,6-(MeO)(2)nic)(2)(H2O)](2)center dot 3DMF (2), where 2,6-(MeO)(2)nic is 2,6-dimethoxynicotinate and DMF is N,N-dimethylformamide, [Cu(3-pyacr)(2)(H2O)(2)](n) (3), where 3-pyacr is trans-3-(3-pyridyl)acrylate, [Cu(en)(2)(H2O)(2)]X-2, where X is 2,6-(MeO)(2)nic (4) or 3-pyacr (5) and en is ethylenediamine, and [Cu(3-pyacr)(2)(dien)([mu-H2O)(0.5)](2) center dot 7H(2)O (6), where then is diethylenetriamine are reported. The characterizations were based on elemental analysis, infrared, electronic and EPR spectra, and magnetic measurements over a temperature range of 1.8-300 K. Crystal structures of complexes 2, 4 and 6 have been determined by X-ray single crystal structure analysis. The available evidence supports dimeric structure of the acetate type for 1 and 2. Crystal structure of polymeric complex 3 has been determined from X-ray powder diffraction data. The 3-pyacr anions in pairs form bridges between two octahedrally surrounded copper(II) atoms in such a way that one 3-pyacr is coordinated to the first Cu-II by an oxygen atom of its carboxyl group and to the second Cu-II by the nitrogen atom of its pyridine ring, while the other is coordinated to the same two Cu-II atoms in a similar way, but the other way round. Environment about the copper(II) atom for 4 and 5 is a square bipyramid (4+2). In complex 6 both Cu-II central atoms are bridged only by an axial water molecule forming a dimeric structure with the considerably long separation of Cu-II atoms of 5.194 angstrom and the angle Cul-O3-Cula of 150.79 degrees. Moreover, results of the quantitative determination of antimicrobial activity of the complexes as well as above organic ligands alone are discussed. (c) 2007 Elsevier B.V. All rights reserved.