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)2nic}2(H2O)]2 (1), [Cu{2,6-(MeO)2nic}2(H2O)]2 · 3DMF (2), where 2,6-(MeO)2nic 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]X2, where X is 2,6-(MeO)2nic (4) or 3-pyacr (5) and en is ethylenediamine, and [Cu(3-pyacr)2(dien)(μ-H2O)0.5]2 · 7H2O (6), where dien 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 CuII by an oxygen atom of its carboxyl group and to the second CuII by the nitrogen atom of its pyridine ring, while the other is coordinated to the same two CuII 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 CuII central atoms are bridged only by an axial water molecule forming a dimeric structure with the considerably long separation of CuII atoms of 5.194 Å and the angle Cu1–O3–Cu1a of 150.79°. Moreover, results of the quantitative determination of antimicrobial activity of the complexes as well as above organic ligands alone are discussed.

Graphical abstractSynthesis, spectral and magnetization data, and crystal structures as well as antimicrobial activity of [Cu{2,6-(MeO)2nic}2(H2O)]2, [Cu{2,6-(MeO)2nic}2(H2O)]2 · 3DMF, where 2,6-(MeO)2nic is 2,6-dimethoxynicotinate and DMF is N,N-dimethylformamide, [Cu(3-pyacr)2(H2O)2]n, where 3-pyacr is trans-3-(3-pyridyl)acrylate, [Cu(en)2(H2O)2]X2, where X is 2,6-(MeO)2nic or 3-pyacr and en is ethylenediamine, and [Cu(3-pyacr)2(dien)(μ-H2O)0.5]2 · 7H2O, where dien is diethylenetriamine are reported. In complex [Cu(3-pyacr)2(dien)(μ-H2O)0.5]2 · 7H2O, both CuII central atoms are bridged only by an axial water molecule forming a dimeric structure with the considerably long separation of CuII atoms of 5.194 Å and the angle Cu1–O3–Cu1a of 150.79°.Figure optionsDownload full-size imageDownload as PowerPoint slide