Synthesis, spectral properties, crystal structures and antimicrobial effects of copper(II) pyridinecarboxylate adducts with chelating ligands

Abstract

The reaction of an ethanolic solution of copper(II) pyridinecarboxylates CuX 2· nH 2O (where X is nicotinate (nic) ( n=0) or isonicotinate (isonic) ( n=4)) with ethylenediamine (en) in a molar ratio of 1:2 lead to the isolation of solid tetragonally distorted octahedral complexes of the type [Cu(en) 2(H 2O) 2]X 2· nH 2O ( n=1 for nic; n=0 for isonic). The analogous reaction of CuX 2· nH 2O with diethylenetriamine (dien) in a molar ratio of 1:1 leads to the formation of square-pyramidal pentacoordinated complexes of the type [CuX(dien)(H 2O)]X. On the other hand, the reaction of equimolar quantities of copper(II) nitrate and dien with nicotinate anions (equimolar quantities of pyridinecarboxylic acid and NaOH) in ethanolic solutions gives a solid monomeric complex [Cu(nic)(NO 3)dien)(H 2O)]·H 2O in which the coordination polyhedron around the Cu(II) atom is a (4+1+1) distorted tetragonal bipyramid. Based on the molecular structure the electronic and IR spectra are discussed. Moreover, the results of the quantitative determination of antimicrobial activity of the isonic complexes [Cu(isonic) 2(H 2O) 4], [Cu(en) 2(H 2O) 2](isonic) 2, [Cu(isonic)(dien)(H 2O)](isonic), as well as isonicotinic acid, ethylenediamine and diethylenetriamine alone are discussed.