A study of novel cobalt(II) octaazamacrocyclic complexes with aminocarboxylates or their derivatives

Abstract

Four new air-stable mixed-ligand Co(II) complexes having the general formula [Co2(Y)tpmc]Z3×q(H2O/CH3CN) (HY = N-methylglycine/N,N-dimethylglycine, Z = - 4BF , qH2O=4 or 3; HY=S-norvaline/S-valine Z=-ClO4 , qCH3CN = 0.5; qH2O = 0.5; tpmc = N,N',N'',N'''-tetrakis(2-pyridylmethyl)- -1,4,8,11-tetraazacyclotetradecane) were prepared. The composition, some physical and chemical properties and their tentative geometries were evaluated based on elemental analysis (C, H, N), conductometric and magnetic measurements, spectroscopic data (UV/Vis, IR) and cyclic voltammetry. The data were compared with earlier described analogous complexes containing the macrocyclic ligand and aliphatic aminocarboxylates. It is assumed that all complexes are binuclear with an exo coordination mode of the octaazamacrocyclic pendant ligand in the boat conformation. In addition, two -N-(CH2)2-N- portions of the cyclam ring within the tpmc ligand and Co(II) ions in the high-spin state are most probably bridged via oxygen atoms from the anion of the aminocarboxylate/derivatives, whereas nitrogen atoms rest uncoordinated. In all cases, a combined chelate-bridged coordination is proposed as the most probable. The complexes were electrochemically stable in the potential range -1.0 to 1.0 V. They were also preliminary assayed toward some microorganisms together with the ligands, starting simple salts and solvents as test substances. In some cases, certain antimicrobial activity of the complexes was detected.

Keywords

• cobalt(ii) complexes
• pendant octaazamacrocycle
• aminocarboxylates and derivatives