Preparation, characterization and redox properties of O,O′-geometrical isomers of μ-α and μ-β-aminoisobutyrato Co(II) complexes with N,N′,N",N′"-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane

Two new dinuclear cobalt(II) complexes which, besides macrocyclic ligand N',N',N ",N'''-tetrakis (2-pyridylmethyl)-1,4,8,11-tetraazacyclo (tpmc) contain alpha- or beta-aminoisobutyrato ions (alpha-aibu(-) and beta-aibu(-), respectively) were synthesized. The complexes having general formula [Co-2(aibu)tpmc](ClO4)(3) were characterized by elemental analysis, electronic and IR spectroscopy, magnetic measurements and cyclic voltammetry. it was assumed that in both complexes an exo coordination of the macrocyclic ligand is achieved. Cobalt(II) ions are bridged with O,O'-aminoisobutyrato ligand. Both complexes are stable against air oxidation, whereas the oxidation of the complex containing the alpha-aibu(-) ion by hydrogen-peroxide gave the corresponding mixed-valence Co-II/Co-III complex. The complexes are also electrochemically stable in the potential range from-0,6V to 0,4V vs SCE.