Crystal and Molecular Structure of The Mixed-Metal Manganese(II) and Cobalt(II) Maleate Complex: [CoхMn1-x(OOCCH=CHCOO).(H2O)2]n

Abstract

For the first time, by the interaction of cobalt maleate tetrahydrate with Mn(II) acetate, a polymeric polynuclear mixed-metal maleate complex of manganese(II) and cobalt(II) was obtained: [CoхMn1-x(OOCCH=CHCOO).(H2O)2]n. The composition and structure of the resulting complexes were studied by IR spectroscopy, UV-Vis spectroscopy, EPR, and elemental and thermogravimetric analysis. The crystal structure of the complex was established by X-ray diffraction. The results of X-ray diffraction analysis showed that maleic acid dianions coordinate with Mn(II) and Co(II) ions in the bidentate bridging form, forming seven-membered chelate rings with manganese and cobalt ions. Each metal ion achieves octahedral symmetry with coordination from two oxygen atoms of two water molecules and two bridging oxygen atoms of the maleate ligands of neighboring complex molecules. The electronic absorption spectra show the absorption band at 965 nm, which should be attributed to the Mn(II) complex. The band at 516 nm refers to the cobalt complex. In the EPR spectrum, a wide single band with g = 2.031 is observed, indicating an electronic exchange interaction between Mn(II) and Co(II) ions. The presence of two metal ions in the complex was also confirmed by cyclic voltammetry. The voltammograms clearly show two reduction waves related to the two-electron reduction of Co2+ (Ec= -0.69 V) and Mn2+ (Ec= -0.985 V) ions.