Polymeric heterometallic dicarboxylates [MIIx(VIVO)xL2x(H2O)y] (MII=Ba, Mn; L=Me2mal, Bumal) and their electrochemical study on solid and composite paste electrodes

The main goal of this work was to obtain VIV–BaII and VIV–MnII heterometallic dycarboxylates, to characterize their structures, magnetic properties and to investigate the possibility of using obtained compounds in composite paste electrodes. The reactions of vanadyl sulfate VOSO4·3H2O with barium salts of dimethylmalonic (H2Me2mal = C3H6(COOH)2) and butylmalonic (H2Bumal = C4H10(COOH)2) acids taken in a ratio of 1:2 in aqueous solution gave crystals of the coordination polymers {[Ba(VO)(Me2mal)2(H2O)]·H2O}n (1) and {[Ba3(VO)3(Bumal)6(H2O)13]·4H2O}n (2), respectively. The crystal structures of the compounds are built of mononuclear bis-chelate metal fragments containing vanadium(IV), which are bridged to barium ions by carboxylate groups. The reactions of the synthesized compounds with manganese(II) sulfate in aqueous solutions were found to give new heterometallic polymers 3 and 4 {[Mn(VO)(L)2(H2O)5]·H2O}n (L = Me2mal in 3 and L = Bumal in 4), which retain the bis-chelate vanadyl moiety formally acting as a vanadium-containing O-donor ligand. Compounds 1–4 were studied by cyclic voltammetry in solution and as composites in paste electrodes; the potential values as well as localization sites of oxidation and reduction processes were determined.