ELECTROCHEMICAL CHARACTERIZATION OF A NEW VANADIUM PENICILLAMINE ESTER COMPLEX

The synthesis and isolation of VO(Pen-OCH3)2 (Pen-OCH3 = the anion of the carboxylate ester of penicillamine) is reported. This is the first report of the isolation of a vanadyl complex with penicillamine ligands. Based on IR data, the structure is proposed to be similar to that of VO(Cys-OCH3)2 (Cys-OCH3 = the anion of the carboxylate ester of cysteine) which is known to be square pyramidal with bonding of trans sulfur atoms and trans nitrogen atoms to vanadium. The oxidation of VO(Pen-OCH3)2 in DMSO is a reversible process at 0.3 V versus SCE followed by a rapid chemical reaction of the initial product. Controlled potential coulometric oxidation did not give reproducible results until a ruthenium mediator was added. Under these conditions the coulometric data indicated a one electron oxidation, as previously reported for VO(Cys-OCH3)2. Thus, these two vanadyl compounds exhibit similar one electron oxidations giving vanadium(V) products.