VANADIUM METABOLISM IN TUNICATES - THE COORDINATION CHEMISTRY OF V(III), V(IV), AND V(V) WITH MODELS FOR THE TUNICHROMES

Two isomeric tunichrome model compounds have been prepared from spermidine and trihydroxybenzoic acid. The coordination chemistry of these ligands with V(III), (IV), and (V) are reported. Vanadium(V) is found to undergo rapid reduction to V(IV) in the presence of these ligands. Vanadium(IV) complexes were characterized by optical and EPR spectroscopy as well as elemental analysis and magnetic measurements. Vanadium(III) also reacts rapidly with these ligands, producing what is thought to be a V-O-V dimer in acidic solution. The biological implications of the coordination chemistry reported herein with respect to vanadium metabolism in ascidians is discussed.