Mixed ligand complexes of osmium (II/III/IV)-2,2'-dipyridylamine: synthesis and redox behavior

摘要

Eight mixed ligand compounds of osmium (II), -(III),-(IV) of general formula, |Os(dpya)L_2|~(Z+) [dpya = 2,2'-dipyridylamine; L = 2-(phenylazo) pyridine (L~1), 2-(m-tolylazo) pyridine (L~2), 2,2'-bipyridyl (L~3), quinolin-8-olate (L~4) or 2-methylquinolin-8-olate (L~5); z = 1-3] have been prepared, isoalted as their perchlorates. The complexes exhibit several spin-allowed and spin-forbidden charge-trasnfer transitions in the 200-1000 nm region. In MeCN solutiosn the chelates display Os~(IV)-Os~(III) and Os~(III)-Os~(II) couples. The stability of metal oxidation levels is discussed in terms of the electrochemical results and correlated to the pi-acceptor properties of these ligands. On the negative side of SCE sucessive ligand reductions in L~1-L~3 complexes are observable.