Spectroscopic and Electrochemical Studies of Optically Active Bipyridyl Complexes

[摘要] The tris(2,2'-bipyridine) complexes of ruthenium(II) and osmium(II) have been synthesised and optically resolved. The singly, doubly and triply reduced complexes have been prepared electrochemically and their circular dichroism and luminescence spectra have been measured. Investigation of the absorption, circular dichroism and luminescence spectra of the complexes and their reduced analogues strongly suggest that the added electrons are localised on the individual bipyridine ligands of the complexes. Hence the complexes are best formulated as [M(bipy)n(bipy-)3-n](n-1)+, where M = Ru, Os and n = 0, 1, 2 and 3. In addition, a chemical reduction technique using lithium metal has been developed. This has enabled the infrared spectra of the triply reduced complexes to be measured. The triply reduced ruthenium complex has been found to racemise in dry acetonitrile but is optically stable in dimethylformamide. This has been attributed to a weakening of the ligand field of bipyridine when it is reduced to the anion. Lithium 2,2'-bipyridinyl has been synthesised and complexed with the chiral co-ordinating ligands (-)-sparteine and R and S-tetra-N,N,N',N'-methyl propane-1,2-diamine whereupon its circular dichroism spectra have been measured. The tris(2,2'-bipyridine)iridium(III) complex has been synthesised and optically resolved and its hitherto unknown circular dichroism spectrum has been measured. The complex has been chemically reduced and in addition to the triply reduced complex the quadruply reduced complex has also been synthesised and their absorption and circular dichroism spectra have been measured. Investigation of the circular dichroism spectra again suggest that the added electrons are localised on the individual bipyridine ligands of the complexes.

[发布机构] University:University of Glasgow

[关键词] Inorganic chemistry