文摘
A series of RuN6 dinuclear Ru鈥揌bpp complexes (Hbpp is the dinucleating tetraaza ligand 3,5-bis(pyridyl)pyrazole) of general formula {[Rup>IIp>(Rp>2p>-trpy)(MeCN)]2(渭-Rp>1p>-bpp)}p>3+p>, 10p>3+p>鈥?b>14p>3+p>, (Rp>1p> = H, Me, or NO2. and Rp>2p> = H, Me, MeO; see Scheme 1) has been prepared from their Clp>鈥?/sup> or AcOp>鈥?/sup> bridged precursors. The complexes have been characterized by UV鈥搗is, NMR, CV, and some by X-ray. Complexes 10p>3+p>鈥?b>14p>3+p>, Ru2p>II,IIp>, were oxidized by 1 equiv in solution, leading to the mixed valence Ru2p>II,IIIp> complexes 10p>4+p>鈥?b>14p>4+p> containing one unpaired electron and were characterized by EPR and UV鈥搗is鈥搉ear-IR, which showed metal-centered spin and the presence of low-energy IVCT bands. The Hab parameter indicates a relatively strong electronic coupling between the two ruthenium centers (class II). Further two electron oxidation in solution of the 10p>3+p>鈥?b>14p>3+p> led to the formation of EPR silent Ru2p>III,IIIp> complexes 10p>5+p>鈥?b>14p>5+p>, that were further characterized by UV鈥搗is鈥揘IR. TD-DFT calculations are employed to assign the nature of the UV鈥搗is transitions for the complexes in the various oxidation states, which are of metal to ligand charge transfer (MLCT) type for Ru2p>II,IIp> and ligand to metal charge transfer (LMCT) type for Ru2p>III,IIp> and Ru2p>III,IIIp>.