Influence of Ligand with Fine Difference at Donor Site on MMCT Property in Binuclear Mixed Valence Complexes

To investigate how the electronic effect of ligand at donor site influences electronic communication or metal-to-metal charge transfer(MMCT)properties in similar mixed-valence(MV)complexes,a series of binuclear organometallic complexes,MeCp(dppe)RuCNFeCl₃(1),MeCp(PPh₃)₂RuCNFeCl₃(2),Cp^*(dppe)FeCNFeCl₃(3),Cp^*(dppe)RuCNFeCl₃(4)and Cp^*(PPh₃)₂RuCNFeCl₃(5),have been synthesized and characterized.The electronic absorptions of these complexes show the presence of MMCT properties between RuⅡ or FeⅡ and FeⅢ ions,strongly supported by the theoretical calculations.With increasing electron-donating ability of ligands(PPh3>dppe,Cp^*>MeCp)at donor site,the MMCT absorption bands are red-shifted,which expresses in the sequence of absorption bands with 1(500 nm),4(536 nm),2(542 nm),5(580 nm)from high-energy to low-energy.Meanwhile,the MMCT absorption energy of 4(536 nm)is larger than that of 3(760 nm)due to the stronger electron-donating ability of FeⅡ than RuⅡ.Furthermore,these complexes belong to the Class Ⅱ systems according to the Robin and Day’s classification.