Stereochemical Influences on Intervalence Charge Transfer in Homodinuclear Complexes of Ruthenium

Spectroelectrochemical investigations of two dinuclear complexes [RuIII(bpy)2(μ-BL)RuII(bpy)2]5+ (BL = 2,3-bis(2-pyridyl)-1,4-benzoquinoxaline (dpb); dipyrido(2,3-a;3‘,2‘-c)benzophenazine (dpb‘)) revealed that the intervalence charge transfer (IT) characteristics are sensitive to the stereochemistry. In particular, there appears to be a greater degree of metal−metal interaction in the meso compared with the rac diastereoisomeric form. Thermochromism, redox, and semiempirical computational studies suggest differential ion-paring between the diastereoisomeric forms.