Differential ion-pairing and temperature effects on intervalence charge transfer (IVCT) in a series of dinuclear ruthenium complexes

Thermochromism and anion-dependence studies on the intervalence charge transfer (IVCT) properties of the diastereoisomers of [{Ru(bpy)(2)}(2)(mu-BL)](5+) {BL = dpb', dpq', and dpb: dpb' = dipyrido(2,3-a;3',2'-c)benzophenazine; dpq' = dipyrido(2,3-a;3',2'-c)phenazine; dpb = 2,3bis(2-pyridyl)-1,4-benzoquinoxaline} are reported. IVCT thermochromism studies revealed that the level of delocalisation may differ between the diastereoisomers for a system, and a slight temperature dependence in meso-[{Ru(bpy)(2)}(2)(mu-dpb)](5+) which was dependent on the identity of the counter-anion {PF6- or B(C6F5)(4)(-)}Anion effects on the IVCT properties of the diastereoisomeric forms of the three complexes were observed to be somewhat unpredictable. X-ray crystal structure determinations on ineso[{Ru(bpy)(2)}(2)(mu-dpb)](4+) (as the PF6- and [ZnCl4](2-) salts), meso-[{Ru(bpy)(2)}(2)(mu-dpb')](4+) (PF6- salt) and meso [{Ru(bPY)(2)}(2)(mu-dpq')](4+) ([ZnCl4](2-) salt) revealed considerable distortion in the bridging ligand, particularly in the dpb-bridged species where the distortion was also dependent on the anion.