Dinuclear Ru^IIPHEHAT and -TPAC Complexes:  Effects of the Second Ru^II Center on Their Spectroelectrochemical Properties

Four novel dinuclear Ru^II compounds and, for comparison purposes, two corresponding mononuclear complexes containing the PHEHAT or TPAC ligand (PHEHAT = 1,10-phenanthrolino[5,6-b]-1,4,5,8,9,12-hexaazatriphenylene and TPAC = tetrapyrido[3,2-a:2‘,3‘-c:3‘ ‘,2‘ ‘-h:2‘ ‘‘,3‘ ‘‘-j]acridine) have been synthesized and characterized. Conclusions on the effects of dinucleation of these two bridging ligands can be drawn only for the compounds for which the results demonstrate that the bridging ligand is involved in the first electrochemical reduction and lowest emission energy. The behavior of these complexes, which is not always predictable, is discussed, and the differences are highlighted in this work. Interestingly, all of the compounds are luminescent except one dinuclear species, [(phen)₂Ru-μ-PHEHAT-Ru(TAP)₂]⁴⁺, which does not luminesce in MeCN and BuCN at room temperature.