Mixed-valence properties of a dinuclear ruthenium complex bridged by bis(phenylcyanamido)tetrazine

The novel bridging ligand 3,6-bis(phenylcyanamido)-1,2,4,5-tetrazine (tdpcH(2)) and its dinuclear complex [{Ru(ttpy)(bpy)}(2)(mu-tdpc)][PF6](2) were prepared and characterized by elemental analysis and 1H NMR spectroscopy. Cyclic voltammetry and vis-NIR and IR spectroelectrochemistry of [{Ru(ttpy)(bpy)}(2)(mu-tdpc)](2+) showed that [{Ru(ttpy)(bpy)}(2)(mu-tdpc)](3+) is a Class II mixed-valence system with metal-metal coupling of 400 cm(-1) assuming a transition dipole moment length of 21 angstrom. DFT calculations of tdpc(2-) suggested that the stability of the HOMO results in weak metal-metal coupling via the hole-superexchange mechanism.