Vibrational sidelines in the localized 3MLCT luminescence of [Ru(bpy)3−x(L)x]2+ (x=0 to 3, L = 3,3′-bipyridazine, bpy-d8) in the C2/c [Zn(bpy)3](ClO4)2 lattice Original Research Article

A detailed examination of the spectroscopy of the [Ru(bpy)3−x(bprid)x]2+ (bprid = 3,3′-bipyridazine, x = 0 to 3) series doped in [Zn(bpy)3](ClO4)2 is presented. The 3MLCT transitions to the bprid ligand are ≈ 3000 cm−1 lower in energy than corresponding transitions involving the bpy ligand. The [Ru(bpy)2(bprid)]2+ complex probes the C2/c structure of the host. An energy difference of ≈ 360 cm−1 is observed for the 3MLCT transitions involving the bprid ligand in the two crystallographically distinct positions. For the complexes with x=2 and 3, fast intramolecular excitation energy transfer ensures that the emission occurs from the Ru-bprid subunit with the lowest excited state. Excitation line narrowing experiments show that the excitation exchange interaction between Ru-bprid subunits must be less than ≈ 0.5 cm−1. The transferred electron resides on one bprid ligand in the lowest-excited states. Vibrational sidelines in the luminescence spectrum corresponding to bpy modes are observed for the [Ru(bpy)2(bprid)]2+ complex over the entire frequency range. Excitation line narrowing experiments and a careful examination of the vibrational sidelines in the luminescence of the [Ru(bpy)3−x(bpy-d8)x]2+ series (x = 0 to 3) are presented. The simultaneous appearance of bpy and bpy-d8 vibrational modes for the x = 1 and x = 2 systems is discussed.