Accessing the triplet manifold of naphthalene benzimidazole-phenanthroline in rhenium(I) bichromophores.

The steady-state and ultrafast to supra-nanosecond excited state dynamics of -[Re(NBI-phen)(CO)(L)](PF) (NBI-phen = 16H-benzo[4',5']isoquinolino[2',1':1,2]imidazo[4,5-][1,10]phenanthrolin-16-one) as well as their respective models of the general molecular formula [Re(phen)(CO)(L)](PF) (L = PPh and CHCN) has been investigated using transient absorption and time-gated photoluminescence spectroscopy. The NBI-phen containing molecules exhibited enhanced visible light absorption with respect to their models and a rapid formation (<6 ns) of the triplet ligand-centred (LC) excited state of the organic ligand, NBI-phen. These triplet states exhibit an extended excited state lifetime that enable the energized molecules to readily engage in triplet-triplet annihilation photochemistry.