Tuning the Excited States in -fac--[Re(X2dppz)(CO)3(L)]: Intraligand, Charge Transfer or both?

Excited state lifetime measurements - emission, emission lifetime and Resonance Raman - have been conducted on the series -fac--[Re(X2dppz)(CO)3(L)]0,+ (L = Cl-, 4-ethylpyridine (4-Etpy), 4,4´-bipyridine (4,4´-bpy)), with the X2dppz substituted dipyrido[3,2-a:2',3'-c]phenazine ligands (X = CH3 and Cl). The results are consistent with closely lying excited states, with pp * lowest, but MLCT contributing significantly to excited state lifetimes for the neutral complexes. -fac--[Re(Cl2dppz)(CO)3Cl] appears to undergo a crossover from lowest pp * to lowest MLCT through the glass to fluid transition