Application of Resonance Raman Spectroscopy to Electronic Structure in Metal Complex Excited States. Excited-State Ordering and Electron Delocalization in Dipyrido[3,2-a:2',3'-c]phenazine (dppz): Complexes of Re(I) and Ru(II)

Excited-state ordering and electron delocalization in Dipyrido[3,2-a:2`,3`-c]phenazine (dppz): Complexes of Re(I) and Ru(II). From excitation-dependent, resonance Raman measurements on [Ru(dmb){sub 2}(dppz)]{sup 2+} (dmp is ,4`-dimethyl-2,2`-bipyridine; dppz is dipyrido [3,2-a:2`,3`-c]phenazine) in CH{sub 3}CN a metal-to-metal ligand charge transfer (MLCT) band at 450 nm is Ru{sup II} (d{pi}){r_arrow} dmb ({pi}){sup *} in character with Ru{sup II}(d{pi}){r_arrow}dppz ({pi}){sup *} appearing as a shoulder at {approx} 490 ligand and point to delocalization of the excited electron over the entire ligand framework. From transient resonance Raman measurements on fac-[Re(dppz)(CO){sub 3-}(PPh{sub 3})] + (PPh{sub 3} is triphenylphosphine) and fac-[Re(dppz)(CO){sub 3-}Cl], the lowest excited state in both is dppz-localized {sup 3}{pi}{pi}{sup *} in character even though the chloro complex is a MLCT emitter.