Picosecond time-resolved infrared investigation into the nature of the lowest excited state of fac-[Re(Cl)(CO) 3(CO 2Et-dppz)] (CO 2Et-dppz = dipyrido[3,2a:2′,3′c]phenazine-11-carboxylic ethyl ester)

Abstract

The photophysics of the fac-[Re(Cl)(CO) 3(CO 2Et-dppz)] (CO 2Et-dppz = dipyrido[3,2a:2′,3′c]phenazine-11-carboxylic ethyl ester) was studied with picosecond time-resolved infrared ( ps-TRIR) spectroscopy in metal carbonyl (2100–1800 cm −1) and organic ester (1800–1600 cm −1) spectral regions. The ps-TRIR spectra in both regions give evidence for the formation of a metal-to-ligand charge transfer (MLCT) excited state. The magnitude of ν(CO) shift in the metal carbonyl region of the excited state relative to those of the ground state allows the excited state to be described more precisely as a dπ(Re) → π* (phenazine) 3 MLCT state.