PNNL

Abstract

Like the Re analog, the ligand-to-metal charge transfer (LMCT) excited state of [Tc(dmpe)3]2+* (dmpe is bis-1,2-(dimethylphosphino)ethane) is luminescent in solution at room temperature. Surprisingly, both [M(dmpe)3]2+* species have extremely oxidizing excited state potentials (ESPs)-the highest for any simple coordination complex of a transition metal. Furthermore, this potential is available using a photon of visible light (calculated for M=Re(Tc); E1/2*=+2.61(2.52)V vs. SCE; ?max =526(585) nm). Using a Rehm-Weller analysis with a series of aromatic hydrocarbons as electron transfer quenchers, E1/2(Re2+*/Re+) has been determined to be 2.58 V, in good agreement with the calculated value. Both [M(dmpe)3]2+* species are quenched by chloride ion and both can function as excited state oxidants in water solution.