PHOTOPHYSICAL BEHAVIOR OF A NEW CO2 REDUCTION CATALYST, RE(CO)(2)(BPY)(P(OET)(3))(2)(+)

The photophysical and photochemical properties of the cation Re(CO)(2) (2,2'-bipyridyl){P(OEt)(3)}(+)(2) (P+), which is an effective photoche mical reductant of CO2, are examined by time-resolved infrared spectro scopy (TRIR) of the nu(CO) absorption bands, by UV/visible flash photo lysis in both emission and absorption, and by spectroelectrochemistry in both infrared and UV/visible regions. It is shown that P+ is first excited into a metal to ligand charge transfer state (MLCT) in which t he charge is localized on the bpy ligand, resulting in an upward shift in the nu(CO) bands. This excited state is quenched by 1,4-diazabicyc lo[2.2.2]octane to form the neutral species P with lowered nu(CO) infr ared bands; there is a rapid back-reaction between P and DABCO. The ki netics of these processes are obtained. Preliminary experiments sugges t that P must be further activated before the CO2 reduction cycle star ts.