We are investigating fundamental processes for the efficient capture and chemical conversion of solar energy using transition metal complexes. Mechanistic and kinetic knowledge of photo-induced multi-electron transfer reactions and bond forming (and/or breaking) reactions is crucial to understanding photochemical activation of CO2 and to the design of more efficient photoconversion systems. We have investigated the excited state properties and the reactivities of the photochemically produced species of fac-Re(dmb)(CO)3X (where dmb = 4,4′-dimethyl-2,2′- bipyridine, X = halide or solvent) by transient UV-vis, transient FTIR, and NMR spectroscopy. The reduced monomer, Re(dmb)(CO)3S (S = solvent) dimerizes (kd = 40 M-1 S-1) sreversibly in THF. The reaction of Re(dmb)(CO)3S with CO2 is very slow (kCO2 < 0.1 M-1 s-1) and liberates CO with a 25-50% yield based on [Re]. A CO2 bridged dimer, (CO) 3(dmb)Re-CO(O)-Re(dmb)(CO)3, is identified as a key intermediate in the CO formation. [Re(dmb)(CO)3]2(OCO 2), Re(dmb)(CO)3(OC(O)OH) and [Re(dmb)(CO) 3S]+ were detected as oxidation products by means of NMR, IR, and FAB MS.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry