Abstract

The photophysical and phtochemical properties of fac-(RCO 2)ReI(CO)3L (R = ferrocene, L = phen, 2,2′-bpy; R = 4-(dimethylamino)benzyl (4-DMAB), L = phen) were investigated with continuous and flash photolyses. Their properties were compared with those of fac-(CH3CO2)ReI(CO) 3L (L = phen, 2,2′-bpy) complexes. On a femtosecond to 10 ps time scale, the transient spectra of the singlet Re(I) to L charge-transfer excited states, 1MLCTRe→L, of fac-(RCO 2)ReI(CO)3L (R = ferrocene, 4-DMAB) transform into the spectra of two triplet excited states, the 3MLCT Re→L excited state and a Re(I) to RCO2 - charge-transfer excited state, 3MLCTRe→RCO2. The 3MLCTRe→RCO2 and 3MLCTRe→L excited states have lifetimes that span 102 ns to several microseconds. The photodecarboxylation of fac-(RCO2)Re I(CO)3L, initiated in ligand-to-ligand charge-transfer excited states, 3LLCTRe→L, is markedly affected by the positions of the 3MLCTRe→RCO2 and 3MLCTRe→L excited states. In addition, the low energy of 3LLCTRCO2→L in the fac-(RCO2)Re I(CO)3L (L = phen, 2,2′-bpy) complexes, relative to those of fac-(CH3CO2)ReI(CO)3L (L = phen, 2,2′-bpy) decreases the efficiency of the photodecarboxylation reaction. © 2007 American Chemical Society.