Abstract
Abstract It has been found that Vaska's compound, Ir(CO)CI(PPh 3 2 (O 2 , eliminates singlet oxygen (3%) by irradiation, which is in contrast to results from previous work. Ir(CO)CI(PPh 3 ) 2 (O 2 ) was photolysed by a 308 nm laser pulse in degassed solvents. The singlet oxygen formed was detected by its emission at 1276 nm ( 1 Δ g → 3 Σ − g ). The nature of the emission was confirmed by the dependence of its lifetime on the solvent and the fact that it was quenched in methylene chloride by DABCO with a rate constant of 1 × 10 8 M −1 s −1 . The related complexes Ir(CO)X(PPh 3 ) 2 (O 2 ) (where XBr and I) and [Ir(dppe) 2 (O 2 )]Cl were also examined in respect to produce singlet oxygen by photolysis. With the exception of [Ir(dppe) 2 (O 2 )Cl, small amounts of singlet oxygen could be detected. Additionally, the wavelength dependence of the photolysis quantum yields shows that the observed photoelimination of oxygen obviously occurs from a higher excited electronic state. The excited state responsible for the elimination is likely to possess significant O δ− 2 → Ir δ+ LMCT character.
Published Version
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