183289-53-4Relevant academic research and scientific papers
Ion-Pair Charge Transfer Photochemistry in Rhenium(I) Borate Salts
McCosar, Brace H.,Schanze, Kirk S.
, p. 6800 - 6808 (1996)
The photophysics and photochemistry of the salt [(bpy)Re(CO)3(py)+][BzBPh3-] (ReBo, where bpy = 2 2′-bipyridine, py = pyridine, Bz = C6H5CH2 and Ph = C6H5) has been investigated in THF and CH3CN solutions. UV-visible absorption and steady-state emission spectroscopy indicates that in THF ReBo exists primairly as an ion-pair. A weak absorption band is observed for the salt in THF solution that is assigned to an optical ion-pair charge transfer transition. Stern-Volmer emission quenching studies indicate that BzBPh3- quenches the luminescent dπ (Re) → * (bpy) metal-to-ligand charge transfer excited state of the (bpy)Re(CO)3(py)+ chromophore. The quenching is attributed to electron transfer from the benzylborate anion to the photoexcited Re(I) complex, (bpy-*)ReII(CO)3(py)+* + BzBPh3- → (bpy-*)ReI(CO)3(Py) + BzBPh3*. Laser flash photolysis studies reveal that electron transfer quenching leads to irreversible reduction of the Re(I) cation to (bpy-*)ReI(CO)3(py). Photoinduced electron transfer is irreversible owing to rapid C-B bond fragmentation in the benzylboranyl radical, PhCH2BPh3* → PhCH2* + BPh3*. Quantitative laser flash photolysis experiments show that the quantum efficiency for production of the reduced complex (bPy-*)ReI(CO)3(py) is unity, suggesting that C-B bond fragmentation in the benzylboranyl radical occurs more rapidly than return electron transfer within the geminate radical pair that is formed by photoinduced electron transfer.
