Excited-State Properties of Rh2(O2CCH3)4(L)2(L = CH3OH, THF, PPh3, py)

Abstract
The photophysical properties of Rh2(O2CCH3)4(L)2 (L = CH3OH, THF = tetrahydrofuran, PPh3 = triphenylphosphine, py = pyridine) were explored upon excitation with visible light. Time-resolved absorption shows that all the complexes possess a long-lived transient (3.5−5.0 μs) assigned as an electronic excited state of the molecules, and they exhibit an optical transition at ∼760 nm whose position is independent of axial ligand. No emission from the Rh2(O2CCH3)4(L)2 (L = CH3OH, THF, PPh3, py) systems was detected, but energy transfer from *Rh2(O2CCH3)4(PPh3)2 to the 3ππ* excited state of perylene is observed. Electron transfer from *Rh2(O2CCH3)4(PPh3)2 to 4,4‘-dimethyl viologen (MV2+) and chloro-p-benzoquinone (Cl-BQ) takes place with quenching rate constants (kq) of 8.0 × 106 and 1.2 × 106 M-1 s-1 in methanol, respectively. A kq value of 2 × 108 M-1 s-1 was measured for the quenching of the excited state of Rh2(O2CCH3)4(PPh3)2 by O2 in methanol. The observations are consistent with the production of an excited state with excited-state energy, E00, between 1.34 and 1.77 eV.

This publication has 45 references indexed in Scilit: