Generation and Electron-Transfer Reactivity of the Long-Lived Photoexcited State of a Manganese(IV)-Oxo-Scandium Nitrate Complex

Abstract

Photoexcitation of a manganese(IV)-oxo-scandium nitrate complex ([(Bn-TPEN)Mn-IV(O)](2+)-Sc(NO3)(3)) in a solvent mixture of trifluoroethanol and acetonitrile (v/v=1 : 1) resulted in generation of the long-lived photoexcited state, which is detected by nanosecond laser transient absorption measurements. The transient absorption maximum (lambda(max)) of the E-2 excited state of [(Bn-TPEN)Mn-IV(O)](2+)-Sc(NO3)(3) is observed at 620 nm with lifetimes of 7.1 mu s. The lambda(max) value is blue-shifted and the lifetime becomes longer as compared with the previously reported values of lambda(max) (640 nm) and lifetime (6.4 mu s) of the E-2 excited state of the 1 : 2 complex between [(Bn-TPEN)Mn-IV(O)](2+) and Sc(OTf)(3) ([(Bn-TPEN)Mn-IV(O)](2+)-(Sc(OTf)(3))(2)). The electron-transfer reactivity of the E-2 excited states of [(Bn-TPEN)Mn-IV(O)](2+)-Sc(NO3)(3) was similar to that of [(Bn-TPEN)Mn-IV(O)](2+)-(Sc(OTf)(3))(2). The long lifetime and the high reactivity of the E-2 excited state of [(Bn-TPEN)Mn-IV(O)](2+)-Sc(NO3)(3) provide an excellent photooxidant for oxidation of compounds, which would otherwise be impossible to be oxidized.