Electronic Structure and Photophysics of Low Spin d 5 Metallocenes.

The electronic structure and photophysics of two low spin metallocenes, decamethylmanganocene (MnCp* 2 ) and decamethylrhenocene (ReCp* 2 ), were investigated to probe their promise as photoredox reagents. Computational studies support the assignment of 2 E 2 ground state configurations and low energy ligand-to-metal charge transfer transitions for both complexes. Weak emission is observed at room temperature for ReCp* 2 with τ = 1.8 ns in pentane, whereas MnCp* 2 is not emissive. Calculation of the excited state reduction potentials for both metallocenes reveal their potential potency as excited state reductants ( E °'([MnCp* 2 ] +/0* ) = -3.38 V and E °'([ReCp* 2 ] +/0* ) = -2.61 V vs Fc +/0 ). Comparatively, both complexes exhibit mild potentials for photo-oxidative processes ( E °'([MnCp* 2 ] 0*/- ) = -0.18 V and E °'([ReCp* 2 ] 0*/- ) = -0.20 V vs Fc +/0 ). These results showcase the rich electronic structure of low spin d 5 metallocenes and their promise as excited state reductants.