Transient DC Photocurrent Investigation of Charge Redistribution within Re(CO)₃Cl(2,2‘-bipyridine): An Unexpected Decrease in Molecular Dipole Moment upon Emissive Excited-State Formation

Transient DC photocurrent measurements were performed on Re(CO)3Cl(2,2‘-bipyridine). The observed negative signal is indicative of a decrease in the magnitude of the dipole moment upon the formation of the emissive charge-transfer excited state. ZINDO-1 calculations on the closely related complex Mn(CO)3Cl(2,2‘-bipyridine) corroborate this unexpected finding. A comparison between the transient DC photoconductivity technique and electronic Stark spectroscopy is presented.