Bond Evolution in Electron Transfer: A Time-Resolved EXAFS Study

The photoinduced electron transfer reaction of [Co(III)(NH(3))(6)](3+) complex, after 266/267 nm excitation in the charge transfer band, has been studied by means of ultrafast EXAFS, optical transient spectroscopy, and quantum chemistry calculations. The Co-N bond length changes and the transient spectra and kinetics have been measured and in combination with DFT theoretical calculations are used to determine the photochemical mechanism of the Co(III) to Co(II) redox reaction. The data presented show that the Co-N bond length changes from the Co(III)-N 1.93 A length to the 2.12 A Co(II)-N length within 2 ps and then remains constant for at least 100 ps. This strongly implies that intramolecular electron transfer from the ligand to cobalt occurs during the first 2 ps after excitation. Low quantum yield electron photodetachment from [Co(III)(NH(3))(6)](3+) complex has also been observed.