Photo-induced magnetized state of Co(DTBSQ)(DTBCat)(phen) · C₆H₅CH₃ studied by X-ray absorption spectroscopy

A photo-induced magnetized state of Co(DTBSQ)(DTBCat)(phen)· C₆H₅CH₃ (DTBSQ=3,5-di-tert-butyl-semiquinone, DTBCat=3,5-di-tert-butyl-catechol and phen=1,10-phenanthroline) was investigated by Co K-edge X-ray absorption fine structure (XAFS) spectroscopy. In the present experimental setup, about 65% Co is found to stay in the trapped excited state at 11 K during visible-light (532 nm) irradiation. It is revealed from the X-ray absorption near-edge structure (XANES) spectra that the Co electronic structure of the state is essentially identical to that of the high-temperature (HT) phase. Upon irradiation, one electron in DTBCat^2- is transferred to low-spin (LS) Co(III), yielding high-spin (HS) Co(II) and DTBSQ^-. Extended X-ray absorption fine structure (EXAFS) analysis provides information on the first-nearest neighbor N and O distances; the irradiated sample shows the average Co-N,O distance of 1.95±0.04 Å, which lies between those of low-temperature (1.899±0.011 Å) and HT (2.081±0.021 Å) phases, this being consistent with the XANES results.