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 I I K during visible-light (532 nm) irradiation. It is revealed from the X-ray absorption near-edge structure (XANES) spectra that the Cc 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 Angstrom, which lies between those of low-temperature (1.899 +/- 0.011 Angstrom) and HT (2.081 +/- 0.021 Angstrom) phases, this being consistent with the XANES results. (C) 2001 Published by Elsevier Science B.V.