Photo-illumination effects have been measured for [CoIII-LS (phen)(3,5-DBSQ)(3,5-DBCat)]·C6H5Cl, where LS, phen, 3,5-DBSQ and 3,5-DBCat denote low-spin, 1,10-phenanthroline, 3,5-di- tert -butyl-1,2-semiquinonate and 3,5-di- tert -butyl-1,2-catecholate, respectively. When the Co compound was illuminated at 5 K, the magnetization value, μ eff increased from 1.7 to 2.7 μ B. The UV-Vis absorption spectra after illumination show that the absorption band at around 800 nm, characteristic of the [CoII-HS(phen) (3,5-DBSQ)2] state (HS denotes high-spin), increased and the charge transfer band from 3,5-DBCat to 3,5-DBSQ at 2500 nm was reduced. IR spectra show that the C-O stretching peak at 1280 cm-1 is significantly decreased. These results confirm that a photo-induced intra-molecular electron transfer, [CoIII-LS(phen)(3,5-DBSQ)(3,5-DBCat)]·C6 H5Cl↔[CoII-HS(phen)(3,5-DBSQ)2] ·C6H5Cl, was induced by 532 or 830 nm light. The relaxation kinetics of valence tautomerism was studied. For T≥25 K, kVT0=0.205 s-1 and Ea=110.38 cm-1. Below 25 K, the rate constant for the valence tautomeric relaxation as T approaches the 0 K, which suggests that tunneling is the predominant mechanism for the relaxation.
|Number of pages||5|
|Journal||Journal of Photochemistry and Photobiology A: Chemistry|
|Publication status||Published - Oct 1 2004|
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Physics and Astronomy(all)