CELL-EXPANSION OF TRIS(2,4-PENTANEDIONATO)CHROMIUM AND -ALUMINUM UNDER LIGHT IRRADIATION

In the previous letter,(1) we have reported on the cell-expansion and contraction of platinum( II) complexes under light irradiation and dis cussed the results in the term of the molecular structures in the exci ted states. For tris(2,4-pentanedionato)chromium and -aluminum (abbrev iated as Cr(acac)(3) and Al(acac)(3), respectively), we also found the cell-expansion under light irradiation. The Xray powder patterns of t hese complexes were shifted to low reflect-angle than original one by light absorption of the complexes. The shift of X-ray powder pattern o f Al(acac)3 is due to thermal cell-expansion caused by internal conver sion of the molecule under light irradiation. In case of Cr(acac)(3), however, the shifts are due to not only the thermal cell-expansion but also another reason concerned with the structures in the excited stat es.