Raman spectroscopic verification of fac-Sc(PMBP)3 by solid and solute spectra and density functional method calculation

Two kinds of solids were obtained for Sc(PMBP)3 by precipitation from different solvents. They were light-yellow crystal and yellowishwhite powder, and their melting points were 209 and 217 8C, respectively. Raman spectra of six anhydrous samples prepared from these materials were measured and classified into two types of spectral patterns. Raman solute spectra of these two materials were measured in a dilute solution of dichloromethane, in which the solute is a free molecule in a solvent cage. Their spectra were considerably similar to each other, but they indicated clear differences in some pairs of bands. One of these two molecules was concluded to be a facial form of Sc(PMBP)3, because the other constituent has been established to be a meridional form of Sc(PMBP)3 by X-ray analysis of a single crystal. Structural optimization for mer- and fac-Sc(PMBP)3 and their vibrational calculation of frequencies and intensities were carried out with the density functional method of B3LYP/6-31G**. Their computed Raman spectra were well coincident with their observed spectra. The existence of fac-Sc(PMBP)3 has been established by thermal analysis, Raman spectroscopy and ab initio calculation. q 2005 Elsevier B.V. All rights reserved.