Theoretical and experimental (400-10000 cm(-1)) study of the vibrational spectrum of pentachlorophenol

Geometric and vibrational spectroscopic data (bond distances and angles, vi brational frequencies, infrared intensities) of pentachlorophenol-OH (PCP-O H) and pentachlorophenol-OD (PCP-OD) are calculated by density functional t heory (B3LYP) using the 6-311G(d, p) basis set. Except for the vibrations i nvolving the OH bond, the agreement between the experimental and calculated fundamental frequencies between 3600 and 400 cm-L is very good. The theore tical method failed, however, to reproduce quantitatively the experimental intensities. The infrared spectra between 3600 and 10 000 cm(-1) are studie d, and the overtones or combination bands are assigned by comparing the spe ctra of POP-OH and PCP-OD. The difference between the experimental and theo retical frequencies of the nu(OH) and nu(OD) frequencies can be mainly acco unted for by the neglect of the anharmonicities of these vibrations in calc ulations. The binary or ternary combinations characterized by the highest c oupling constants and the highest intensities are those involving the nu(PH ), delta(OH), gamma(OH), and nu(C-O) vibrations, (C) 1999 Academic Press.