DENSITY-FUNCTIONAL THEORY STUDY OF VIBRATIONAL-SPECTRA .2. ASSIGNMENT OF FUNDAMENTAL VIBRATIONAL FREQUENCIES OF FULVENE

Ab initio restricted Hartree-Fock (RI-IF) and density function theory calculations using Becke's exchange and Lee-Yang-Parr's correlation functionals (BLYP) were carried out to study the molecular structure and vibrational spectrum of fulvene. Comparison of the calculated and experimental results indicates the density functional BLYP/6-31G* method is more accurate in predicting fundamental vibrational frequencies than the scaled Hartree-Fock approach. On the basis of the calculated results, reassignment of some fundamental vibrational modes of fulvene is proposed. This study shows that density functional theory is a very promising method for understanding the vibrational spectra of organic compounds.