Density functional theory study of vibrational spectra .3. Assignment of fundamental vibrational modes of quadricyclane

Density functional theory BLYP (Becke's exchange and Lee-Yang-Parr' a correlation functionals), ab initio Hartree-Fock (HF) and hybrid DFT/HF B3LYP calculations were carried out to study the structure and vibrational spectra of quadricyclane. The BLYP/6-31G* and scaled HF/6-31G* frequencies correspond well with each other and with available experimental assignment of the fundamental vibrational modes. Based on conformity between the calculated and experimental results, a plausible assignment of two remaining a(1) modes and all non-CH stretching a(2), b(1), and b(2) modes is proposed.