SEMI-EMPIRICAL MOLECULAR ORBITAL CALCULATIONS - ELECTRONIC STRUCTURE AND SPIN-ORBIT COUPLING IN AZABENZENES

Electronic structures of pyridine, pyrazine, pyrimidine and pyridazine are studied by a semiempirical SCF method for valence electron systems previously proposed by the present authors. The charge distributions, transition energies and oscillator strengths of these compounds are calculated. The calculated results show fairly good agreement with the observed ones. Using these results, we have further calculated the oscillator strengths of singlet-triplet transitions {Mathematical expression} and the life times of the triplet states (τ). In this treatment, we have considered the mixing of various singlets with T1 and triplets with S0, and the effect of σ-electrons is studied. © 1969 Springer-Verlag.