Force fields and assignments of the vibrational spectra of acridine and phenazine - an ab initio study

A complete set of force constants and their corresponding scale factors in non-redundant local coordinates were obtained by fitting the in-plane ab in itio Hartree-Fock (HF) vibrational frequencies computed using 4-21G and 6-3 1G** basis sets to the experimental ones, Using these force constants the p otential energy distribution (PED) of the normal modes was obtained and bas ed on the FED the earlier empirical assignments were either confirmed or re assigned for all the in-plane fundamentals. The force constants of acridine and phenazine are compared to those of anthracene to study the similaritie s and differences. Probable assignment is proposed for the out-of-plane fun damentals of acridine based on Durig's simple scaling of the local force co nstants. (C) 2000 Elsevier Science B.V. All rights reserved.