GROUND-STATE VIBRATIONS OF TROPYLIUM CATION (C7H7- AN AB-INITIO STUDY() )

The ground state vibrational frequencies and cartesian force constants of cycloheptatrienylium (tropylium) cation (C7H7+) are obtained using ab initio molecular orbital theory at HF/4-21G and HF/6-31G* levels. A set of scale factors in non-redundant local symmetry coordinates ar e obtained by fitting the ab initio frequencies to the experimental on es of benzene at the same levels of theory. The scale factors of benze ne are used to scale the local force constants of C7H7+ and the scaled force constants are in turn used to predict its vibrational frequenci es. The good agreement of the predicted frequencies with the infrared and Raman active fundamentals lends confidence in the predicted number s of inactive fundamentals. (C) 1998 Elsevier Science B.V.