COMPARATIVE SEMIEMPIRICAL AND AB-INITIO STUDY OF THE HARMONIC VIBRATIONAL FREQUENCIES OF ANILINE .1. THE GROUND-STATE

The harmonic vibrational frequencies of the ground state S0 of aniline obtained from various ab initio methods [6-31G, 6-31G() and 6-31G* b asis sets] and semiempirical methods (MINDO/3, MNDO, AM1 and PM3) have been compared to the experimental vibrational spectra. Detailed theor etical analyses of the atomic Cartesian displacements of all normal mo des are presented. The semiempirical PM3 method reproduces the experim ental frequencies of aniline with comparable accuracy to the ab initio methods. The PM3 method will be useful in predicting the vibrational spectra of larger aromatic amines.