A STUDY OF THE STRUCTURES AND VIBRATIONS OF C6H5NH2, C6H5NHD, C6H5ND2, C6D5NH2, C6D5NHD, AND C6D5ND2 IN THE S-1 STATE BY AB-INITIO CALCULATIONS

The structures and vibrations of C6H5NH2, C6H5NHD, C6H5ND2, C6D5NH2, C 6D5NHD, and C6D5ND2 have been studied using ab initio molecular orbita l (MO) calculations. Calculations at the CIS/6-31+G level successfull y predict that aniline is planar in the S-1 state, and contracts along the long in-plane axis with a quinoid-like resonance structure. A com parison of the S-0 and S-1 state vibrational modes is presented and di scussed in terms of the changes in reduced masses, force constants, an d mode mixing for aniline and its isotopic species. The computed frequ encies are found to be in very good agreement with the available exper imental values. (C) 1998 Elsevier Science B.V.