Normal Modes ofp-Aminobenzonitrile andp>-Dimethylaminobenzonitrile. Vibrational Spectra and PM3 Calculations with a Modified Scaling Procedure

In addition to IR spectra, polarized Raman spectra of p-aminobenzonitrile and p-dimethylaminobenzonitrile in acetonitrile solution were recorded with different excitation wavelengths. Normal mode coordinates were calculated using a modified PM3 program package. Instead of only scaling the calculated wavenumbers of the resulting normal modes, a scaling factor was introduced into the force field. Since the normal coordinate pictures of several modes change owing to different mixing of local modes, a modified assignment for several modes is proposed.