VIBRATIONAL-SPECTRA OF S-TRIAZINE AND ITS HALOGENATED DERIVATIVES - HARMONIC SCALED AB-INITIO FORCE-FIELDS FOR S-TRIAZINE, TRIFLUORO-S-TRIAZINE AND TRICHLORO-S-TRIAZINE

The vibrational spectra of s-triazine, trifluoro-s-triazine and trichl oro-s-triazine were calculated by using the 3-21G basis set and the pr ogram system GAUSSIAN 90. The ab initio force fields were scaled to tr y to reproduce the best values assigned for experimental frequencies f or the above-mentioned molecules. The transferability of the scale fac tors among these molecules was also studied. Taking into account the r esults obtained, and with the help of new IR and Raman spectra, the no rmal mode nu(12) of trifluoro-s-triazine has been reassigned. Likewise , the assignment proposed by Lancaster et al. [J.E. Lancaster, R.F. St amm and N.B. Colthup, Spectrochim. Acta, 17 (1961) 155] for the normal mode nu(11) of s-triazine has been confirmed. New values for the inac tive modes in IR and Raman spectra, nu(4) and nu(5), have also been ca lculated.