Aa. Elazhary, VIBRATIONAL ANALYSIS OF THE SPECTRA OF 1,2,5-OXADIAZOLE, 1,2,5-THIADIAZOLE AND 1,2,5-SELENADIAZOLE, Acta chemica Scandinavica, 49(1), 1995, pp. 11-19
Equilibrium geometries and harmonic force fields have been calculated
for 1,2,5-oxadiazole, 1,2,5-thiadiazole and 1,2,5-selenadiazole at the
SCF and MP2 levels of theory using the 6-31G* basis set (Binning-Cur
tiss for the selenium atom). Scaled quantum-mechanical (SOM) force fie
lds have been calculated for the three molecules and some of their iso
topomers using the experimental frequencies available from the literat
ure. The IR absorption intensities were calculated using the computed
dipole derivative tensors. The assignment of the experimental to the c
alculated frequencies was done first according to symmetry then mainly
according to frequency order. The calculated vibrational spectra for
the studied molecules by the scaled MP2 force fields are only slightly
better than those calculated by the scaled SCF force fields. A good c
orrelation was found between the scale factors obtained for both molec
ules and those obtained for 1,3,4-oxadiazole and 1,3,4-thiadiazole.