Infrared and Raman spectra, vibrational assignment, and ab initio calculations of fluoromalononitrile

The infrared spectra (3500-80 cm−1) of gaseous and solid and the Raman spectra (3500-30 cm−1) of liquid with quantitative depolarization values and solid fluoromalononitrile, FHC(CN)2, have been recorded. These spectra have been interpreted in detail and a complete vibrational assignment is proposed based on infrared band contours, depolarization values, and relative infrared and Raman intensities. The assignment is supported by a normal coordinate calculation based upon force constants obtained from MP26-31G∗ ab initio calculations. Also, from these calculations the predicted infrared and Raman spectra have been obtained. The CH bond distance is predicted to be 1.096 Å from the isolated carbon-hydrogen stretching frequency. Optimized geometric parameters have been obtained from RHF6-31G∗, MP26-31G∗ and MP26-311 + + G∗∗ ab initio calculations. These results are discussed and compared with those obtained for some similar molecules.