Raman and far‐infrared study of the polar single crystals of 3‐(4‐chlorophenyl)‐2‐cyanopropenonitrile

Abstract

Low-frequency Raman and infrared spectra of a single crystal of 3-(4-chlorophenyl)-2-cyanopropenonitrile have been obtained and an assignment of the bands to their symmetry species has been made. Normal coordinate calculations using a dynamic lattice model with only a short-range atom-atom potential confirm roughly the experimental assignments but suggest the need to introduce an electrostatic potential in the lattice mode calculation of this polar crystal. Polarized infrared reflection spectra have been studied in order to determine the longitudinal and transverse optical frequencies, damping factors, oscillator strengths and induced dipole moments of the optical phonons. Approximate dynamic charges on the C S N groups and on the whole molecule were estimated.