Infrared and Raman spectra of 4-(dimethylamino)benzonitrile and isotopomers in the ground state and vibrational analysis

Vibrational analysis of 4-(dimethylamino)benzonitrile (DMABN) has been perf ormed. Infrared and Raman spectra of DMABN and its four different isotope-l abeled species have been recorded. Assignments of the vibrational bands are given on the basis of normal coordinate calculation on an empirical force field and of the Hartree-Fock and the density functional calculations. Most of the vibrational bands observed have been successfully assigned, and the isotope shifts are reasonably explained. It is clearly demonstrated from t he measurements on the isotopomers that assignments of some bands in the li terature are not correct. The characteristics of the empirical and the quan tum-chemical force fields are compared. It has been found that the strong i nteraction between the dimethylamino group and the benzene ring is directly reflected in the force field. (C) 2000 Elsevier Science B.V. All rights re served.