VIBRATIONAL COUPLING IN TRANS-AZOBENZENE AND ITS ISOTOPOMERS

Infrared (4000-400 cm(-1)) and Raman spectra (4000-100 cm(-1)) of six trans-azobenzene isotopomers, including the parent one, were recorded. Using mono and double N-15-labelled isotopomers, the assignment of th e N=N stretching was confirmed at 1439 cm(-1) in the parent isotopomer . This vibration is strongly coupled with the phenyl mode 19b. In isot opomers with one and two perdeuterium-labelled phenyl groups the N=N s tretching shifts to higher wavenumbers, since this coupling is no long er effective. (C) 1997 Elsevier Science B.V.