The Raman spectra of some molecular complexes of 1-azabicyclo[2.2.2]octane and 1,4-diazabicyclo[2.2.2]octane

Abstract

The Raman spectra of the molecular complexes of 1-azabicyclo[2.2.2]octane with iodine, bromine, sulfur dioxide, carbon tetrabromide and of 1,4-diazabicyclo[2.2.2]octane with iodine, bromine, sulfur dioxide, carbon tetrabromide, iodoform and phenol have been obtained. The analysis of the spectra indicates that most of the amine vibrational modes undergo shifts upon complexation, whereas for the acceptor molecules such shifts are significant only for the stronger ones. The spectra also show an increase in the number of bands reflecting a lower symmetry in the complexes as compared with the free amines. The most outstanding features in the Raman spectra of this series of molecular complexes is the dramatic intensification of the bands assigned to modes involving mainly NC 3 deformation and CC stretching, both of totally symmetric species. A similar behavior was also noticed in the Raman spectra of hexamethylenetetramine molecular complexes, and in the SER spectra of this series of amines. From the present results it is suggested that the observed enhancements are due to the charge transfer interaction of the amines with systems of large polarizability.