Infrared studies of iodine complexes with several aromatic amines

Abstract

The infrared spectra of charge transfer complexes formed by iodine with fifteen aromatic amines were recorded in the 3200-̄3600 and 700-̄1400 cm −1 ranges. The frequency shifts of the fundamental symmetric and asymmetric NH2 stretching vibrations that occur as a result of complex formation have been studied in relation to the donor properties of the aromatic amines. The HNH bond angle, the NH stretching force constant, and the “s character” of the hybrid orbitals of the nitrogen atom were calculated from the two shifted frequencies; the characteristic differences between complexed and uncomplexed amines were interpreted in terms of the calculated intermolecular charge transfer. Other spectral changes due to complex formation were: a characteristic decrease of the νCN stretching frequency, as well as some small shifts of the αCH and γCH vibrations: a new band which appeared in several cases in the 800 cm−1 region was assigned to the enhancement of the out-of-plane deformation vibration of the amino group.