IR absorption spectra and association of acridinium salts with hydrogen halide molecules

Abstract

It was observed that the reaction of acridine with hydrogen halides under heterogeneous conditions proceeds in two steps: An acridinium salt is formed in the first step, while a complex of the salt with hydrogen halide molecules is formed in the second step. The formation of a complex leads to substantial changes in the region of the stretching vibrations of NH⁺ bonds, and this makes it possible to propose the direct participation of these bonds in complexing. The band of the stretching vibrations of NH⁺ bonds of the acridinium ion has a complex structure that changes markedly as a function of the sort of halogen ion and replacement of hydrogen by deuterium and in the case of complexing with the hydrogen halide. It is proposed that the structure of this band is due to Fermi resonance.