Vibrational band shape and intensity studies on molecular motions and interactions in condensed phases. Part 3.—Effects of complexation on the molecular dynamics of pyridine

Abstract

The effects of complexation (with ICI) on the shapes of the infrared vibrational bands of pyridine have been investigated. Large changes in the corresponding dipole auto-correlation functions have been interpreted in terms of a large decrease in the rate of orientational motion combined with vibrational broadening due to increased dipole–dipole and transition dipole–transition dipole interactions. Indications that these mechanisms of vibrational relaxation are operative for ‘free’ pyridine has been obtained, and it is shown that on complexation these mechanisms, with some phase-loss broadening, combine to produce a pattern of observed band widths which depends on the intensities, normal coordinates and symmetry properties of the normal modes.