Infrared Spectra of Crystalline and Matrix Isolated Pyridine and Pyridine-D5

Abstract

Infrared spectra of pyridine-H5 and pyridine-D5 in the solid state were measured between 4000 and 200 cm− 1. Frequencies and polarization of fundamental absorptions were established for oriented thin films of freshly crystallized samples. Behavior of the bands in polarized light aided in clarifying several assignments. The multiplicity of several of the bands was accounted for by close-lying overtones and combinations. Some of the components of ν26 are due to the existence of appreciable amounts of 13C isotope species clearly observable in a nitrogen matrix at 5°K. For pyridine-D5 a phase transition was clearly observable after several hours of annealing of thin films at about − 60°C, but similar transformation could not be induced in normal pyridine. The infrared crystal data are consistent with an orthorombic factor group established by x-ray analysis with no molecule on any symmetry element of the crystal. Raman spectra of liquid and solid pyridines are also reported.