Infrared absorption spectra of single crystals of glycine silver nitrate and monoglycine nitrate

Abstract

The infrared absorption spectra of glycine silver nitrate (GAgNO₃) and glycine nitrate (GHNO₃) show that the glycine group exists completely in the zwitter ion form in the former and in both forms in the latter. The spectrum of GAgNO₃ at liquid air temperature did not reveal any striking change which can be attributed to a freezing of the rapid reorientation of the NH₃⁺ group taking place at higher temperatures. The position of the COO^- stretching frequencies indicate that this group is co-ordinated only weakly to the Ag⁺ ion. The summation frequencies reported by Schroeder, Wier and Lippincott (1962) for AgNO₃ were not observed in the present study on GAgNO₃. It shows however that ferroelectricity in GAgNO₃ is in all probability due to the motion of the Ag+ ion in the oxygen co-ordination polyhedron and is not directly connected with the ordering of the hydrogen bonds below Curie point.