In our earlier researches we have reported the normal vibrations of glycine and its oligomers and cyclic tetraglycine. Structure, infrared spectra, and normal vibration analysis of cyclic diglycine (CDG) have also attracted considerable attention in the literature because of the biological importance of CDG. Although the infrared active Au and Bu fundamental vibrations have been studied extensively, the Raman active Ag and Bg motions have not been reported so far. Recently the Raman active motions have been predicted on the basis of normal coordinate analysis employing Urey-Bradley force field. We thought it worthwhile to record the Raman spectrum of CDG (1) to weigh the applicability of normal coordinate analysis technique in predicting the Ag and Bg fundamental motions of CDG and (2) to substantiate the assignment of these motions on the basis of our observed Raman spectrum.
H. S. Randhawa, S. Harto, and W. Walter, "Laser Raman Spectrum of Cyclic Diglycine," Appl. Spectrosc. 31, 468-469 (1977)