FTIR spectroscopic study of the UV-induced rotamerization of glycine in the low temperature matrices (Kr, Ar, Ne)

Using UV irradiation, the spectral bands of three glycine conformers in the FTIR matrix spectra were separated in the range 4000-180 cm(-1). The absol ute infrared intensities of the spectral bands of these conformers were mea sured. The spectral manifestations of the weak intramolecular H-bonds NH2-O in conformers I, III and the strong H-bond N-H-O-C in conformer II were fo und. The influence of the matrix cage on the efficiency of UV isomerization was demonstrated. The thermodynamic parameters of glycine conformers at T = 358 K were established as: KI-II = 0.13(+/- 0.025), Delta HI-II = 1000 (/- 600) J mol(-1), Delta SI-II = - 14.2(+/- 2) J mol(-1) K-1; and KI-III = 0.16(+/- 0.02), Delta HI-III = 5800(+/- 600) J mol(-1), Delta SI-III = 1(+/ - 2) J mol(-1) K-1. (C) 1999 Elsevier Science B.V. All rights reserved.