Low-temperature Fourier transform infrared spectra and hydrogen bonding in polycrystalline L-alanine

M. Rozenberg*, G. Shoham, I. Reva, R. Fausto

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

The 400-4000 cm-1 FTIR spectra of pure NH and isotopically substituted (10 and 90% doped ND/NH) polycrystalline L-alanine were recorded in the temperature range 10-300 K. The observed temperature dependence and isotopic shifts behavior enabled to identify, in the spectra of the doped crystals, three well-separated bands ascribable to either the NH or ND stretching vibrations associated with the three different types of hydrogen bonds existing in the crystal. The observed red shifts of these bands relative to the frequency of a reference "free" NH (or ND) stretching mode were found to correlate well with the H-bond distances found in the crystal and provide an indirect way of estimating the enthalpies associated with each type of H-bond found in the crystal. In the low-frequency deformation and torsional spectral region (below 2000 cm-1), several bands, which were found to be affected by isotopic substitution, were identified as belonging to the NH3+ group. Several bands show splitting at low temperatures, indicating the occurrence of a significant reorganization in the crystal structure, which with all probability results mainly from changes in the proton positions. Finally, the literature assignments of the IR spectra of both crystalline NH3+ and ND3+ L-alanine were revised taking into consideration their temperature dependence and behavior upon deuteration.

Original languageAmerican English
Pages (from-to)3253-3266
Number of pages14
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume59
Issue number14
DOIs
StatePublished - Dec 2003

Bibliographical note

Funding Information:
M.R. gratefully acknowledges financial support from the Israel Ministry for Immigrant Absorption.

Keywords

  • H-bonding
  • L-Alanine crystal
  • Low-temperature FTIR

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