Low temperature FTIR spectra and hydrogen bonds in polycrystalline cytidine

M. Rozenberg*, C. Jung, G. Shoham

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

FTIR spectra of polycrystalline samples of cytidine, pure and containing a small quantity of N(O)H or N(O)D groups (<20%), were measured in KBr pellets from 4000 to 400cm-1 at temperatures from 300 to 20K. For the first time the bands of the narrow isotopically decoupled proton stretching vibration mode (ν1) of OH- and NH- groups were found; their number corresponds to the number of H-bonds in crystal according to structural data. The FTIR spectra at low temperature in the out-of-plane bending ν4 proton mode range (lower than 1000cm-1) of N(O)H groups revealed narrow bands, which correspond to ν1 bands together with several "extra" bands, which are influenced by the isotopic exchange and (or) cooling. All of them have their counterparts in the N(O)D-substance spectrum with an isotopic frequency ratio of 1.30-1.40. The "extra" bands are assigned to the H-bound OH and NH protons, which are disordered and cannot be seen with X-ray crystal structure analysis. The peak positions of both mode bands (expressed as the red shift of ν1 or blue shift of ν4 modes relatively free molecules) were used for the estimation of the energy of different H-bonds using previously established empirical correlations between spectral and thermodynamic parameters of hydrogen bonds. The correlation of the red shift and H-bond length is also confirmed for all five H-bonds of cytidine.

Original languageAmerican English
Pages (from-to)2369-2375
Number of pages7
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume60
Issue number10
DOIs
StatePublished - Aug 2004

Bibliographical note

Funding Information:
M.R. gratefully acknowledges financial support from the Israel Ministry for Immigrant Absorption; this study was supported in part by the German Research Foundation (DFG) to CJ (grant SK35/3.3-5).

Keywords

  • Cytidine crystal
  • FTIR
  • H-bonding
  • Low temperature

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