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Low temperature FTIR spectra and hydrogen bonds in polycrystalline cytidine

Item Type:Article
Title:Low temperature FTIR spectra and hydrogen bonds in polycrystalline cytidine
Creators Name:Rozenberg, M. and Jung, C. and Shoham, G.
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.
Keywords:Cytidine Crystal, FTIR, H-Bonding, Low Temperature
Source:Spectrochimica Acta, A Molecular and Biomolecular Spectroscopy
Publisher:Elsevier / Pergamon Press
Page Range:2369-2375
Date:1 January 2004
Official Publication:https://doi.org/10.1016/j.saa.2003.12.013
PubMed:View item in PubMed

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