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Vibrational spectra for purine and its 15 N‐ and D‐substituted analogues. Assignment of normal modes from ab initio 3–21G force fields
Author(s) -
Majoube M.,
Henry M.,
Vergoten G.
Publication year - 1994
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250250307
Subject(s) - ab initio , chemistry , tautomer , deuterium , raman spectroscopy , ab initio quantum chemistry methods , normal mode , computational chemistry , hydrogen bond , spectral line , crystallography , molecule , stereochemistry , atomic physics , physics , vibration , organic chemistry , quantum mechanics , astronomy , optics
Abstract Fourier transform (FT) IR and FT‐Raman spectra for purine and its N‐, C 8 ‐ and N‐ and C 8 ‐deuterated analogues and for that 15 N‐substituted on the pyrimidine ring are reported. Experimental data are interpreted by reference to ab initio ‐calculated wavenumbers for normal modes of both N 7 H‐ and N 9 H‐purines. The latter were obtained from normal coordinate analyses carried out on the basis of ab initio 3–21G force fields using the optimized geometry. The effect of hydrogen bonding on the discrepancy between calculated and observed wavenumbers for normal modes was analysed. Considering the solid N 7 H‐purine, the observed 15 N shifts for FT‐IR bands often agree with those calculated for the corresponding normal modes. Several weak bands are tentatively assigned to the N 9 H tautomer, presumably present in small amounts in solution and also in the solid in the case of deuterated purines.