Abstract
Clopidogrel hydrogen sulphate which belongs to a class of medicine
called antiplatelet drugs. Chemically it is methyl
(+)-(S)-alpha-(2-chlorophenyl)-4,5,6,7-tetrahydrothieno 3,2-c
pyridine-5-acetate hydrogen sulphate having the empirical formula
C16H17CINO2S.HSO4 and molecular mass 321.82 g/mol. The present study is
confined to vibrational spectroscopy of the polymorph identified as form
2 of the clopidogrel hydrogen sulphate. The vibrational analysis of
clopidogrel hydrogen sulphate salt (form 2) considering separately the
two counterions has been performed. We also report a theoretical and
experimental study of the molecular conformation and vibrational
dynamics of the independent moieties of the clopidogrel hydrogen
sulphate salt. The equilibrium geometry, harmonic vibrational
frequencies, infrared intensities and activities of Raman scattering
were calculated by ab initio Hartree-Fock and density functional theory
employing B3LYP with complete relaxation in the potential energy surface
using 6-311++G(d,p) basis set. The calculated wavenumbers after a proper
scaling show a very good agreement with the observed values. A complete
vibrational assignment is provided for the observed Raman and infrared
spectra of clopidogrel hydrogen sulphate form 2. (C) 2009 Elsevier B.V.
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