Abstract
In the present study, a systematic investigation on vibrational
properties of captopril (C9H15NO3S) single crystal under pressure is
presented. At first, it is used density functional theory calculation in
order to furnish the assignment of the normal modes as observed through
Raman spectroscopy. In the second part of the paper, it is shown the
Raman spectra of captopril for several pressures up to 6.7 GPa in the
spectral range from 50 to 3300 cm(-1). The study indicates that the
captopril molecules assumes the trans conformation in all pressure range
investigated. The modes appearing in the low wavenumber region of the
spectrum suggest the crystal undergoes a phase transition between 2 and 3 GPa. Additionally, a softening of the C=O bond of both amide and
carboxylic group is observed up to approximately 2.7 GPa and after this
pressure a stiffiness is noted. Finally, is verified a disorder
associated with the CH group during compression.
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