Abstract
Imatinib mesylate, 4-(
4-methyl-piperazin-1-ylmethyl)-N-u4-methyl-3-(4-pyridin-3-yl)pyrimidi
ne-2-ylamino)phenyl benzamide methanesulfonate is a therapeutic drug
that is approved for the treatment of chronic myelogeneous leukemia
(CML) and gastrointestinal stromal tumors (GIST). It is known that
imatinib mesylate exists in two polymorphic forms alpha and beta.
However, beta-form is more stable than the alpha-form. In this work, we
present a detailed vibrational spectroscopic investigation of beta-form
by using FT-IR and FT-Raman spectra. These data are supported by quantum
mechanical calculations using DFT employing 6-311G(d,p) basis set, which
allow us to characterize completely the vibrational spectra of this
compound. The FT-IR spectrum of alpha-form has also been discussed. The
importance of hydrogen-bond formation in the molecular packing
arrangements of both forms has been examined with the vibrational shifts
observed due to polymorphic changes. The red shift of the NH stretching
bands in the infrared spectrum from the computed wavenumber indicates
the weakening of the NH bond. The UV-vis spectroscopic studies along
with the HOMO-LUMO analysis of both polymorphs (alpha and beta) were
performed and their chemical activity has been discussed. The TD-DFT
method was used to calculate the electronic absorption spectra in the
gas phase as well as in the solvent environment using IEF-PCM model and
6-31G basis set. Finally, the results obtained complements to the
experimental findings. (C) 2012 Elsevier B.V. All rights reserved.
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