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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. November 2003, Volume 2, Number 11, 757-767 |
Hartree-Fock and Density Functional Studies on the Structure
and Vibrational Frequencies of N-2-(6-Aminopyridine)-N'-arylthioureas
Shridhar P. Gejji and Kaustubh A. Joshi
Internet Electron. J. Mol. Des. 2003, 2, 757-767
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Abstract:
The structure, charge distribution in terms of molecular
electrostatic potentials and frequencies of normal vibrations of
biologically important molecular systems, namely
N-2-(6-aminopyridine)-N'-2-methoxyphenylthiourea 1,
N-2-(6-aminopyridine)-N'-4-chlorophenylthiourea 2,
N-2-(6-aminopyridine)-N'-4-nitrophenylthiourea 3 have been derived.
These structural and vibrational characteristics provide insights
for understanding of molecular interactions. Hartree-Fock and
hybrid density functional methods employing Becke's
three-parameter exchange with Lee, Yang, Parr correlation functional
and with the Perdew Wang functional as well, have been carried
out. Electrostatic potential and its topography have been
analyzed in terms of critical points. Theoretically predicted
structural parameters of these molecules compare well with those
determined from the X-ray diffraction experiments. The
Hartree-Fock calculations predict nonplanar structure around the C-N
bond of the substituted phenylthiourea in 1, 2 and 3. Electrostatic
potential reveals that the intermolecular hydrogen-bonded
network in 3 extends via NO2 group unlike
S···H interactions
present in 1 or 2.The assignments of normal vibrations have
shown that the N3H6 stretching of the thioamide has been
influenced by substitution on the phenyl ring. The present work
reveals that hydrogen bonded network extends through the
C=S···H interactions in 1 and 2
compared to 3 wherein this has
been facilitated through the nitro group. The vibrations of
thioamide group in these molecules are sensitive to the
substituent on the phenyl ring.
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