819-826The title molecule
4-benzylidene-2-(2-chloro-phenyl)-5-methyl-2,4-dihydro-pyrazol-3-one, C17H13N2OCl
(I) is synthesized and characterized by IR, NMR and X-ray single crystal
diffraction analysis. Molecular geometry, vibrational wave numbers, frontier
molecular orbitals and Mulliken charges of the title compound have been
calculated using density functional method B3LYP at 6-311g* basis set. Title
compound crystallizes in the monoclinic space group P21/c with
a = 10.343 (3) Å, b = 11.321 (3) Å, <i style="mso-bidi-font-style:
normal">c = 12.486 (4) Å, β = 92.380 (5)°, V = 1460.8 (7) Å3
and Z = 4. The dihedral angles
between the mean plane of chloro phenyl ring, phenyl ring with the mean plane
of pyrazole ring are 65.91(15)° and 21.75(17)°, respectively. After
optimization by DFT method, the twisting of the central pyrazole ring with
chloro phenyl ring and phenyl ring turns out to be 51.96(16)° and 1.26(14)°, respectively.
The drastic differences observed in the dihedral angle calculated after
treating the molecule by DFT method support our observations that molecular
packing is influenced by the collective effect of weak but significant C-H..N,
C-Cl…π, C-H…Cl, C-H…O and π-π interactions in the solid state which are
otherwise lacking in isolated state. The optimized geometric bond lengths, bond
angles and torsional angles obtained by density function theory (DFT) show good
agreement with experimental data. The calculated HOMO and LUMO energies show
that charge transfer occurs within the molecule. Pyrazole oxygen O7 and chloro
phenyl carbon C13 act as bifurcated donor and acceptor in half a dozen
intermolecular interactions, thereby strengthening the molecular packing.
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