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Chapter – 5 Synthesis and Characterization…..
The compound crystallizes in the Tetragonal crystal class in the space
group I 41 / a with the cell parameters a = 27.7990(6) A°, b = 27.7990(6) A°, c
= 12.1800(8) A°, V = 9412.5(7) A° 3 for Z=16. The structure reveals that the
piperazine ring is in chair conformation. The structure exhibits both inter and
intramolecular hydrogen bonds of the type C-H· · ·O and N-H· · ·N.
A study of torsion angles, asymmetric parameters and least squares
plane calculations reveals that the piperazine ring in the structure is in a chair
conformation with the atoms N8 and N11 deviating 0.2344(26) A° and -
0.2380(24) A° from Cermer and Pople plane defined by the atoms
C9/C10/C12/C13. This is confirmed by the puckering parameters Q = 0.5786(32)
A° θ = 0.36(30)° and Φ = 148.786(5)°. Total puckering amplitude for ten
membered ring O17/C16/C15/C24/C23/C22/C21/C20/C19/C18 is Q = 0.1063(29) A°.
The dihedral angle between the least-squares plane of piperazine ring bridged
via -CH2- to the phenyl ring C1-C6 is 83.89(18)° implying that the phenyl ring is
nearly perpendicular to the plane of the piperazine ring. Piperazine ring and
the coumarin ring bridged via - CH2- group gives a dihedral angle of
87.67(12), which reflect that the piperazine ring is perpendicular to the plane
of the coumarin ring. The dihedral angle between coumarin ring and phenyl
ring bridged via NH group is 65.51(11)°, implies that phenyl ring is equatorial
to the plane of coumarin ring. The two phenyl rings and the coumarin ring are
independently planar. The torsion angle about C6-C7-N8-C9 being -169.34(27)°
and that about C15-C14-C12-C13 being 174.02(23)° show that they reflect -antiperiplanar
and +anti-periplanar conformation, respectively. At the same time
torsion angle about C28-C27-N26-C24 is -166.38(26) indicating -anti-periplanar
conformation. The structure exhibits both inter and intra molecular hydrogen
bonding of the type C-H· · ·O and N-H· · ·N. The intermolecular hydrogen
bond C7-H7A· · ·O17 and C10-H10A· · ·O25 has a length of 3.290(4) A° and
3.460(4) A° and an angle of 130° and 165°, respectively, with symmetry codes
-3/4+y, 5/4-x, -3/4+z and 5/4-y, 3/4+x, -1/4+z respectively. Intramolecular
hydrogen bond N26-H26· · ·N11, has a length of 2.861(3) A° and an angle of
119°. The packing of the molecule along c axis is shown in figure.
Department of Chemistry, Saurashtra University, Rajkot – 360 005 305