1
24
R.N. Singh et al. / Journal of Molecular Structure 1054–1055 (2013) 123–133
are different from the blue shift hydrogen bonds. They are depend
upon the nature of non-conventional hydrogen bond donor and
acceptor involved in the hydrogen bridges and also classified in
three categories such as (i) those in which the nature of hydrogen
bond donor is improper, as a CAH group [19] (ii) the nature of
FT-IR-spectrum was recorded in KBr medium on a Bruker spec-
ꢃ5
trometer. The UV–Visible absorption spectrum of 1 ꢂ 10 M in
DMSO was recorded on ELICO SL-164 spectrophotometer.
3
. Quantum chemical calculations
The quantum chemical calculations- geometry optimization, H
hydrogen bond acceptor is improper, as a C atom or a
iii) both the donor and acceptor are improper groups [20]. DFT/
B3LYP methods and Quantum theory of atoms in molecule
QTAIM) have been used to predict the strength and nature of
p-system
(
1
13
and C NMR chemical shifts, vibrational wavenumbers and UV–
Visible transitions were carried out with Gaussian 03 program
package [23] at B3LYP/6-31G(d,p) basis set. B3LYP functional in-
vokes Becke’s three parameter (local, non local, Hartree–Fock) hy-
brid exchange functional (B3) [24], with Lee–Yang–Parr
correlational functional (LYP) [25]. Further the geometry optimiza-
tion was carried out at B3LYP/6-311+G(d,p) basis set. Topological
parameters were calculated using software AIMALL (Version
(
hydrogen bonding interactions.
There has been growing interest in using organic materials for
non-linear optical (NLO) devices, functioning as second harmonic
generators, frequency converters, electro-optical modulators, etc.
because of the large second order electric susceptibilities of organic
materials. Since the second order electric susceptibility is related to
first hyperpolarizability, the search for organic chromophores with
large first hyperpolarizability is fully justified. The organic com-
pound showing high hyperpolarizability are those containing an
electron-donating group and an electron withdrawing group inter-
acting through a system of conjugated double bond [21]. In case of
sulfonyl hydrazones, the electron withdrawing group is the sulfo-
nyl group. To our knowledge, no theoretical or density functional
theory (DFT) calculations, or detailed infrared spectrum have been
performed on the studied ethyl 3,5-dimethyl-4-[(benzenesulfo-
nyl)-hydrazonoethyl]-1H-pyrrol-2-carboxylate molecule (3).
The Ethyl 3,5-dimethyl-4-acetyl-1H-pyrrol-2-carboxylate is a
suitable precursor for the synthesis of sulfonylhydrazone however
its derivative with benzene sulfonylhydrazide has not been
reported. In order to evaluate sulfonylhydrazone of ethyl 3,5-di-
methyl-4-acetyl-1H-pyrrol-2-carboxylate, the ethyl 3,5-dimethyl-
. .
10 05 04) [26]. Potential energy distribution along internal coordi-
nates is calculated by Gar2ped software [27]. To estimate the en-
thalpy (H) and Gibbs free energy (G) values, thermal corrections
to the enthalpy and Gibbs free energy are added to the calculated
total energies. The global and local electronic parameters have
been calculated by single-point energy calculations over the opti-
mized neutral, cationic and anionic geometries using the unre-
stricted UB3LYP formalism.
4
. Results and discussion
4.1. Thermochemistry
For simplicity, the reactants ethyl 3,5-dimethyl-4-acetyl-1H-
pyrrole-2-carboxylate and benzene sulfonylhydrazide have been
abbreviated as (1) and (2), product ethyl 3,5-dimethyl-4-[(benzene-
sulfonyl)-hydrazonoethyl]-1H-pyrrole-2-carboxylate as (3), and
byproduct water as (4) respectively. Optimized geometries of the
reactants (1, 2), product (3) and by-product (4) involved in chemical
reaction are shown graphically in Scheme 1. The optimized geome-
tries of conformer I and II of (3) are given in Fig. 1. The conformer I
has lower energy then conformer II. They have the energy difference
of 1.0 kcal/mol. The calculated thermodynamic parameters: Enthalpy
4
-[(benzenesulfonyl)-hydrazonoethyl]-1H-pyrrol-2-carboxylate
(
3) was synthesized and characterized. This paper describes the
1
13
synthesis, spectroscopic (( H and ( C NMR, UV–Visible, FT–IR)
analysis, structural evaluation and non-linear optical (NLO) re-
sponse of newly synthesized compound: ethyl 3,5-dimethyl-4-
[
(benzenesulfonyl)-hydrazonoethyl]-1H-pyrrol-2-carboxylate (3).
The dimer formation of (3) has also been evaluated through multi-
ple interactions using quantum chemical calculations and experi-
mental FT-IR spectrum. Furthermore, quantum chemical
calculations have also been performed for the detailed NLO proper-
ties and chemical reactivity of the title compound. The knowledge
of physico-chemical properties and sites of reaction of (3) will pro-
vide a deeper insight.
(H/a.u.), Gibbs free energy (G/a.u.) and Entropy [S (cal/mol-K)] of (1),
(2), (3), (4) and their change for reaction, at 25 °C are listed in Table 1.
For overall uncatalyzed reaction, the calculated positive value of (DH)
shows that the reaction is endothermic. It is to be noticed that net
spontaneity of the chemical reaction is depend upon the Gibbs free
energy change of reaction (DG). For uncatalyzed reaction, the calcu-
lated positive value of ( G) shows that this reaction is non-spontane-
D
2
. Experimental methods and physical measurements
ous at 25 °C. As we know that catalyst plays an important role to
investigate spontaneity of the chemical reaction because catalyst af-
fects the reaction rate, it lowers the activation energy and speed up
the reaction but not equilibrium position. Therefore, this reaction is
carried out in presence of catalyst (polyphorsphoric acid) and on re-
flux temperature 95 °C, overnight. The calculated thermodynamic
parameters: Enthalpy (H/a.u.), Gibbs free energy (G/a.u.) and Entropy
Ethyl 3,5-dimethyl-4-acetyl-1H-pyrrol-2-carboxylate was pre-
pared by an earlier reported method [22]. Benzene sulfonylhydraz-
ide was prepared by stirring the equimolar reaction mixture of
benzene sulfonylchloride and hydrazine hydrate in ethanol. Ethyl
,5-dimethyl-4-acetyl-1H-pyrrole-2-carboxylate (0.100 g, 0.470
mmol) and benzene sulfonylhydrazide (0.081 g, 0.470 mmol) were
dissolved in methanol. The solution of polyphorphoric acid
3
[S(cal/mol-K)] of Monomer, Dimer and their change for Dimerization
reaction, at 25 °C are listed in Supplementary material S Table 1. For
dimerization reaction, the calculated negative value of Gibbs free en-
ergy change (DG) show that the reaction is spontaneous thermody-
namically. At room temperature, the equilibrium constant (Keq) for
dimerization reaction is calculated to be 18.91 i.e. Keq ꢄ 1. There-
fore, reaction is more favoured in the forward direction and confirms
the formation of dimer at room temperature.
(
0.01 ml) was added as catalyst in reaction mixture at room tem-
perature. The reaction mixture was refluxed overnight and comple-
tion of reaction was checked by TLC. After completion of the
reaction, the major portion of solvent was distilled and the obtained
dark reddish colour solid was filtered off. The solid was washed
with saturated solution of sodium bicarbonate and further by
water. The obtained solid product was then recrystallized in meth-
anol to get pure product. Yield: 0.0948 g, 55.50%, M.p. 243 °C. Anal.
calcd. for C17
H
21
N
3
O
4
S: C, 56.18%; H, 5.82%; N, 11.56%; O, 17.61%; S,
4.2. Molecular geometries, conformations and energies
1
8
.82%, obs.: C 56.18%; H 5.79; N 11.58%; O 17.63%; S 8.83%. The H
1
3
and C NMR spectral data was recorded in DMSO-d
6
on Bruker
The optimized geometrical parameters for dimer of ethyl 3,5-di-
DRX-300 spectrometer using TMS as an internal reference. The
methyl-4-[(benzenesulfonyl)-hydrazonoethyl]-1H-pyrrole-2-carbox-