Synthesis, computational and spectroscopic analysis on (E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)-3-methyl-2,6-diphenylpiperidine-1-yl)(phenyl)methanone using DFT approach

Article abstract of DOI:10.1016/j.saa.2015.06.037

(E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)-3-methyl-2,6-diphenylpiperidin-1-yl)(phenyl)methanone [EPHDPM] and its derivatives were synthesized and characterized by FT-IR, ¹H NMR, ¹³C NMR and elemental analysis. The target compound [EPHDPM] was computed using density functional theory (DFT) method. The ground-state molecular geometry and vibrational frequencies were calculated by using B3LYP/6-31G (d,p) level of theory. The experimentally observed FT-IR and FT-Raman bands were assigned to different normal modes of the molecule. The stability and charge delocalization of the molecule were also studied by natural bond orbital (NBO) analysis. The HOMO-LUMO energies describe the charge transfer takes place within the molecule. Molecular electrostatic potential has been analyzed. The reported EPHDPM molecule used as a potential NLO material since it has high μβ₀ value. Thermodynamic parameter like entropy and enthalpy are calculated and these values are increased with increasing the temperature due to the enhancement of vibrational intensities.

Full text of DOI:10.1016/j.saa.2015.06.037

Accepted Manuscript
Synthesis, computational and spectroscopic analysis on (E)-(4-(2-(ben-
zo[d]thiazol-2-yl)hydrazono)methyl-2,6-diphenylpiperidine-1-yl)(phe-
nyl)methanone using DFT Approach
D. Rajaraman, A. Kamaraj, G. Sundararajan, H. Saleem, K. Krishnasamy
PII:
S1386-1425(15)00752-0
http://dx.doi.org/10.1016/j.saa.2015.06.037
SAA 13807
DOI:
Reference:
Spectrochimica Acta Part A: Molecular and Biomo-
lecular Spectroscopy
To appear in:
Received Date:
Revised Date:
Accepted Date:
1 November 2014
8 June 2015
12 June 2015
Please cite this article as: D. Rajaraman, A. Kamaraj, G. Sundararajan, H. Saleem, K. Krishnasamy, Synthesis,
computational and spectroscopic analysis on (E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)methyl-2,6-
diphenylpiperidine-1-yl)(phenyl)methanone using DFT Approach, Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy (2015), doi: http://dx.doi.org/10.1016/j.saa.2015.06.037
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Synthesis, computational and spectroscopic analysis on (E)-(4-(2-
(benzo[d]thiazol-2-yl)hydrazono)methyl-2,6-diphenylpiperidine-1-
yl)(phenyl)methanone using DFT Approach.
D. Rajaramana, A. Kamaraja, G. Sundararajana, H. Saleemb, K. Krishnasamya*
aDepartment of Chemistry, Annamalai University, Annamalainagar, 608 002, Tamilnadu, India.
bDepartment of Physics, Annamalai University, Annamalainagar, 608 002, Tamilnadu, India.
ABSTRACT
(E)-(4-(2-(benzo[d]thiazol-2yl)hydrazono)methyl-2,6-diphenylpiperidin-1-
yl)(phenyl)methanone [EPHDPM] and its derivatives were synthesized and characterized by FT-IR,
13
1H NMR, C NMR and elemental analysis. The target compound [EPHDPM] was computed using
Density Functional Theory (DFT) method. The ground-state molecular geometry and vibrational
frequencies were calculated by using B3LYP/6-31G (d, p) level of theory. The experimentally
observed FT-IR and FT-Raman bands were assigned to different normal modes of the molecule. The
stability and charge delocalization of the molecule were also studied by natural bond orbital (NBO)
analysis. The HOMO-LUMO energies describe the charge transfer takes place within the molecule.
Molecular electrostatic potential has been analyzed. The reported EPHDPM molecule used as a
potential NLO material since it has high µβ0 value. Thermodynamic parameter like entropy and
enthalpy are calculated and these values are increased with increasing the temperature due to the
enhancement of vibrational intensities.
Keywords: FT-IR, FT-Raman, TED, NBO, HOMO-LUMO and EPHDPM.
Corresponding Author contact No; +91-9942547856
Email: krishnasamybala56@gmail.com

Introduction
Piperidine heterocyclic plays an important role in the field of medicinal chemistry. Several
2,6-disubstituted derivatives of this class have been found to possess useful biological activities such
as herbicidal, insecticidal, fungicidal, bactericidal, antiinflammatory, antihistaminic, hypotensive,
anticancer, CNS stimulant and depressant and nerve activities [1-8]. The biological activities of
piperidones are found to be excellent if 2- and/or 6-positions are occupied by aryl groups [9]. In the
present work 3-methyl-2, 6-diphenylpiperidin-4-one was synthesized by Mannich reaction
(condensation) using ethyl methyl ketone, benzaldehyde and ammonium acetate. Finally (E)-(4-(2-
(benzo[d]thiazol-2-yl)hydrazono)methyl-2,6-diphenylpiperidine-1-yl)(phenyl)methanone
was
synthesized using N-benzoyldiphenylpiperidine-4-one and 2-hydrazinobenzothiozole. Molecular
geometry critically influences the biological activities. Apart from other organic compounds,
hydrazone derivatives have antimicrobial, antiviral, antitubercular, anticonvulsant and anti-
inflammatory effects in the field of medicine [10-17]. Quantitative structure activity relationship
(QSAR) studies, surface area and molecular volume are found to play an important role in the
overall activity of the biologically active molecule [18]. Vibrational spectroscopy is a valuable tool
for the elucidation of molecular structure and gives a dynamical image of the molecule. Vibrational
spectroscopy has contributed appreciably to the growth of polymer chemistry, catalysis and speedy
reaction dynamics etc [19]. The present research work mainly focused on the synthesis of (E)-(4-(2-
(benzo[d]thiazol-2-yl)hydrazono)methyl-2,6-diphenylpiperidine-1-yl)(phenyl)methanone and its FT-
IR, FT-Raman vibrational spectra characterization. To support our experimental investigation and
the theoretical calculation such as conformational, vibrational analysis were studied using B3LYP/6-
31G (d, p) level of theory [20]. For the accurate prediction of vibrational assignments the total
energy distribution analysis was carried out. In addition the intra-molecular charge transfer, non-

linear optical activity, frontier molecular orbital analysis, thermodynamic behavior and molecular
electrostatic potential of the title molecule have been also studied.
Experimental
Synthesis of 2-hydrazinobenzothiazole
Equimolar solution of 2-mercaptobenzothiazole (0.01mol) and hydrazine hydrate (0.01mol) in
methanol (20 mL) was refluxed on a steam bath for about 10 hrs. The obtained filtrate was washed
with ice water. The product was dried and recrystallized from ethanol to yield the pure compound
(yield 60%, m.p. 201-205 ˚C).
Synthesis of N-benzoyl-2,6-diarylpiperidine-4-one
Piperdine-4-one (0.01 mol) and triethylamine (0.01 mol) in 30 mL of dry benzene, benzoyl
chloride (0.01 mol) in 20 mL of benzene was added dropwise through the separating funnel for
about half an hour. Stirring was continued with (0˚C) a magnetic stirrer. After the completion of the
reaction, it was poured into water and extracted with diethyl ether in three 50 mL portions. The
combined ether extract was then washed well with 3% sodium bicarbonate solution and dried over
anhydrous sodium sulphate. This upon evaporation and subsequent recrystallization in distilled
ethanol furnished the title compound in pure form with good yield.
Synthesis
of
(z)-(4-(2-(benzo[d]thizol-2-yl)hydrazano)-3-methyl-2,6-diphenylpiperidin-1-
yl)(phenyl)methanone [EPHDPM]
A
Mixture of N-benzoyl-2, 6-diarylpiperidin-4-one (0.01 mol) in methanol and
2-hydrazinobenzothizol (HBT) (0.01 mol) was added with constant stirring and the reaction mixture
was refluxed on a water bath. The completion of the reaction was monitored using TLC (Thin layer

Chromatography). After cooling the product was filtered and then washed with water. The product
was purified by column chromatography using 20% ethyl acetate in hexane. The schematic
representation of the target compound is given in scheme 1.
FT-IR and FT-Raman measurement
The FT-IR spectrum of the synthesized EPHDPM was measured in the 4000-400 cm-1 region
using on AVATAR-330 FT-IR spectrophotometer (Thermo Nicolet). FT-IR spectrum was recorded
in Department of Chemistry, Annamalai University, Annamalainagar. The FT-Raman spectrum of
the title compound was recorded on BRUKER: RFS27 spectrometer operating at laser 100 mW in
the spectral range of 4000-50 cm-1. FT-Raman spectral measurements were carried out from
Sophisticated Analytical Instrument Facility (SAIF), Indian Institute of Technology (IIT), Chennai.
Computational details
The density functional theory (DFT/B3LYP) at the 6-31G (d, p) was used to calculate the
properties, such as FT-IR, FT-Raman stretching vibrations, optimized geometries, vibrational
frequencies, NBO analysis, HOMO-LUMO and thermodynamic properties, dipole moment,
hyperpolarizability of the title molecule. All the calculations were performed using Gaussian 03W
program package [21] with the default convergence criteria without any constraint on the geometry
[22]. The optimized structural parameters were used in the vibrational frequency calculations at the
DFT level to characterize all minima. The vibrational modes were assigned on the basis of TED
(Total Energy Distribution) analysis using SQM program [23]. It should be noted that Gaussion
03W package able to calculate the Raman activity. The Raman activities were transformed into
Raman intensities using Raint program [24] by the expression:
4
Ii = 10-12 (ʋ0- ʋi) / ʋi . s
(1)

Where Ii is the Raman intensity, S is the Raman scattering activities, ʋi is wave number of the normal
modes and ʋ0 denotes the wave number of excitation laser [25].
Results and Discussion
Molecular geometry
The chair conformer of piperidine molecule is the most stable conformer and it has two possible
chair conformations, which differ in the axial (A) or equatorial (E) positions of the N–benzoyl group
[26–28]. The optimized structure of EBHDPM is shown in Fig. 1. The selected geometrical
parameters such as bond length, bond angle and dihedral angles are presented in Table 1
(Supplementary material). The target compound looks like to exist in chair conformation with the
dihedral angle of N6-C1-C2-C3 (-52°) and N6-C5-C4-C3 (52°). In the present work, the C1-N6
(1.48 Å), C5-N6 (1.49 Å) bond length is higher compared to N-benzoylpiperidine-4-one [(C1-N6
(1.31 Å), C5-N6 (1.31 Å)] and C27-N6 (1.38Å) bond lengths are less compared to corresponding
bond length in N-benzoylpiperidine-4-one (1.46 Å) but C27-O28 (1.22 Å) and C26-O27(1.25 Å)
bond length is almost similar due to the conjugation double bond present in the carbonyl group and
also the longest bond distance attributes the pure single bond character [29]. The 2C-3C (1.50 Å),
5C-6C (1.56 Å) bond length is higher when compared to N-benzoylpiperidine-4-one due to presence
of C=N in C3 carbon atom. The intramolecular hydrogen bonding interaction are obtained
(C27=O28…H29) with bond angle 83.10Å.
Vibrational assignments
The molecule has 66 atoms and hence it shows 192 normal modes of vibrations of EPHDPM
are distributed into the irreducible representations as 65 stretching vibration and 129 in-plane
bending vibration and 63 out-of-plane bending vibrations. All vibrations are active in both IR
absorption and Raman scattering. The fundamental vibrational wave numbers of EPHDPM was

calculated by B3LYP/6-31G (d, p) level of theory. The selected simulated IR, Raman intensities and
experimental FT-IR, FT-Raman frequencies are listed in Table 1. The difference between
experimental and computed wave number were corrected by introducing a scaled field [30] or
directly scaling the calculated wave number with the proper factor [31]. Experimental FT-IR and
calculated IR spectra are shown in Fig. 2. The experimental FT-Raman and simulated Raman spectra
are shown in Fig. 3. The vibrational assignments were carried out using total energy distribution
(TED) calculation method equipped with SQM program. To bring the theoretical values closer to
experimental values, we used the scale factor 0.9068 [32].
NH vibrations
The N–H stretching vibration appears strongly in the region of 3500–3300 cm-1. In this study, the
frequency was observed as strong band in both FT-IR and FT-Raman, where the frequencies were
attributed to 3416 cm-1 and 3402 cm-1 respectively. The corresponding theoretical N–H frequency is
about 3424 cm-1 (mode no 192) and these values are almost equal.
C=O and C=N vibrations
The carbonyl C=O stretching vibration is expected to occur in the region 1680–1715 cm-1 [33,
34]. In the present study, the C=O stretching appeared as strong band at 1632, 1643 cm-1 in FT-IR
and FT-Raman respectively and the same band was computed about 1662 cm-1 (mode no: 164).
Both observed and calculated values are coincides well with each other. The TED analysis shows
about 72% of contribution. The intensity of the carbonyl group can increased due to the conjugation
and formation of hydrogen bond. The above assignments agree well with the value available in the
literature [35, 36]. The C=N stretching frequency is observed at 1594cm-1 and 1601.12cm-1 with a
very strong band in FT-IR and FT-Raman respectively and its theoretical frequency is observed 1602

cm-1 and 1664 cm-1 (mode nos:162,163). The experimental and theoretical value for C=N band
coincides well with literature [37].
C-N and C-S vibration
The identification of C-N vibration is very difficult tasks since mixing of several bands are
possible in this region. However with the help of theoretical calculation B3LYP 6-31G (d,p) the C-N
stretching vibrations are calculated. In the present investigation the calculated C-N stretching
vibration appeared at 1282, 1312 and 1343 cm-1 with the modes: 124, 136 and 138 respectively. The
C-S bending vibrational frequency is observed at 1019 &1003cm-1 in FT-IR and FT-Raman
respectively and its theoretical frequency is about 964, 1090 cm-1 (mode nos: 91, 108).
Methyl and methylene group vibrations
Methyl groups are generally referred to as electron donating substituent in the aromatic ring
system [38]. The title molecule possesses methyl (CH3) and methylene (CH2) groups. Methyl group
symmetric stretching vibration is observed at 2920 cm-1 (strong bond) in FT-IR and 2935cm-1 (weak
band) in FT-Raman are in agreement with the theoretical value of 2904 cm-1 (mode no: 165) with the
TED value is 78%. The methyl group asymmetric stretching vibration is calculated at 2981-2951 cm-
1
(mode nos: 169 and 168), which is agreed well with recorded value of 2964 cm-1 by FT-Raman
spectrum and also possesses considerable TED value. The asymmetric and symmetric CH2
stretching vibrations are normally appear in the region 3100–2900 cm-1 [39]. According to the
literature [40], symmetric CH2 stretching vibrations are appeared at 2843cm-1 as a weak band in FT-
IR with the scaled harmonic frequency 2939 cm-1 (mode no: 167) and its TED value is appeared
about 81%.
In aromatic compounds the αC-H, βC-H and γC-H modes are appeared in the range of 3000–3100,
1000–1300 and 750–1000 cm-1 respectively [41-44]. In our present study the simulated IR and

Raman C-H stretching vibrational frequencies appeared in the region of 3010–3146 cm-1 (mode nos:
170–191). The observed frequencies showed at 3200, 3063, 2964, 2920, 2843 and 2838 cm-1 (FT-
IR) and 3260, 3063, 2935, 2877, 2729, 2625 and 2590 cm-1 (FT-Raman) for C-H stretching
vibrations. The C-H in-plane bending vibrations appeared in the range 1005–1032 cm-1 (mode nos:
95–105) and their corresponding experimental frequency observed at 1024 cm-1 (FT-IR) and 1003
cm-1 (FT-Raman) are in consistent with computed values. The resulting vibrational wave numbers,
IR intensities, Raman scattering activities and experimental FT-IR and FT-Raman frequencies for
the optimized structure are listed in Table 2 (Supplementary material).
NBO Analysis
The hyperconjugation may be given as stabilizing effect that arises from an overlap between an
occupied orbital with another neighboring electron deficient orbital when these orbitals are properly
oriented. This non-covalent bonding–antibonding interaction can be quantitatively described in
terms of the NBO analysis, which is expressed by means of the second-order perturbation interaction
energy E(2) [45–48]. This energy represents the estimation of the off-diagonal NBO Fock matrix
elements and it can be deduced from the second-order perturbation approach [49].
E(2) = ∆Eij(2)= qi (F(i, j)2 /ϵj-ϵi,
Where qi is the donor orbital occupancy, εi and εj are diagonal elements (orbital energies)
and F(i, j) is off diagonal NBO Fock matrix elements. This equation is used to determine the energy
of hyperconjugative interactions (stabilization energy). Especially the amount of energy transfer
from bonding orbital to anti-bonding orbital and the stabilization energy E(2) is associated with the
extent hyperconjugative interaction. The most important interaction energies of charge transfer is

mainly by the orbital overlap between n (LPS44) and π*(C42-N43). The loan pair of electron in
nitrogen (LP(1)N40) transfer its electron to antibonding orbital C3-N8/C42-N43 with stabilization
energy 122.84 and 209.20 kJ/mol, respectively. These bonds orbital which results intramolecular
charge transfer (ICT) causing stabilization of the system. But in the case of N-Benzoylpiperidine-4-
one there is no (n- π*) interaction. The LPO28→ N6-C27/C27-C31 are obtained as 102.22 and
80.29kJ/mol, But in the case of N-benzoylpiperidine-4-one the energy transfer from LPO27→N6-
C26 are obtained as 93.09kJ/mol with electron density 1.80e. The π-π* electron transitions are more
favorably operated between πC34-C36 to π*C30-C32 antibonding orbital which is stabilized by
90kJ/mol. But N-benzoylpiperidine-4-one (without the benzothiazole moiety) revealed that the π-π*
charge transfer takes place from π C15-C17 to π* C19-C21 antibonding orbital with stabilization
energy is 95.46kJ/mol. The decrease in hyperconjugative interaction energies are caused with
substituent effect. These interactions are observed as an increase in electron density (ED) in C-C
anti-bonding orbital that weaken their respective bonds [50]. In NBO analysis large E(2) values
shows the intensive interaction between electron-donors and electron acceptor interaction. The
possible intensive interactions are given in Table 3 (Supplementary material).
Thermodynamic properties
The calculations were conceded out via the ideal gas approximation at constant pressure of
1atm. Scale factors have been suggested [51, 52] for an precise calculation in decisive the Zero-Point
Vibration Energies (ZPVE), Entropy, Translational, Rotational, Vibrational components are used to
calculate the entropy and free energy values are given in Table 2. The gas molecules will be spread
into a superior numbers of energy levels. At elevated temperatures, the vibrational populations will
be dispersed in a larger number of vibrational levels contributing to increase the entropy. At low
temperatures, the translational energy levels donate strongly to the behavior of entropy. Therefore,

rotational and vibrational populations are spread in a few low energy levels [53]. The
thermodynamic quantities such as, total enthalpy (H) and entropy (S) for various ranges (100–1000
K) of temperature are calculated and these results are presented in the Table 4 (Supplementary
material). It can be observed that the thermodynamic parameters are increasing with temperature
ranging from 100 to 1000 K due to the fact that the vibrational intensities increase with temperature
[54]. The relation between entropy and enthalpy with temperature are shown in Fig. 4.
Molecular electrostatic potential
Molecular electrostatic potential provides a visual method to understand the relative polarity of
the molecule. MEP is a valuable tool in predicting and analyzing the molecular interactions such as
Drug – receptor and enzyme – substrate interactions. MEP is very helpful for the qualitative
elucidation of elecrophilic and nucleophilic reactions for the study of biological discovery process
and hydrogen bonding interactions [55]. An electron density iso-surface mapped with electrostatic
potential surface depicts the size, shape, charge density and site of chemical reactivity of the
molecule. The different values of the electrostatic potential at the surface are represented with
different colors (the red color surfaces with negative MEP are due to high electron density and the
blue color surfaces correspond to areas of lowest electron density). MEP map with electron contour
graph for the EPHDPM is shown (in Fig. 5.) with color range from -9.75e-2 (deepest red) to +9.75e-
2 (deepest blue). The MEP diagram shows the negative potential site is situated over benzothiazole
containing phenyl group except hydrogen atom and the positive potential sites are around the
hydrogen atoms. The phenyl ring regions are neutral as represented by green color. These sites give
information about the region from where the molecule can have intermolecular interactions [56].

HOMO–LUMO analysis
The analysis of the wave function indicates that the electron absorption corresponds to the transition
from the ground state to the first excited state and is mainly described by one electron-excitation
from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital
(LUMO) [57]. LUMO is an electron acceptor represents the ability to obtain an electron and HOMO
is an electron donor represents the ability to donate electron [58]. The energy gap for EBHDPM was
calculated using B3LYP/6-31G (d, p) level of theory. The energy gap between the HOMO and
LUMO molecular orbitals determine the chemical stability and electrical transport properties of the
molecule. The red and green colors of the molecular orbital plot represent the positive and negative
phase respectively. The HOMO shows the charge density localized over the benzothiozole ring
except hydrogens and the LUMO part is located on N-benzoyl phenyl ring. This observation
indicated that the charge transfer takes place from benzothiozole moiety (HOMO) to N-benzoyl
phenyl ring (LUMO). The energy difference between the HOMO and LUMO is about 4.27eV. The
low energy gap value represents the high reactivity of the molecule in chemical reactions [59].
Further the HOMO-LUMO analysis of N-benzoylpiperidine-4-one shows that the HOMO and
LUMO orbitals are separated with the energy gap of 2.53eV. The smaller band gap energy increases
the stability of the molecule. The frontier molecular orbital of EBHDPM (HOMO–LUMO) are
shown in Fig. 6 and N-benzoylpiperidine-4-one (HOMO–LUMO) are shown in Fig. 1.
(Supplementary material).
HOMO energy = -5.42eV
LUMO energy = -1.14eV
Energy gap
=
4.27eV

Mulliken and NBO charge analyses
The calculation of atomic charges plays an important role in the application of quantum mechanical
calculations to molecular systems [60]. The total atomic charge values are obtained by Mulliken
population analysis with optimized geometry and natural charges are obtained by natural bond
orbital analysis (NBO) [61] and data is listed in Table 3. As seen in from Table 3, the two methods
predict the same tendencies. The C27, C3 and C42 atoms has bigger positive atomic charges
(0.53(M); 0.66(NBO)), (0.39(M); 0.40(NBO)) and (0.36(M); 0.33(NBO)), than the other carbon
atoms. This is due to the electronegative atoms such as oxygen and nitrogen attached to carbon
atoms. The S44 atom (0.31(M); 0.41(NBO)) has the positive. Results from Table 3, oxygen and
nitrogen atoms in title compounds have more negative charges than the other atoms. Mulliken and
NBO Population Methods are predicting the reactive sites present in the title compound. According
to these result, NBO’s net charges are slightly longer than Mulliken charges, which is also supported
by MEP analysis.
Non linear optics
The hyperpolarizability (β0), dipole moment (µ) and polarizability (α0) values are calculated
using B3LYP/6-31G (d,p) on the basis of the finite-field approach. The calculated polarizability and
hyperpolarizability are reported in electrostatic units (e.s.u) and the values are presented in Table 4.
The large value of hyperpolarizability (β0) which is a function of the non-linear optical activity of the
molecular system is associated with the intra-molecular charge transfer, resulting from the electron
cloud movement through conjugated framework from electron donor to electron acceptor groups.
The smaller band gap energy may increase the NLO properties of the molecule. The physical

properties of these conjugated molecules are governed by the high degree of electronic charge
delocalization along the charge transfer axis and by the low band gaps. The calculated
hyperpolarizability value of EPHDPM (2.250x10-30esu) is greater than the N-benzoylpiperidine-4-
one (1.744 x10-30esu).
So, we concluded that the title molecule has better nonlinear optical properties. The
hyperpolarizability and dipole moment value of N- benzoylpiperidine -4-one is shown in Table 3
(Supplementary material).
(E)-(4-(2-(benzo[d]thiazol-2yl)hydrazono)methyl-2,6-diphenylpiperidin-1yl)(phenyl)methanone
derivatives (1)
White solid: m.p. 168-170˚C and yield 68 %. IR (KBr) (cm-1): 3063, 2964, 2920 and 2843 (C-H
1
stretching); and 1632 (N-C =O stretching); 1594 (C=N stretching); and 3310 (NH stretching). H
NMR (400 MHZ-CDCl3 ppm): δ 0.92 (d, 3H, CH3, J= 4HZ), 2.00 (t, 1H, H5a, J=1.8HZ); 2.23 (s, 1H,
H3a), 3.52 (d, 2H, H2a, H5e, J=2HZ), 3.85 (d, 1H, H6a, J=3.5HZ) 6.95 (s, 1H, hydrazine NH), 7.02-7.87
(m, 17H, aromatic protons).13 C NMR ( 100 MHZ-CDCl3 ppm): δ 170.49 (CO), 165.11 (C=N),
157.90 (C-4, C=N), 118.06-137.02 (aromatic and ipso carbon), 77.04 (C-2), 60.07 (C-6), 37.02 (C-
3), 29.72 (C-5), 14.22 (CH3). Elemental analysis: cal. C-74.39, H5.46, N-10.84, O-3.10,S-6.21 Exp:
C-73.12, H-5.03, N-9.63,O-2.89, S-6.05
(E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)-3-methyl-2,6-di-p-tolylpiperidin-1-yl)(phenyl)methanone
(2)
White solid: m.p. 169-172˚C and yield 64%. IR (KBr) (cm-1): 2920, 2849 (C-H stretching) and 1632
(N-C =O stretching); 1605 (C=N stretching); and 3310 (NH stretching); 1H NMR (400 MHZ-CDCl3
ppm): δ 1.05 (d, 1H, CH3, J=2HZ), 1.27 (m, 6H, PhCH3), 2.19 (t, 1H, H5a, J=2.6HZ), 2.06 (s, 1H, 3a),
3.20 (m, 2H, H2a, H5e ), 4.13 (q, 1H, H6a), 6.90 (s, 1H, NH), 6.92-7.66 (m, 17H, aromatic proton).

13C NMR (100 MHZ-CDCl3 ppm): δ 169.08, (CO), 168.9 (C=N), 158.5 ((C-4, C=N), 121.35-137.08
(aromatic and ipso carbon), 77.03 (C-2), 60.42 (C-6), 29.71 (Ph-CH3), 21.09 (C-3), 20.99 (C-5),
14.65 (CH3). Elemental analysis: cal. C-74.97, H-5.92, N-10.29, O-2.94, S-5.89. Exp: C-73.89, H-
5.24, N-9.86, O-2.13, S-5.32.
(E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)-2,6-bis(4-methoxyphenyl)-3-methylpiperidin-1-
yl)(phenyl)methanone (3)
White solid: m.p. 165-168˚C and yield 69%. IR (KBr) (cm-1): 2964, 2920, 2849 and 2832 (C-H
stretching) and 1616 (N-C=O stretching); 1556 (C=N stretching); and 3420 (NH stretching); 1H
NMR (400 MHZ-CDCl3 ppm): δ 0.91 (d, 1H, CH3, J=2.4HZ), 2.13 (t,1H, H5a,J=24HZ), 2.47 (s, 1H,
H3a), 2.92 (d, 2H, H2a, H5e,J=8HZ), 3.73 (m, 6H, OCH3), 4.14 (d, 1H, H6a, J=1.8HZ), 6.62 (s, 1H,
13
hydrazine NH), 6.75-7.56 (m, 17H, aromatic proton). C NMR (100 MHZ-CDCl3 ppm): δ 171.49
(CO), 168.16 (C=N), 159.09 (C-4, C=N), 113.37 -135.36 (aromatic and ipso carbon), 77.0 3 (C-2),
68.66 (C-6), 36.53 (C-3), 29.72 (C-5), 21.08(CH3). Elemental analysis: cal. C-70.81, H-5.59, N-9.71,
O-8, 32, S-5.56.Exp: C-70.12, H-5.03, N-9.23, O-8.00, S - 5.05.
(E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono) -2,6-bis (4-fluorophenyl) -3-methyl piperidin-
1yl)(phenyl)methanone (4)
White solid: m.p. 172-175˚C and yield 64%. IR (KBr) (cm-1): 3020, 2949, 2836, 2815 and 2854 (C-
H stretching); and 1710 (N-C=O stretching); 1585 (C=Nstretching) and 3200 (NH stretching); 1H
NMR (400 MHZ-CDCl3 ppm): δ 1.13 (d, 1H, CH3,J= 2HZ), 1.90 (s, IH, H5a), 2.89 (t, 1H,
H3a,J=1.5HZ), 3.23 (t, 1H, H5e,J=2HZ), 3.71 (d, 1H. H2a,J=1.2HZ), 3.8 (d, 1H, H6a,J=3HZ), 6.7 (s, 1H,
13
hydrazine NH), 6.79-7.64 (m, 17H, aromatic protons). C NMR (100 MHZ-CDCl3 ppm): δ 173.49
(ph-CO), 169.11 (C=N), 162.90 (C-4, C=N), 114.79-136.75 (aromatic and ipso carbon), 77.30 (C-

2), 77.05 (C-6), 76.79 (C-3), 53.45 (C-5), 29.88 (CH3). Elemental analysis: cal. C-69.55, H-4.74, F-
6.88, N-10.14, O-2.90, S-5.80. Exp: C-68.03, H-4.12, F-6.73, N-9.89, O-2.30, S - 5.31.
(E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)-2,6-bis(4-chlorophenyl)-3-methylpiperidin-1-
yl)(phenyl)methanone (5)
White solid: m.p. 174-176˚C and yield63%. IR (KBr) (cm-1): 3020, 2949, 2836, 2815 and 2854 (C-
H stretching) and 1710 (N-C=O stretching); 1585 (C=N stretching); and 3210 (NH stretching); 1H
NMR (400 MHZ-CDCl3 ppm): δ 0.84 (d, 1H, CH3,J=0.8HZ), 2.06 (t, 1H, H5a,J=0.4HZ), 2.61 (m,1H,
H3a), 3.52 (d, 2H, H2a,H5e,J=1.2HZ), 3.77 (d, 1H, H6a,J=1.6HZ), 6.85 (s, 1H, hydrazine NH), 7.12-
7.62 (m, 17H, aromatic proton).13C NMR (100 MHZ-CDCl3 ppm): δ 170.28 (CO), 155.10 (C=N),
149.62 (C-4, C=N), 118.00-141.33 (aromatic and ipso carbon), 68.34 (C-2) 59.83 (C-6), 45.01 (C-
3), 36.73 (C-5), 12.07 CH3). Elemental analysis: cal. C-65.64, H-4.48, Cl-12.11, N-9.57, O-2.73, S-
5.48. Exp: C-64.20, H-4.41, Cl-12.01,
N-9.01, O-2.32, S - 5.04.
(E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)-2,6-bis(4-brmophenyl)-3-methylpiperidin-1-
yl)(phenyl)methanone (6)
White solid: m.p. 167-171˚C and yield 70%. IR (KBr) (cm-1): 3052 2969, 2936, 2915 and 2854 (C-
1
H stretching) and 1720 (N-C=O stretching); 1605(C=Nstretching) and 3200 (NH stretching); H
NMR (400 MHZ-CDCl3 ppm): δ 0.83 (d, 1H, CH3,J=1.4HZ), 1.30 (t, 1H, H5a,J=2HZ), 2.61 (m, 1H,
H3a), 3.59 (d, 2H, H2a, H5e,J=2HZ), 4.04 ((d, 1H, H6a,J=4HZ), 6.85 (s, 1H, hydrazine NH), 7.26-8.12
(m, 17H, aromatic proton). 13C NMR ( 100 MHZ-CDCl3 ppm): δ 13C NMR (100 MHZ-CDCl3 ppm):
δ 172.00 (CO), 169.80 (C=N), 158.5 (C-4, C=N), 113.00-150.51 (aromatic and ipso carbon), 61.50
(C-2) 58.3(C-6), 45.01 (C-3), 37.20 (C-5) 12.09 (CH3). Elemental analysis: cal. C-56.99, H-3.89, Br-
23.69, N-8.31, O-2.37, S-4.75. Exp: C-56.10, H-2.99, Br-23.31, N-7.43, O-2.12, S – 4.32

Conclusion
In the present study, the detailed vibrational spectral analysis of the EPHDPM was performed
by combining the experimental and theoretical information using density functional theory. The
DFT/B3LYP method with 6-31G (d, p) basis set showed better agreement with the experimental
spectrum. The NBO results reflect the charge transfer is mainly by the orbital overlap between n
(LPS44) and π*(C42-N43) bond orbital which results intramolecular charge transfer (ICT) causing
stabilization of the system. Molecular electrostatic potential studies revealed that the oxygen atom
will be the most reactive site for electrophilic attack and the hydrogen atom will be the reactive site
for nucleophilic attack. HOMO–LUMO gap with 4.27eV indicates that the title compound has a
good chemical stability. Atomic charges on the various atoms of EPHDPM obtained by Mulliken’s
population analysis. It was also observed that there is a large accumulation of positive charge on
H41 atom and large accumulation of negative charge on N43 in the title molecule. Furthermore, the
hyperpolarizability and total dipole moment properties of the molecule show that the title molecule
is a better nonlinear optical property compared to N-Benzoylpiperidine-4-one. The geometry of (E)-
(4-(2-(benzo[d]thiazol-2-yl)hydrazono)methyl-2,6-diphenylpiperidine-1-yl)(phenyl)methanone
derivatives are largely exist in chair conformations.
Acknowledgements
The authors K. Krishnasamy and D. Rajaraman thank the university grant commission for the
financial support (major research project, F. NO: 42-342/2013) of this research work.

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Figure Captions
Table 1
Vibrational wave numbers obtain for EPHDPM at B3LYP6-31G (d,p) level of
theory
Table 2
Table 3
Thermodynamic parameters of EPHDPM
Selected Mulliken and NBO charges of EPHDPM
Table 4
The molecular electric dipole moments (µ), Polarizability (α0) and
hyperpolarizability (β0) values of target compound
Scheme 1
Synthesis of Novel (E)-(4-(2-(benzo[d]thiazol-2-yl)hydrazono)methyl-2,6-
diphenylpiperidin-1-yl) (phenyl)methanone
Figure 1
Figure 2
The optimized structure and numbering scheme of EPHDPM
Experimental FT-IR (a) and theoretical IR (b) spectrum of EPHDPM
Figure 3
Experimental FT-Raman (a) and Theoretical Raman (b) spectrum of EPHDPM
Figure 4
Figure 5
Figure 6
Variation of Entropy and Enthalpy with temperature for EPHDPM
Molecular electrostatic potential for EPHDPM
HOMO-LUMO Energy diagram of EPHDPM

SCHEME-1
Compounds
1
X
H
R
C6H5CO

2
3
4
5
6
CH3 C6H5CO
OCH3 C6H5CO
F
C6H5CO
C6H5CO
C6H5CO
Cl
Br

Fig. 1. The optimized structure and numbering scheme of EPHDPM

IR/B3LYP/6-31G(d,p)
0
10
20
30
40
50
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber (cm-1)
Fig. 2. Combined experimental (FT-IR) and theoretical (IR) spectra of EPHDPM

0.6
0.5
0.4
0.3
0.2
0.1
0.0
RAMAN/B3LYP/6-31G(d,p)
4000
3500
3000
2500
2000
1500
1000
500
0
-1
Wavenumber (cm )
Fig. 3. Combined experimental (FT-Raman) and theoretical (Raman) spectra of EPHDPM

Fig. 4. Variations of entropy and enthalpy with temperature of compound EPHDPM

-9.758e-2
9.758e-2
Fig. 5. Molecular electrostatic potential for EPHDPM

(ES) ELUMO = -1.14eV
∆E = 4.27eV
(GS) EHOMO = -5.42eV
Fig. 6. HOMO-LUMO Energy diagram of EPHDPM