Quantum chemical approach towards the secondary amino derivatives of C(3) substituted 1,4-naphthoquinone: Combined molecular and dft calculations

Article abstract of DOI:10.1016/j.molstruc.2019.127306

Here we present molecular geometry of 2-chloro-3-(N,N-dimethyl amino)-1,4-naphthoquinone; DCDA, 2-chloro-3-(N,N-diethyl amino)-1,4-naphthoquinone; DCDA-2, 2-chloro-3-(N,N-dipropyl amino)-1,4-naphthoquinone; DCDA-3; 2-bromo-3-(N,N-dimethyl amino)-1,4-naphthoquinone; DBDA, 2-bromo-3-(N,N-diethyl amino)-1,4-naphthoquinone; DBDA-2, and 2-bromo-3-(N,N-dipropyl amino)-1,4-naphthoquinone; DBDA-3 obtained by employing density functional theory using basic functional CAM-B3LYP. Single crystal X-ray structure was solved for DCDA-2 which crystallizes in P2₁/n space group. Molecular frameworks are significant with hydrogen bonding interactions and were observed via. O (2)???H (13)???C (13), two benzenoid moiety possess π-π stacking interactions. Effect on the electro-optic behavior by halogen and aliphatic chain has been addressed by similar level of theory. Furthermore it was presumed that asymmetric polarizability induced by these investigated compounds displays enhanced non linear response and could be considered potential candidates for electro-optic and nonlinear optical applications.

Full text of DOI:10.1016/j.molstruc.2019.127306

Journal Pre-proof
Quantum chemical approach towards the secondary amino derivatives of C(3)
substituted 1,4-naphthoquinone: Combined molecular and dft calculations
Umar Ali Dar, Nasarul Islam, Shakeel A. Shah, Sunita Salunke-Gawali, Syed M.A.
Andrabi, Yugal Khujaria
PII:
S0022-2860(19)31415-2
DOI:
https://doi.org/10.1016/j.molstruc.2019.127306
MOLSTR 127306
Reference:
To appear in: Journal of Molecular Structure
Received Date: 20 December 2018
Revised Date: 3 September 2019
Accepted Date: 27 October 2019
Please cite this article as: U.A. Dar, N. Islam, S.A. Shah, S. Salunke-Gawali, S.M.A. Andrabi, Y.
Khujaria, Quantum chemical approach towards the secondary amino derivatives of C(3) substituted 1,4-
naphthoquinone: Combined molecular and dft calculations, Journal of Molecular Structure (2019), doi:
https://doi.org/10.1016/j.molstruc.2019.127306.
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Quantum chemical approach towards the secondary amino derivatives of C(3) substituted
1,4-naphthoquinone: Combined molecular and dft calculations
*
, 1, 4
2
*, 1
*, 4
Umar Ali Dar
,
Nasarul Islam , Shakeel A. Shah , Sunita Salunke-Gawali , Syed M. A.
4
5
Andrabi Yugal Khujaria .
,
1
Department of Chemistry, National Institute of Technology Srinagar, Hazratbal, Srinagar-
1
90006, J&K India.
2
Department of Chemistry, Govt Degree College Sopore-193201, J& K India.
University Science Instrumentation Centre, University of Kashmir, Srinagar-190006, J&K
3
India.
4
Department of Chemistry, Savitribai Phule Pune University, Pune-411007, India.
5
School of Physics, Shri Mata Vaishno Devi University, Kakryal, Katra-182320, India.
Abstract
Here we present molecular geometry of 2-chloro-3-(N,N-dimethyl amino)-1,4-naphthoquinone;
DCDA, 2-chloro-3-(N,N-diethyl amino)-1,4-naphthoquinone; DCDA-2, 2-chloro-3-(N,N-
dipropyl amino)-1,4-naphthoquinone; DCDA-3; 2-bromo-3-(N,N-dimethyl amino)-1,4-
naphthoquinone; DBDA, 2-bromo-3-(N,N-diethyl amino)-1,4-naphthoquinone; DBDA-2, and 2-
bromo-3-(N,N-dipropyl amino)-1,4-naphthoquinone; DBDA-3 obtained by employing density
functional theory using basic functional CAM-B3LYP. Single crystal X-ray structure was solved
for DCDA-2 which crystallizes in P2 /n space group. Molecular frameworks are significant with
1
hydrogen bonding interactions and were observed via. O(2)ꢀꢀꢀH(13)ꢀꢀꢀC(13), two benzenoid
moiety possess π-π stacking interactions. Effect on the electro-optic behavior by halogen and
aliphatic chain has been addressed by similar level of theory. Furthermore it was presumed that
asymmetric polarizability induced by these investigated compounds displays enhanced non linear
response and could be considered potential candidates for electro-optic and nonlinear optical
applications.
Key words: Secondary amine derivatives, 1, 4-naphthoquinone, NLO, DFT studies
*
Corresponding author
Contact No: +91-7889522122

E-mail: umar74202@gmail.com; (Umar Ali Dar),
drshakeelshah@gmail.com; (Shakeel A. Shah),
sunitas@unipune.ac.in; (Sunita A. Salunke).
1
.
Introduction
Naphthoquinones are a class of molecules that are naturally occurring chromatic pigments in
plants, fungi and some animals, and exhibit potentially useful medicinal properties [1]. The
clinical importance of 1,4-naphthoquinone has stimulated enormous interest in this class of
compounds [2,3]. Many amino and heterocyclic derivatives of 1,4-naphthoquinones have
extremely rich biological activities because of their redox potentials [4,5]. These derivatives have
been found to possess marked antiviral [6], molluscidal [7], antimalarial [8], antileishmanial [9],
antiproliferative [10], antibacterial and antifungal activities [10,11]. Biological activity of
quinones has been related to their capacity to accept one or two electrons to form the
corresponding radical anion or radical dianion [12]. The electron uptake capacity of a given
quinone can be modified by directly adding substituent’s to the quinone structure. The chemistry
of quinone dependents on the substituent’s being either on the quinonic or on adjacent rings. This
reflected in their chemical reactivity, especially in heterocyclic quinones [13,14]. Structural
aspects are very important factor as for as the biological activity of the synthetic molecules are
concerned. The interesting biological response resulting from presence of hetero atom, sulphur or
nitrogen in 1,4-naphthoquinnone prompted us to synthesis nitrogen containing halogen
derivative of 1,4-napthoquinone [15,16]. David et. al. also reported the similar compounds from
2
-methoxy derivatives with secondary amines derived from lapachole, nor-lapachole and
lawsone [17]. Author further reported no product were obtained for the 2-methoxylapachol with
secondary amines. Reactivity of substituted naphthoquinone with secondary amines can be
tailored by the presence of side chain substituents in natural and synthetic quinone. Efforts are
still on to understand the structural and functional models of new naphthoquinone compounds
containing hetro atoms like (O, N, S). Similarly in recent years computational methods were
extended to experimental methods to provide deeper understanding with regards to structural
relationship and influence of donor, acceptor functional groups on NLO properties alongside
with that of solvent effect [12,16]. To this view we aim to synthesize the C(3) substituted

secondary amine derivatives of chlorolawsone; (Clw) and bromolawsone; (BrLw). Investigated
compounds were subjected to various experimental and analytical studied further corroborated
with DFT calculations. Electro-optic and nonlinear response has been discussed briefly in
coming sections.
2
.
Experimental
2
.1 Materials and Methods
All the chemicals used in synthesis of 2-halo-3-(N, N-dialkyl amino)-1,4-naphthoquinone
are of analytical grade. 2, 3-dichloro-1,4-naphthoquinone and 2,3-dibromo-1,4-naphthoquinone
have been obtained from Sigma-Aldrich, di-ethyl amine, di-propyl amine and dichloromethane
were obtained from Merck.
2
.2 Analytical Methods
FT-IR spectra of DCDA and DBDA series have been recorded between 400 cm to 4000
-1
-1
cm using KBr pellets on Bruker Tensor 37 (Fig.S2/ S2a in ESI†). The elemental analysis has
1
been performed on Elementar Vario EL II. HNMR was recorded in CDCl
3
(Fig.S3 ESI†) with
TMS; (tetramethylsilane) used as reference. A UV-Visible spectrum was recorded on
SHIMADZU UV 1800 in methanol ranging from 200 to 800 nm (Fig.S1/ S1a. in ESI†). Melting
point of DCDA-2/3 and DBDA-3 was determined using melting point apparatus (Make-
MATTLER).
2
.3 Synthesis
Synthesis of 2-halo-3-(N,N-dialkyl amino)-1,4-naphthoquinone; DCDA-2/3 and DBDA-3
,3-dihalo-1,4-naphthoquinone; halo = chloro/ bromo (1g; 3.95 mmol) was dissolved in
0 ml of dichloromethane and stirred for 15 min. To this solution, drop wise addition of dialkyl
amine i.e. (diethyl and dipropyl amine) was done with constant stirring at room temperature
35°C) for about 24 h [19]. The progress of the reaction and the purity of the ligand were
2
2
(
monitored by thin layer chromatography. Red colored solid were obtained on evaporation of the
solvent. The crude product was purified by column chromatography using toluene as mobile
phase. The crystals for X-ray analysis were obtained by recrystallization from methanol.

2
.4 Characterization of DCDA-2
Red solid, Yield: 0.971 g (84%), m.p. 208 ºC. Anal. data calc. for C H ClNO : C, 63.76;
1
4
14
2
_
1
H,5.35; N,5.31 Found: C, 63.33, H, 5.706; N, 5.57 FT-IR (KBr, νmax/cm ): 3327, 3267, 3183,
3
1
071, 2969, 2926, 2864, 2683, 1958, 1674, 1640, 1584, 1545, 1447, 1402, 1364, 1323, 1286,
1
258, 1223, 1134, 1084, 1016, 980, 939, 849, 804, 787, 717, 681, 648, 552, 465. HNMR
(
CDCl , 300 MHz, δ/ppm: 7.91 (1H, d, J = 7.50), 7.88 (1H, d, J = 7.2, 2H, Ar),7.74 (1H, t, J =
3
1
3
7
3
4
.75),7.71 (1H, t, J = 8.00), 3.4 (4H, q, J =6.9 Hz), 1.09, (6H, t, J =7.05) . CNMR (CDCl ,
3
00MHz, δ/ppm): 182, 177, 150, 133, 132, 131, 126, 125, 46, 13. UV–Vis (λmax/nm, methanol):
93, 289.
2
.5 Characterization of DCDA-3
Red solid, Yield: 0.925 g (83%), m.p. 204 ºC. Anal. data calc. for C H ClNO : C, 65.86; H,
1
6
18
2
_
1
6
2
1
.22; N, 4.80 Found: C, 65.32, H, 5.70; N, 4.57 FT-IR (KBr, νmax/cm ): 3329, 3267, 3187, 3079,
965, 2927, 2865, 2684, 1957, 1674, 1640, 1583, 1545, 1445, 1401, 1365, 1322, 1286, 1258,
1
222, 1135, 1085, 1015, 980, 939, 849, 804, 787, 718, 681, 648, 552, 465. HNMR (CDCl
3
, 300
MHz, δ/ppm: 7.91 (1H, m, J = 7.50), 7.88 (1H, m, J = 7.2, 2H, Ar),7.74 (1H, m, J = 7.75), 7.71
1m, t, J = 8.00), 3.5 (4H, t, J = 6.9 Hz), 1.90, (4H, m, J = 7.05), 0.90,(6H, t, J =7.1 Hz) .
UV–Vis (λmax/nm, methanol): 496, 290.
(
2
.6 Characterization of DBDA-3
Red solid, Yield: 0.915 g (87%), m.p. 206 ºC. Anal. data calc. for C H BrNO : C, 57.16; H,
1
6
18
2
_
1
5
2
1
.40; N, 4.17 Found: C, 58.32, H, 5.70; N, 4.21 FT-IR (KBr, νmax/cm ): 3347, 3268, 3182, 3071,
969, 2925, 2863, 2683, 1958, 1674, 1640, 1585, 1546, 1447, 1402, 1364, 1323, 1286, 1258,
1
224, 1134, 1084, 1016, 980, 940, 849, 804, 787, 717, 681, 649, 554, 465. HNMR (CDCl , 300
3
MHz, δ/ppm: 8.1 (1H, m, J = 7.50), 7.98 (1H, d, J = 7.2, 2H, Ar),7.84 (1H, d, J = 7.75),7.74
1H, t, J = 8.00), 3.5 (4H, t, J = 6.9 Hz), 1.56, (4H, m, J = 7.05), 1.14,(6H, t, J =7.1 Hz)
(λmax/nm, methanol): 490, 288.
(
.

2
.7 X-Ray Crystallographic Data Collection and Refinement of the Structure
Crystals of DCDA-2 i.e. 2-chloro-3-(N,N-diethyl amino)-1,4-naphthoquinone suitable for
diffraction studies were chosen carefully under microscope. The unit cell parameters and the
intensity data were collected on a Bruker APEX-II CCD diffractometer, both equipped with a
fine-focus Mo-Kα (λ= 0.71073Å) X-ray source. The data for DCDA-2 was collected with the
combination of phi and omega scans with a scan width of 0.5° [sample to detector distance = 40
mm] and the SAINT software was used for data reduction. Absorption corrections were made
using SADABS program [20]. The structure was solved and refined using the SHELXL-97 [21]
programs. The crystal data was collected at room temperature and solved by direct methods. All
the non-hydrogen atoms were refined anisotropically. Hydrogen atoms were located by
difference fourier analysis and refined isotropically.
(a)
(b)
Fig. 1: (a) ORTEP plot of DCDA-2. The ellipsoids were drawn with 50 % probability (b)
Optimized structure for DCDA-2.

Table 1: Crystal data and Structure refinement for DCDA-2
Sample Code
DCDA-2
Empirical formula
Formula weight
Temperature
14 2
C H14ClN O
263.71
293(2) K
0.71073 Å
Wavelength
Crystal system, space group Monoclinic, P2 /n
1
Unit cell dimensions
a = 5.080(5) Å, α = 90°(5)
b = 17.681(5) Å, β = 96.7°(5)
c = 14.093(5) Å, γ = 90°(5)
3
Volume
Z, Calculated density
F(000)
1257.12(14) Å
-3
4, 1.393 Mg/m
552.0
Crystal size
Theta range for data
collection
0.16 x 0.11 x 0.09 mm
5.45 to 56.556
Limiting indices
-6 ≤ h ≤ 6, -23 ≤ k ≤ 23,
-16 ≤ l ≤ 18
Reflections collected /
unique
3108 / 7697 [R(int) = 0.0278]
Completeness of theta
Absorption correction
25.24
Empirical
99.8%
Max. and min. transmission 0.81 and 0.73
2
Refinement method
Full-matrix least-squares on F
Data/ restraints / parameters 3108 / 0 / 163
2
Goodness-of-fit on F
Final R indices [I>2σ(I)]
R indices (all data)
1.040
R1 = 0.0392, wR2 = 0.1108
R1 = 0.0476, wR2 = 0.1178
Absolute structure parameter Na
Largest diff. peak and hole 0.29 and -0.15 e. Å
-3
3
. Computational Method:
Density functional calculations of DCDA and DBDA series were carried out by using the
Gaussian 09 quantum chemical program [22]. Geometries of DCDA and DBDA series were fully
optimized by using CAM-B3LYP functional in conjugation with 6-311 G ++ (d, p) basis set
[23]. The ground state structure has been determined by standard force-minization processes and
the vibrational spectrum has been systematically determined to check that all vibrational
frequencies are real. On the basis of the optimized ground state structure, UV-Visible absorption
spectra in solvents (acetone, water and toluene) were carried out by using the time-dependent

density functional theory; (TD-DFT) in association with polarized continuum solvent model
PCM) [24]. The optimized molecular geometry of DCDA and DBDA series have been
(
calculated using DFT/ CAM-B3LYP method with 6-311G++ (d, p) basis set and the geometry of
molecules are shown in (Fig. 2).
DCDA
DCDA-2
DCDA-3
DBDA
DBDA-2
DBDA-3
Fig. 2: Geometries of DCDA and DBDA series optimized at CAM-B3LYP/6-311G ++ (d, p)
level of theory.

HOMO-1
HOMO
LUMO
LUMO+1
DCDA
DCDA-2
DCDA-3
DBDA
DBDA-2
DBDA-3
Fig. 3: Frontier molecular orbitals of DCDA and DBDA series calculated at CAM-B3LYP level
of theory

4
. Result and Discussion
Treatment of 2,3-dichloro-1,4-naphthoquinone and 2,3-dibromo-1,4-napthoquinone with N,N-
dialkyl amine i.e. diethyl and dipropyl in dichloromethane where carried out at room temp
(
35°C) without use of any catalyst led in the formation of 2-chloro-3-(N-N-dialkylamino)-1,4-
naphthoquinone and 2-bromo-3-(N-N-dialkylamino)-1,4-napthoquinone with yield more than 80
in polar protic solvent [25]. The reaction scheme (Scheme 2) follows michael addition
%
reaction. The nucleophile attacks on C(3) position that is most likely reaction site resulting, the
formation of compound 5. Mechanically, it is predicted that michael addition of secondary amine
2
will generate intermediate (3a/ 3b). It is believed to reorganize key intermediate (4a/ 4b),
which depicts idea about elimination of hydrogen halide i.e. (hydrogen bromide or hydrogen
chloride) by two possible pathways (A & B) as shown in (scheme 2). Path-A represents the enol
form of 4 that is directly converted into compound 5a by keto-enol tatomerization with the loss
of the “X= Cl, Br” These derivatives where purified by using thin layer chromatography and
were dried on vacuum rotary evaporators. FT-IR spectrum both (experimental and theoretical)
are presented in [Fig.S2/ S2a in ESI†] and various characteristic frequencies for important
-1
functional group are presented in Table 2. The band observed at ~1674 cm is assigned to ν
C=O
-1
stretching frequency for DCDA-2 & DBDA-3, it is observed at 1680 cm for DCDA-3. νC-H
-1
-1
(aliphatic) and νC-H (aromatic) appears at ~3267 cm
and ~2959 cm with increases in
-1
frequency by (±2) cm for other derivatives. The characteristic ν
frequency is observed at
C-N
-1
-1
~
1585 (±2) cm . The p-naphthoquinone and ν
was respectively assigned ~1257 (±2) cm and
C-Br
-1
~
717 cm for DCDA-2/3 and DBDA-3. However theoretical FT-IR frequencies show variation
-1
1
of about ±75 cm for all characteristic functional groups in reported compounds. HNMR of
compounds were recorded in CDCl aromatic protons appears at, C5(H) and C8(H) showed
3
doublet at δ = 7.88 (±0.25) whereas, protons C(6) H and C7 (H) showed triplets at δ = 7.74
(±0.25), the peaks due to aliphatic hydrogen’s are observed between δ= 1-3.5 ppm. A quartet is
observed for protons for C(11) and C(11') whereas C(12) and C(12') shows triplet for DCDA-2
and similar pattern of splitting extent for other alkyl substitute derivatives with slight down field
shift by (±0.5) (Fig.S3 in ESI†). UV-visible spectrum was recorded between 200 and 800 nm in
methanol, exhibiting four bands. Two bands in UV region at ~284, ~289 For DCDA to DBDA
series were assigned as π-π* transitions of quinonoid and benzenoid rings with no effect on
electron spectra on increase of alkyl chain however it and show slight red shift by (±5) against

the bromo derivatives, a single broad band in visible region at ~493 (±5) nm for all the
corresponding compound has been described as n-π* charge transfer (CT) transition (Fig.S1/ S1a
in ESI†), which are in good agreement with theoretical values.
-1
Table 2: Characteristic FT-IR frequencies in cm of DCDA and DBDA series.
DCDA
Theoretical Exp.
DCDA-2
Theoretical Exp.
DCDA-3
DBDA
DBDA-2
DBDA-3
Theoretical
Theoretical Theoretical Theoretical Exp.
νC-H
ν=C-H
νC=O
νC-N
3248
3010
1728
1515
1255
725
3267
2959
1674
1584
1257
717
3270
3050
1740
1540
1258
730
3267
2965
1680
1583
1260
717
3380
3060
1780
1590
1270
740
2960
2952
1674
1380
1012
670
3110
2986
1686
1416
1026
676
3270 3200
2968 3100
1674 1690
1585 1450
1257 1056
ν
P-NQ
νC-X
716
690
4
.1. Single crystal X-ray diffraction studies
Fig. 1) represents the ORTEP diagram for DCDA-2. Crystal and structure refinement data is
provided in (Table 1). A molecule of DCDA-2 crystallizes in monoclinic space group in P2 /n
(
1
space group with single independent molecule in asymmetric unit cell, however unit cell possess
four independent molecules (Fig. 4). The carbonyl C(7)―O(1) and C(8)―O(2) bond distances are
~
1.21 Å and 1.22 Å that is consistent with DFT calculation showing variation of about (±0.05) at ~
.25 Å and ~1.25 Å. However the bond distances for C(9)―N(1) and C(10)―Cl(1) are 1.36/
1.38) Å and 1.73/ (1.82) Å. Distance are similar to various derivatives of amino naphthoquinones.
However the bond angle C(9)―N(1)―C(13) are ~122.21°/ (121.28°) and C(9)―N(1)―Cl(1) are
1
(

at ~ 123.12°/ (123.32°) .The molecular packing shows linear chain zig-zag. assembly (Fig. 5a) and
is oriented in such a way that they looks butterfly-like structure when viewed down a' axis (Fig.
5
b). The crystal packing depicts the molecular assembly in finite linear chain by means of
O―HꢀꢀꢀO hydrogen bond between the alternating independent molecules via. Intermolecular
hydrogen bonding although intra-molecular hydrogen bonding was also observed.
(a)
(b)
Fig.4 (a) 2 –dimensional representation of unit cell (b) unit cell in 3-D representation.
(a)
(b)
Fig.5 (a) Molecular packing down a-axis (b) Molecular packing down a'-axis forming butterfly
like pattern.
4
.1.1 Hydrogen bonding and molecular association with neighoburing association
The X-ray crystal structure facilitates polymeric network through zig-zag fashion via.
Intermolecular O(3)―H(3)ꢀꢀꢀO(4) and O(2)―H(13)ꢀꢀꢀC(8) hydrogen bonding, intra molecular
hydrogen bonding via. O(2)―H(13)ꢀꢀꢀC(13). The independent molecules in unit cell have two

neighboring molecules via. intramolecular hydrogen bonding and π-π stacking interaction
between quinonoid and benzenoid rings [26]. The polymorphic chain forming via. O(2)―C(8)
and O(2)―C(13) in a zig-zag regular pattern showing carpet like appearance (Fig. 6)
(a)
(b)
Fig. 6 (a) Intramolecular hydrogen bonding (b) Polymeric chain forming in zig-zag fashion.
Table 3: Analysis of potential hydrogen bonds of DCDA-2
_
_
DCDA-2
Sr. no
D HꢀꢀꢀA
DꢀꢀꢀH (Å)
HꢀꢀꢀA (Å)
DꢀꢀꢀA (Å)
D HꢀꢀꢀA (º)
(
intra)
1
.
O(1)-H(6)ꢀꢀꢀC(6)
0.820(3)
2.487
2.297
2.521
2.435
2.453
2.452
2.290 (3)
0.960
2.321
0.931
0.969
1.222
0.970
2.674(4)
3.040
2.742
2.801
3.079
3.520
2.452
109.2(2)
116.60
107.02
97.16
O(1)-H(12B)ꢀꢀꢀC(12)
O(1)-H(11A)ꢀꢀꢀC(11)
O(2)-H(3)ꢀꢀꢀC(3)
Cl(1) )-H(13B)ꢀꢀꢀC(13)
123.58
144.51
149.58
(inter)
2
.
O(2)-H(13)ꢀꢀꢀC(8)
O(2)-H(13)ꢀꢀꢀC(13)
Symmetry operators (i) x, y, z (ii) ½ -x, ½ +y, ½ -z (iii) –x, -y, -z (iv) ½ -x, ½ +y, ½ -z
4
.2 Computational Calculations
The calculated structural parameters of the DCDA-2 molecule are listed in (Table 1-4 in ESI†)
and these parameters were found to be in close agreement with crystal data [22]. The slight
deviations observed may be attributed to the fact that theoretical calculations are done for single

isolated molecule in gaseous phase and the experimental values are those from of the crystalline
solid phase. This indicated that the adopted density functional and basis set are feasible for the
studied systems. The effect of change in halogen atom and extension in aliphatic chain on the
electronic properties of DCDA and DBDA series is viewed in terms of change in quantum
mechanical descriptors like ionization potential, electron affinity, chemical hardness, chemical
potential and electrophilicity index. These descriptors were calculated by employing Koopmans`
theorem i.e. ionization energy and electron affinity are the eigen value of the HOMO and LUMO
with change of sign [27]. The DCDA series displays higher values of IP, EA and electrophilicity
index than DBDA series possibly due to presence of more electronegative halogen group in
former than the later. From the (Table 4) by combining the relationships between IP values and
presence of low lying HOMO and LUMO energy level signifies that the studied systems possess
high oxidation and reduction stabilities.
The components and energies of the frontier molecular orbitals are very important to
investigate the trend in charge transfer and nonlinear optical properties. A concise description of
the frontier and sub-frontier orbital’s of the DCDA and DBDA in neutral state are a shown in
(
Fig. 3). From Fig. 3, we can see the highest occupied molecular orbital’s of DCDA and DBDA
in neutral are mainly concentrated over terminal diamine substituent including halogen atom and
with a minor contribution from aromatic ring and lowest unoccupied orbital (LUMO) distributed
over entire skeleton of DCDA and DBDA moiety with increased electron density over the
heteroatoms. However in both DCDA and DBDA the HOMO-1 and LUMO+1 have maximum
contributions from the aromatic framework excluding the heteroatoms. Thus, the first excitation
will originates both from HOMO-1 and HOMO orbitals including ꢀ → ꢁ∗ and ꢁ → ꢁ∗
transitions. In order to understand the electronic absorption behaviour, we employed TD-DFT/
CAM-B3LYP level of theory for simulation of electronic states in gas phase as well as in solvent
using PCM model. The calculated excitation energies, oscillator strength and orbital contribution
for DCDA and DBDA series are given (Table 6). The calculated values display a very strong
maximum absorption peak between 442-435 nm for DCDA and DBDA derivatives in vacuo. It is
also note worthy that the maximum absorption peaks of these derivatives show the bathochromic
shift on employing polar solvent and display hypsochromic shift with less polar solvent.
Comparing the absorption spectra of DCDA and DBDA, the former displays slight bathochromic
system. However extensions in the carbon chain have not much effect onꢂꢃꢄꢅ . In this study we

calculated electronic dipole moment, molecular polarizability, and first hyper polarizability of
DCDA and DBDA series (Table 5). Polarizability and hyperpolarizability characterizes the
response of a system in an applied field. It is well known for various studies that the molecular
polarizability, hyperpolarizability and dipole moments are important for active nonlinear
2
performance of the chemical system [18]. DCDA and DBDA contained sp -hybridised carbon,
2
the electron in the p
z
-orbital of each sp -hybridised carbon atom will form π-bonds with the
neighboring p -electrons. These π-electrons are of a delocalized nature, resulting in high
z
electronic polarizability. This has also been reflected from the obtained higher polarizability
value of DCDA as compared to DBDA resulted from more effective π-conjugation. The
polarizability and hyperpolarizability were quantified by employing finite field (FF) method. In
finite filed (FF) method, when a molecule is subjected to a static field (F), the energy (E) of the
molecule is expressed as:
1
1
ꢈ
ꢆ =ꢇꢆ − ꢉ ꢋ − ꢌ ꢋ ꢋ ꢋ − ꢏꢊꢍꢎꢐꢋ ꢋ ꢋ ꢋ − ⋯ … … … .ꢇꢇꢇꢇꢇꢇꢇꢇ5
ꢊ
ꢊ
ꢊꢍ ꢊ ꢍ
ꢎ
ꢊ ꢍ ꢎ ꢐ
2
24
ꢈ
Where ꢆ is the energy of the molecule in the absence of electronic field, ꢉ is a component of
the dipole moment vector given as:
ꢖ
ꢗ
ꢒ
ꢒ
ꢒ
ꢒ
ꢉ =ꢇꢑꢉ + ꢉ +ꢇꢉ ꢕ … … … … … … … … .6
ꢅ
ꢓ
ꢔ
ꢘis the linear polarizability tensor, ꢙ and ꢚ are the first and second hyperpolarizability tensors
and i, j and k are labels for x y and z components respectively and are given as
1
〈
ꢌ〉 =ꢇ ꢗ ꢑꢌ +ꢇꢌꢓꢓ + ꢌ ꢕ … … … … … … … 7
ꢅꢅ
ꢔꢔ
3
ꢛ =
ꢖ
ꢗ
ꢒ
ꢒ
ꢒ
ꢒ
ꢇꢜꢑꢛꢅꢅꢅ +ꢇꢛꢅꢓꢓ ꢇ+ꢇꢛꢅꢔꢔꢕ +ꢇꢑꢛ
+ꢇꢛꢓꢔꢔ ꢇ+ꢇꢛꢓꢅꢅꢕ +ꢇꢑꢛ +ꢇꢛꢔꢅꢓ ꢇ+ꢇꢛꢔꢓꢓꢕ ꢝ ꢞꢟꢛ =
ꢓꢓꢓ
ꢔꢔꢔ
ꢖ
ꢒ
ꢒ
ꢒ
ꢗ
[
ꢛ + ꢛ +ꢇꢛ ]ꢇ
ꢒ
………….8
ꢅ
ꢓ
ꢔ
ꢒ
ꢒ
ꢒ
Whereꢛ , ꢛ and ꢛ are the components of the second order polarizability tensors and can be
ꢅ
ꢓ
ꢔ
calculated by using equations:
1
ꢛ = ꢛ +ꢇ ꢠꢡꢑꢛ +ꢇꢛꢍꢊꢍ +ꢇꢛ ꢕꢢ, ꢣꢇ, ꢤ, = ꢥ, ꢦ, ꢧ … … 9
ꢊ
ꢊꢊꢊ
ꢊꢍꢍ
ꢍꢍꢊ
3
ꢊꢨꢍ
The calculated polarizability and first order hyperpolarizability of DCDA and DBDA have
significant higher values to define their role in NLO device (Table 4). Comparison between the
studied systems the DCDA-3 and DCDB-3 shows that highest value of β on account of increased

nonlinearity due to aliphatic chain. In addition to it the effective π-conjugation systems will
cause ring current in these system, thus will displays NLO activity even in absence of external
field. Thus, the studied system will be prone to be effective material for the nonlinear devices.
Table 4: Frontier molecular orbital energies, ionisation potential; (IP) and electron affinity;
(EA), quantum mechanical descriptors calculated at CAM-B3LYP/6-311G ++ (d, p)
level of theory
Derivatives ꢰꢸꢹꢺꢹ(eV)
ꢰꢻꢼꢺꢹ(eV)
-1.9171
-1.9470
-1.9383
-1.9181
-1.9489
-1.9113
ꢽꢰꢻꢾꢸ IP
EA
ꢿ
ꣀ
S
ꣁ
DCDA
-7.5235
-7.6147
-7.5796
-7.4960
-7.5834
-7.4941
5.6064 7.5235 1.9170 4.7203
2.8032 0.1783 3.9742
DCDA2
DCDA3
DBDA
5.6677 7.6147 1.9470 4.78087 2.8338 0.1764 4.0328
5.6413 7.5796 1.9383 4.75897 2.8206 0.1772 4.0146
5.5779 7.4961 1.9181 4.70713 2.7889 0.1792 3.9722
5.6345 7.5834 1.9489 4.76618 2.8172 0.1774 4.0316
5.5828 7.4942 1.9113 4.70277 2.7914 0.1791 3.9614
DBDA2
DBDA3
Table 5: Calculated values of dipole moment, polarizability and hyperpolarizability for DCDA
and DBDA chemical systems.
-
24
-32
Derivatives
DCDA
ꢁ(debye)
3.0011
2.5556
2.7296
2.8604
2.4026
2.7472
α (x 10 esu.)
23.2020
β (x 10 esu.)
7542.9611
DCDA-2
DCDA-3
DBDA
26.7743
7487.1713
8983.3507
6884.9941
6806.9276
6958.4331
30.3515
22.6822
DBDA-2
DBDA-3
27.6592
31.0748
*
∗ ′ꢩ′ electronegativity;ꢇ′ꢪ′ hardness ; ‘S’ Softness; ′ꢫ′ electrophilicity index.
Table 6: Wavelength (ꢬꢭꢮꢯ (nm)), excited state energies(∆ꢰ ꢇ(ꢲꢳ)), oscillator strengths (ꢴꢵꢶꢷ)
ꢱꢲ
and molecular orbital contributions of DCDA and DBDA series calculated using TD-
DFT method at CAM-B3LYP/6-311G ++ (d, p) level in acetone, water and toluene.

Derivative
ꢬꢭꢮꢯ
∆ꢰꢱꢲ
ꣂꢞꣃ꣄
Orbital Contribution (%)
DCDA (acetone)
439.90 2.8184
440.00 2.8178
437.53 2.8337
433.23 2.8618
433.34 2.8611
430.91 2.8772
435.41 2.8475
433.34 2.8469
433.26 2.8616
442.95 2.7990
443.01 2.7986
440.86 2.8123
437.62 2.8331
437.73 2.8324
435.44 2.8473
440.12 2.8170
440.18 2.8166
438.54 2.8272
0.0915
0.0915
0.0944
0.0960
0.0951
0.0989
0.0992
0.0983
0.1018
0.0873
0.0868
0.0911
0.0929
0.0920
0.0964
0.0924
0.0914
0.0957
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ93%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ4%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ93%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ93%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ93%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ93%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%ꣅ − 4ꢇ → ꣈꣉꣇꣆ꢇ3%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%
(
(
water)
Toluene)
DCDA-2 (acetone)
(
(
water)
Toluene)
DCDA-3 (acetone)
(
(
water)
Toluene)
DBDA (acetone)
(
(
water)
Toluene)
DBDA-2 (acetone)
(
(
water)
Toluene)
DBDA-3 (acetone)
(
(
water)
Toluene)
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%
ꣅ꣆꣇꣆ → ꣈꣉꣇꣆ꢇ92%
5
. Conclusion
In summary a series of secondary amine halo (Cl, Br) derivatives of 1,4-naphthoquinone were
synthesized and characterized by various analytical techniques. Single crystal X-ray was solved
for DCDA-2 which crystallizes in P2 /n space group. Calculated bond angle, bond distances,
1
torsion angle and molecular geometry were in good agreement with theoretical data. Furthermore
the reported compounds have been investigated for their non linear optical properties using
density functional theory. Values obtained reflect their possible role and important candidates as
NLO material, which can be attributed to structural modification and predominate charge
transfer with the halogen substitution.
6
. Acknowledgement
U.A.D is grateful to NIT Srinagar for financial support in the form of research fellowship. U.A.D
also express sincere gratitude to Prof. Sunita Salunke-Gawali with whome he started working,
for her constant support and encouragment. Further more acknowdelegement to CIF( central
Instrumentation Facility) SPPU, Department of chemistry; Savitribai Phule Pune University for
providing research fellowship under (UPE XII) plan during the tenture of M.Phil (Session 2013-
2
015).

7
. Supporting information available
1
13
Characterization of DCDA and DBDA series by FT-IR, H and CNMR, UV-visible spectrum,
were presented in Fig. S1 to S3 respectively. Crystallographic data represented in Table 1 to 4.
Crystallographic data have been deposited with the Cambridge Crystallographic Data Centre and
may be obtained on request quoting the deposition number CCDC 1564385 for DCDA-2, from
the CCDC, 12 Union Road, Cambridge CB21EZ, UK (Fax: +44 1223 336 033; E-mail
address:deposit@ccdc.cam.ac.uk)
8
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Highlights
•
•
•
Single X-ray crystal structure of 2-chloro-3(N, N-diethyl amino)-1, 4-naphthoquinone.
Intra and inter molecular hydrogen bonding.
DFT and FMO approach towards secondary amino derivatives of C(3) substituted 1,4-
naphthoquinone.
•
Effect of halogen and extended alkyl chain on electro-optic properties.