Experimental and theoretical studies on new 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-alkyl-10H-phenothiazine-3-carbaldehydes

Article abstract of DOI:10.1016/j.molstruc.2016.11.022

Synthesis of fused heterocyclic aldehydes with carbazole (CZ) structural motif linked at C-7 position on phenothiazines (PTZ), 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-butyl-10H-phenothiazine-3-carbaldehyde (1) and 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-hexyl-10H-phenothiazine-3-carbaldehyde (2) has been accomplished and are characterized through experimental and computational techniques. The optimized structure with their bonding aspects and vibrational frequencies of the same have been examined utilizing DFT-B3LYP technique with a basis set 6-311++G(d,p). In the optimized structures of 1 and 2, the bond lengths and bond angles are in accord with their corresponding reported analogous. The vibrational frequencies resulted from experimental as well as theoretical are in well accord with each other. Further, the results of polarizabilities, first order hyperpolarizabilities and dipole moment of 1 and 2 imply that these could be utilized for the preparation of NLO crystals which might generate second order harmonic waves.

Full text of DOI:10.1016/j.molstruc.2016.11.022

Journal of Molecular Structure xxx (2016) 1e11
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Experimental and theoretical studies on new 7-(3,6-di-tert-butyl-9H-
carbazol-9-yl)-10-alkyl-10H-phenothiazine-3-carbaldehydes
Kesavan Stalindurai, Kannan Gokula Krishnan, Erumaipatty Rajagounder Nagarajan,
Chennan Ramalingan*
Department of Chemistry, Kalasalingam University, Krishnankoil, 626 126, Tamilnadu, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of fused heterocyclic aldehydes with carbazole (CZ) structural motif linked at C-7 position on
phenothiazines (PTZ), 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-butyl-10H-phenothiazine-3-carbalde
hyde (1) and 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-hexyl-10H-phenothiazine-3-carbaldehyde (2)
has been accomplished and are characterized through experimental and computational techniques. The
optimized structure with their bonding aspects and vibrational frequencies of the same have been
examined utilizing DFT-B3LYP technique with a basis set 6-311þþG(d,p). In the optimized structures of 1
and 2, the bond lengths and bond angles are in accord with their corresponding reported analogous. The
vibrational frequencies resulted from experimental as well as theoretical are in well accord with each
other. Further, the results of polarizabilities, first order hyperpolarizabilities and dipole moment of 1 and
2 imply that these could be utilized for the preparation of NLO crystals which might generate second
order harmonic waves.
Received 28 June 2016
Received in revised form
19 October 2016
Accepted 6 November 2016
Available online xxx
Keywords:
Carbazole
Phenothiazine
GIAO
Polarizabilities
Hyperpolarizabilities
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
attention towards electro-chemical [7] and electro-optical proper-
ties [8]. They are widely used as potential intermediates in chemical
Carbazole (CZ), also branded as 9-azafluorene, and its de-
rivatives are incredibly significant nitrogen possessing hetero-
aromatic compounds, which have been used as potential building
blocks in the construction of a wide range of functional materials
[1]. Besides, the CZ structural scaffold has been found in several bio-
important chemical entities and exhibit antifungal [2], antibacterial
[3], anti-inflammatory [4], antiviral [5], and antitumor properties
[6]. Alkyl functionalized carbazoles play noteworthy roles in elec-
tron transport materials/dye-sensitized solar cells. For instance, it is
known that CZ is an electron donor because of the existence of lone
pair of electrons on the nitrogen. Since alkyl groups are electron
donors in nature through inductive effect, incorporation of such
groups on the CZ structural motif enhances the electron donating
ability of the CZ unit. Further, introduction of alkyl groups helps in
enhancing the materials solubility as well.
manufacturing and active components of organic light emitting
diodes (OLEDs) [9], semiconductors [10] and solar cells [11]. Besides
their potential applications in materials science, PTZ has been uti-
lized to construct chemical entities of biological significance which
display various activities including anti-malarial [12], anti-cancer
[13], anti-helminthic [14], anti-histamine [15] and anti-psychotic
activity [16].
The wide variety of applications of organic molecules possessing
CZ and PTZ structural motifs reported in the literature inspired us to
focus our attention towards new systems carrying these two
carbazole-phenothiazine moieties. We herein report synthesis as
well as experimental and computational studies on compounds 1
and 2. Structural parameters (optimized) were obtained by the
calculations of density functional theory (DFT) with a basis set
B3LYP/6-311þþG(d,p). From the theoretical results, vibrational
assignments and optimized structural parameters are deduced and
these outcomes are correlated with the experimental results. The
theoretical outcomes are found to be appreciably comparable with
the experimental results.
Phenothiazine (PTZ) and its derivatives are one of the classes of
outstanding heterocyclic compounds with excellent electron
donating nature and hence these trigger researchers to focus their
* Corresponding author.
E-mail address: ramalinganc@gmail.com (C. Ramalingan).
http://dx.doi.org/10.1016/j.molstruc.2016.11.022
0022-2860/© 2016 Elsevier B.V. All rights reserved.
Please cite this article in press as: K. Stalindurai, et al., Experimental and theoretical studies on new 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-
alkyl-10H-phenothiazine-3-carbaldehydes, Journal of Molecular Structure (2016), http://dx.doi.org/10.1016/j.molstruc.2016.11.022

2
K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
Scheme 1. Synthesis of 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-alkyl-10H-phenothiazine-3-carbaldehydes.
Fig. 1. Optimized structure and Mulliken charge distribution indicated by color code of compounds 1 and 2.
2. Experimental section
condenser under nitrogen atmosphere, was charged bromophe-
nothiazine carbaldehyde 8 (0.50 g, 1.38 mmol), alkylcarbazole 11
(0.39 g, 1.38 mmol), potassium carbonate (0.6 g, 4.34 mmol),
copper-bronze (0.14 g, 2.16 mmol), and 18-crown-6 (0.06 g,
0.20 mmol). Then, 1,2-Dichlorobenzene (20 mL) was added using a
syringe and stirred for two minutes. It was then heated to reflux
and continued the same with stirring for 48 h. After cooling, it was
filtered and the dark-brown filtrate-solution was collected. The
insoluble material was rinsed with dichloromethane (3 ꢁ 30 mL).
The rinsed solution thus obtained together with the collected dark-
brown filtrate was washed with a dilute solution of aqueous
ammonia followed by water. The washed dichloromethane, after
drying over anhydrous magnesium sulfate, was evaporated with
the help of rotary evaporator to provide a crude mixture. The pure
title compound was eventually obtained upon column chromato-
graphic separation using hexane-dichloromethane mixture (4:6).
Yield: 0.56 g (73%), mp. 218e220 ꢂC. IR (KBr, cmꢀ1): 3055e2713 (C-
2.1. Characterization
The melting point of the title heterocyclic carbaldehydes was
measured in capillaries (open) and is un-corrected. IR spectra of the
synthesized molecules were acquired on Shimadzu IR Tracer-100 in
the range between 400 and 4000 cmꢀ1 utilizing KBr pellet form
(resolution e 04; number of scans - 25). The spectral assignments
are reported in wavenumber (cmꢀ1). Spectra of 1H and 13C NMR
were obtained on Bruker spectrometer (400 MHz) using
chloroform-D (CDCl3) as a solvent. The values of chemical shifts are
given in parts per million (ppm) from tetramethylsilane (TMS).
UVeVis spectra of the molecules have been obtained in dichloro-
methane (DCM), hexane, and ethanol in the region 200e800 nm
and the spectrophotometer used for the same is JASCO V-650.
Haromatic
aliphatic), 1693 (C]Oaldehyde), 1602, 1579 (C]C), 1257,
&
2.2. Synthesis of heterocyclic carbaldehydes 1 and 2
1236 (CeN), 1101 (CeS); 1H NMR (400 MHz, CDCl3):
d 9.82 (s, 1H),
8.12 (d, J ¼ 1.20 Hz, 2H), 7.70e7.68 (m, 1H), 7.62 (s, 1H), 7.47e7.44
(m, 2H), 7.34e7.26 (m, 4H), 7.04 (d, J ¼ 6.00 Hz, 1H), 6.97 (d,
J ¼ 8.40 Hz, 1H), 3.97 (t, J ¼ 7.20 Hz, 2H), 1.92e1.85 (m, 2H),
1.63e1.52 (m, 2H), 1.45 (s, 18H), 1.01 (t, J ¼ 7.40 Hz, 3H); 13C NMR
2.2.1. Synthesis of intermediates
The intermediates, alkylphenothiazines 4 and 5, alkylpheno-
thiazine carbaldehydes 6 and 7, bromophenothiazine carbalde-
hydes 8 and 9, and alkylcarbazole 11 were synthesized by
employing literature methods [17e19].
(400 MHz, CDCl3):
d 190.00, 150.39, 142.94, 142.34, 139.25, 133.81,
131.31,130.24, 128.65, 125.88, 125.69,125.36, 124.50, 123.65, 123.30,
116.59,116.29,115.03,109.12, 47.99, 34.77, 32.04, 29.74, 20.18,13.84;
Anal. Cald for C37H40N2OS: C, 79.24; H, 7.19; N, 5.00; S, 5.72. Found:
2.2.2. Synthesis of heterocyclic carbaldehyde 1
In a double neck round-bottomed flask (100 mL) with water
Please cite this article in press as: K. Stalindurai, et al., Experimental and theoretical studies on new 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-
alkyl-10H-phenothiazine-3-carbaldehydes, Journal of Molecular Structure (2016), http://dx.doi.org/10.1016/j.molstruc.2016.11.022

K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
3
Table 1
Selected bond lengths and bond angles of compounds 1 and 2.
Bond length
1
2
Expt
Bond length
1
2
Expt
C1eC2
C1eC14
C2eC3
C3eC4
C3eC15
C4eC5
C5eS6
C5eC14
S6eC7
C7eC8
C7eC12
C8eC9
C9eC10
C9eN17
C10eC11
C11eC12
C12eN13
N13eC14
N13eC38
C15eO16
N17eC18
N17eC29
C18eC19
C18eC23
1.391
1.413
1.400
1.407
1.464
1.383
1.838
1.417
1.835
1.391
1.407
1.401
1.397
1.423
1.394
1.408
1.426
1.411
1.482
1.243
1.410
1.410
1.397
1.416
1.391
1.409
1.402
1.407
1.466
1.383
1.845
1.414
1.842
1.391
1.404
1.401
1.400
1.424
1.394
1.405
1.426
1.412
1.481
1.242
1.410
1.410
1.397
1.417
1.398 (18)
1.393 (18)
1.395 (18)
1.387 (18)
e
C19eC20
C20eC21
C21eC22
C21eC34
C22eC23
C23eC24
C24eC25
C24eC29
C25eC26
C26eC27
C26eC30
C27eC28
C28eC29
C30eC31
C30eC32
C30eC33
C34eC35
C34eC36
C34eC37
C38eC39
C39eC40
C40eC41
C41eC42
C42eC43
1.393
1.417
1.399
1.544
1.402
1.452
1.401
1.417
1.399
1.417
1.545
1.393
1.397
1.552
1.545
1.553
1.545
1.552
1.552
1.544
1.540
1.536
e
1.393
1.417
1.399
1.544
1.402
1.452
1.402
1.417
1.399
1.417
1.545
1.393
1.396
1.545
1.552
1.552
1.552
1.552
1.545
1.539
1.537
1.538
1.539
1.536
1.366 (4)
1.411 (4)
1.385 (4)
1.517 (4)
1.397 (3)
1.442 (4)
1.394 (3)
1.398 (3)
1.379 (3)
1.411 (4)
1.523 (4)
1.371 (4)
1.372 (4)
1.524 (4)
1.520 (4)
1.539 (4)
1.514 (4)
1.520 (4)
1.541 (4)
e
1.391 (18)
1.761 (13)
1.403 (18)
1.766 (14)
1.389 (18)
1.400 (18)
1.393 (2)
1.384 (2)
e
1.390 (2)
1.394 (18)
1.395 (17)
1.393 (16)
e
e
1.376 (4)
1.380 (4)
1.382 (4)
1.400 (3)
e
e
e
e
e
Bond angle
1
2
Expt
Bond angle
1
2
Expt
C2eC1eC14
C1eC2eC3
C2eC3eC4
C2eC3eC15
C4eC3eC15
C3eC4eC5
121.2
120.9
118.4
120.8
120.8
120.7
118.2
121.6
119.9
98.0
120.7
120.8
118.9
120.5
120.6
120.2
120.0
121.4
118.5
96.7
120.8 (12)
119.7 (12)
119.6 (12)
e
C20eC21eC22
C20eC21eC34
C22eC21eC34
C21eC22eC23
C18eC23eC22
C18eC23eC24
C22eC23eC24
C23eC24eC25
C23eC24eC29
C25eC24eC29
C24eC25eC26
C25eC26eC27
C25eC26eC30
C27eC26eC30
C26eC27eC28
C27eC28eC29
N17eC29eC24
N17eC29eC28
C24eC29eC28
C26eC30eC31
C26eC30eC32
C26eC30eC33
C31eC30eC32
C31eC30eC33
C32eC30eC33
C21eC34eC35
C21eC34eC36
C21eC34eC37
C35eC34eC36
C35eC34eC37
C36eC34eC37
N13eC38eC39
C38eC39eC40
C39eC40eC41
C40eC41eC42
C41eC42eC43
e
118.0
119.3
122.7
120.5
119.9
107.0
133.1
133.1
107.1
119.8
120.5
118.0
122.6
119.3
122.8
118.0
108.9
130.2
120.9
109.7
112.3
109.6
108.0
109.2
108.0
112.3
109.6
109.7
108.0
108.0
109.3
116.9
111.5
113.0
e
118.0
119.3
122.7
120.5
119.8
107.0
133.1
133.1
107.0
119.8
120.5
118.1
122.7
119.3
122.8
117.9
108.9
130.2
120.9
112.3
109.7
109.6
108.0
108.0
109.2
109.6
109.7
112.3
109.3
108.0
108.0
113.1
113.7
113.1
113.4
113.2
e
117.3 (3)
119.5 (3)
123.2 (3)
120.9 (2)
119.3 (3)
106.9 (2)
133.8 (2)
134.3 (2)
106.8 (2)
118.8 (3)
121.4 (2)
116.9 (3)
123.2 (2)
119.8 (3)
123.4 (3)
117.7 (3)
108.3 (3)
130.0 (3)
121.7 (3)
112.2 (2)
108.8 (2)
110.3 (2)
108.6 (3)
106.8 (2)
110.1 (3)
111.1 (3)
113.1 (3)
108.9 (3)
109.0 (3)
109.1 (3)
105.4 (3)
e
e
120.7 (12)
118.3 (10)
120.2 (12)
121.3 (10)
100.8 (6)
118.5 (10)
121.2 (10)
120.2 (12)
120.4 (13)
119.5 (13)
e
C4eC5eS6
C4eC5eC14
S6eC5eC14
C5eS6eC7
S6eC7eC8
118.1
120.1
121.6
120.6
118.6
120.5
120.9
120.5
121.6
116.9
121.9
121.1
122.6
118.3
118.7
117.1
121.2
121.8
124.8
126.0
125.9
108.0
130.2
108.9
120.9
118.0
122.8
120.1
118.4
121.5
120.1
119.1
120.3
120.6
120.4
121.0
117.9
120.6
121.5
119.6
119.1
120.1
117.9
121.8
120.2
124.7
126.0
125.9
108.1
130.2
108.9
120.9
117.9
122.8
S6eC7eC12
C8eC7eC12
C7eC8eC9
C8eC9eC10
C8eC9eN17
C10eC9eN17
C9eC10eC11
C10eC11eC12
C7eC12eC11
C7eC12eN13
C11eC12eN13
C12eN13eC14
C12eN13eC38
C14eN13eC38
C1eC14eC5
C1eC14eN13
C5eC14eN13
C3eC15eO16
C9eN17eC18
C9eN17eC29
C18eN17eC29
N17eC18eC19
N17eC18eC23
C19eC18eC23
C18eC19eC20
C19eC20eC21
e
120.4 (13)
120.5 (13)
118.9 (12)
121.5 (12)
119.6 (12)
123.4 (11)
e
e
118.8 (12)
119.7 (11)
121.5 (12)
e
e
e
e
130.6 (3)
108.2 (3)
121.1 (3)
118.1 (3)
123.3 (3)
e
e
e
e
e
e
e
C, 79.43; H, 7.22; N, 4.96; S, 5.69.
gave the title compound by adopting the above method. Yield:
0.54 g (67%), mp. 227e229 ꢂC. IR (KBr, cmꢀ1): 3055e2713 (C-Har-
omatic & aliphatic), 1693 (C]Oaldehyde), 1602, 1579 (C]C), 1255, 1197
(CeN),1143 (CeS); 1H NMR (400 MHz, CDCl3):
d 9.81 (s,1H), 8.13 (d,
2.2.3. Synthesis of heterocyclic carbaldehyde 2
A mixture of bromophenothiazine carbaldehyde 9 (0.54 g,
1.38 mmol), alkylcarbazole 11 (0.39 g, 1.38 mmol), potassium car-
bonate (0.60 g, 4.34 mmol), copper-bronze (0.14 g, 2.16 mmol), and
18-crown-6 (0.06 g, 0.20 mmol) in 1,2-dichlorobenzene (20 mL)
J ¼ 1.60 Hz, 2H), 7.68 (d, J ¼ 2.00 Hz, 1H), 7.61 (s, 1H), 7.46e7.44 (m,
2H), 7.31e7.25 (m, 4H), 7.02 (d, J ¼ 8.40 Hz, 1H), 6.94 (d, J ¼ 8.40 Hz,
1H), 3.94 (t, J ¼ 7.20 Hz, 2H), 1.91e1.87 (m, 2H), 1.61e1.59 (m, 2H),
Please cite this article in press as: K. Stalindurai, et al., Experimental and theoretical studies on new 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-
alkyl-10H-phenothiazine-3-carbaldehydes, Journal of Molecular Structure (2016), http://dx.doi.org/10.1016/j.molstruc.2016.11.022

4
K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
Fig. 2. (a) FT-IR spectrum of compound 1 (b) Simulated FT-IR spectrum of compound 1 (c) FT-IR spectrum of compound 2 (d) Simulated FT-IR spectrum of compound 2.
1.46 (s, 18H), 1.49e1.32 (m, 4H), 0.90 (t, J ¼ 4.40 Hz, 3H); 13C NMR
carbaldehydes 1 and 2 is furnished in Scheme 1. Alkylphenothia-
zine carbaldehydes 6 and 7 were synthesized from commercially
available phenothiazine 3 by alkylation using respective alkyl ha-
lides under basic condition followed by Vilsmeier-Haack reaction
using phosphorous oxychloride and N,N-dimethylformamide.
Bromination of 6 and 7 utilizing bromine as a brominating agent
provided key intermediates bromophenothiazine carbaldehydes 8
and 9, respectively. At the same time, alkyl carbazole 11 was syn-
thesized from commercially available carbazole 10 employing
alkylation reaction with alkyl halide in the presence of Lewis acid.
Copper-bronze catalyzed Ullman type coupling reaction between
the carbaldehyde intermediates 8 and 9 and the alkyl carbazole 11
eventually afforded the title heterocyclic carbaldehydes 1 and 2,
respectively in good yields (73% and 67%, respectively) and the
structures were confirmed on the basis of 1H NMR, 13C NMR, FT-IR,
and micro analysis.
(400 MHz, CDCl3):
d 190.02, 150.38, 142.94, 142.31, 139.25, 133.79,
131.29, 130.26, 128.63, 125.88, 125.67, 125.35, 124.46, 123.66, 123.31,
116.60, 116.30, 115.02, 109.13, 48.30, 34.77, 32.06, 31.45, 26.79,
26.60, 22.63, 14.05; Anal. Cald for C39H44N2OS: C, 79.55; H, 7.53; N,
4.76; S, 5.45. Found: C, 79.81; H, 7.61; N, 4.73; S, 5.43.
2.3. Computational details
The theoretical calculations of the synthesized molecules have
been performed utilizing DFT-B3LYP method with a basis set 6-
311þþG(d,p)[Gaussian 09 program package] [20]. The DFT (density
functional theory - gradient corrected) with the Becke3 (B3 - three
parameter hybrid functional) for the exchange part and the LYP
(Lee-Yang-Parr) correlation function [21], agreed as an approach of
cost-effective, have been adopted for the calculation of energies of
vibrational frequencies and optimized structures. The frequencies
computed at the aforementioned levels restrain systematic errors
which are known. To bring the theoretical frequencies in close
proximity to the experimental values, the scaling factor value [22]
of 0.96 has been used. UVeVis spectra for both gas and solution
phases were computed by time dependent-DFT with a basis set
B3LYP/6-311þþG(d,p). NMR chemical shifts were computed at
B3LYP/6-311þþG(2d,p) level utilizing the method of Gauge Inde-
pendent Atomic Orbital (GIAO) [22].
3.2. Molecular structure
The ground state optimized structure of the heterocyclic car-
baldehydes 1 and 2 has been attained by the method of B3LYP/6-
311þþG(d,p) and is furnished in Fig. 1. As shown in the figure,
the molecular structure of the parent PTZ structural motif has a
typical butterfly form. The presence of carbaldehyde and CZ moi-
eties on the 3- and 7- positions, respectively of the PTZ core in-
fluences this form to a little further extent. All the bond angles and
bond lengths in the computed ones are in-lined with similar
compounds 1-(10H-phenothiazin-2-yl)ethanone [23] and 3,6-di-
tert-butyl-9H-carbazole [CCDC No. 1480917]. The optimized CeC
bond lengths in the CZ and PTZ moieties fall in the range between
1.383 Å and 1.466 Å, which are in good accord with the bond
3. Results and discussion
3.1. Synthesis
The schematic representation for the synthesis of heterocyclic
Please cite this article in press as: K. Stalindurai, et al., Experimental and theoretical studies on new 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-
alkyl-10H-phenothiazine-3-carbaldehydes, Journal of Molecular Structure (2016), http://dx.doi.org/10.1016/j.molstruc.2016.11.022

K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
5
Table 2
The important bond angles and bond lengths are provided in
Table 1. As can be seen, some of the bond lengths and bond angles
are longer/larger and this may probably be due to the larger basis
set preferred.
Mulliken atomic charges of compounds 1 and 2.
Atom
1
2
Atom
1
2
C1
C2
C3
C4
C5
S6
C7
C8
ꢀ0.1647
ꢀ0.1290
ꢀ0.0911
ꢀ0.1245
ꢀ0.3233
0.3937
ꢀ0.3255
ꢀ0.1705
0.2760
ꢀ0.1325
ꢀ0.1388
ꢀ0.0877
ꢀ0.1282
ꢀ0.3135
0.3861
ꢀ0.3088
ꢀ0.1750
0.2760
H42/H44
H43/H45
H44/H46
H45/H47
H46/H48
H47/H49
H48/H50
H49/H51
H50/H52
H51/H53
H52/H54
H53/H55
H54/H56
H55/H57
H56/H58
H57/H59
H58/H60
H59/H61
H60/H62
H61/H63
H62/H64
H63/H65
H64/H66
H65/H67
H66/H68
H67/H69
H68/H70
H69/H71
H70/H72
H71/H73
H72/H74
H73/H75
H74/H76
H75/H77
H76/H78
H77/H79
H78/H80
H79/H81
H80/H82
H81/H83
e/H84
0.1835
0.1632
0.1915
0.1944
0.1795
0.1821
0.1259
0.1769
0.1485
0.1753
0.1756
0.1467
0.1718
0.1789
0.1695
0.1691
0.1795
0.1806
0.1704
0.1770
0.1688
0.1692
0.1801
0.1793
0.1705
0.1705
0.1783
0.1691
0.1700
0.1773
0.1692
0.2071
0.2077
0.1857
0.1874
0.1753
0.1760
0.1814
0.1771
0.1767
e
0.1790
0.1652
0.1935
0.1941
0.1809
0.1709
0.1268
0.1739
0.1481
0.1752
0.1754
0.1473
0.1719
0.1794
0.1705
0.1804
0.1789
0.1691
0.1698
0.1770
0.1692
0.1691
0.1698
0.1773
0.1691
0.1784
0.1701
0.1692
0.1804
0.1706
0.1791
0.1860
0.1987
0.1955
0.1763
0.1617
0.2097
0.1682
0.1620
0.1693
0.1754
0.1750
0.1725
0.1706
3.3. Vibrational analysis
The experimental and computed FT-IR spectra of molecules 1
and 2 are given in Fig. 2. The vibrational frequencies resulted from
experimental and computational ones [B3LYP/6-311þþG(d,p)] in
addition to their relative intensities and feasible assignments of
molecules 1 and 2 are summarized in Supplementary Tables S1 and
S2, respectively. A general observation is that the frequencies ob-
tained from computational calculations are in good concord with
the ones acquired from experimental outcomes.
The modes of stretching vibrations in the aromatic and heter-
oaromatic ring systems are receptive to various substituents and
the vibrations of the aromatic rings observed strongly in the area
1630-1480 cmꢀ1 [25]. In this investigation, the frequencies
observed in the region 1602-1471 cmꢀ1 for the compounds 1 and 2
are assigned to stretching vibrations of CeC. The results of
computational study using B3LYP/6-311þþG(d,p) method imply
that the vibrations resulted in the region 1605-1470 cmꢀ1 are
corresponds to the same. As it is known, the in-plane bending vi-
brations of CeCeC are usually occur at less than 700 cmꢀ1 and
these vibrational bands are reasonably sensitive to alteration in the
position as well as nature of the substituents [26]. In the molecules
1 and 2, the experimental CeCeC out-of-plane and in-plane
bending vibrations are observed in the area 810-504 cmꢀ1 and
the results of CeCeC out-of-plane and in-plane bending vibrations
obtained from computational analysis are also in harmony with the
experimental ones (Supplementary Tables S1 and S2).
The CeH stretching vibrations of aromatic region are usually
anticipated to emerge in the area 3100-3000 cmꢀ1 [27] and the
character of substituents do not usually influence the absorption
bands much in the region. In accordance with the aforementioned
statement, the absorption bands resulted at 3055 cmꢀ1 for both the
compounds are assigned to aromatic CeH stretching vibrations.
The obtained experimental aromatic CeH stretching vibrations
exhibit good accord with the computational results, observed at
3065 and 3056 cmꢀ1 in B3LYP method. Literature report also sup-
port for the observed frequencies of CeH stretching vibrations [28].
It has been documented that the bending vibrations of CeH out-of-
plane and in-plane modes commonly lie between 800 and
450 cmꢀ1 and 1300-1000 cmꢀ1 [27], respectively. In the current
C9
C10
C11
C12
N13
C14
C15
O16
N17
C18
C19
C20
C21
C22
C23
C24
C25
C26
C27
C28
C29
C30
C31
C32
C33
C34
C35
C36
C37
C38
C39
C40
C41
C42
C43
ꢀ0.1345
ꢀ0.1512
0.4187
ꢀ0.1392
ꢀ0.1133
0.3698
ꢀ0.8148
ꢀ0.8094
0.4396
0.4028
0.1536
0.1532
ꢀ0.3626
ꢀ1.0079
0.2709
ꢀ0.0660
ꢀ0.1533
0.0890
ꢀ0.0020
ꢀ0.1847
ꢀ0.1856
ꢀ0.0017
0.0887
ꢀ0.1529
ꢀ0.0651
0.2722
ꢀ0.2528
ꢀ0.4634
ꢀ0.5050
ꢀ0.4632
ꢀ0.2531
ꢀ0.5049
ꢀ0.4632
ꢀ0.4634
ꢀ0.2515
ꢀ0.3222
ꢀ0.3507
ꢀ0.5146
e
ꢀ0.3609
ꢀ1.0077
0.2711
ꢀ0.0660
ꢀ0.1532
0.0893
ꢀ0.0020
ꢀ0.1828
ꢀ0.1847
ꢀ0.0015
0.0890
ꢀ0.1529
ꢀ0.0654
0.2722
ꢀ0.2528
ꢀ0.5048
ꢀ0.4635
ꢀ0.4635
ꢀ0.2530
ꢀ0.4632
ꢀ0.4635
ꢀ0.5047
ꢀ0.2091
ꢀ0.3520
ꢀ0.3204
ꢀ0.3256
ꢀ0.3440
ꢀ0.5163
e/H85
e/H86
e/H87
e
e
e
e
lengths obtained from experimental results. The computed bond
lengths of CeS and CeN in PTZ ring are 1.424 Å and 1.842 Å,
respectively (deduced by B3LYP method). On comparing with
experimental values [24], these are deviated from 0.03 to 0.07 Å.
Table 3
Electronic transition of compounds 1 and 2 in gas and solution phase.
Solvent
Compound 1
Experimental
Compound 2
Calculated
(nm)
Experimental
Calculated
(nm)
l
(nm)
Abs.
l
E (eV)
f
l
(nm)
Abs.
l
E (eV)
f
Gas
421.24 (149 / 151)
369.55 (149 / 151)
349.65 (145 / 151)
428.37 (149 / 151)
369.50 (149 / 151)
341.13 (148 / 151)
427.70 (149 / 151)
368.42 (149 / 151)
339.48 (148 / 151)
427.33 (149 / 151)
371.26 (149 / 151)
345.65 (148 / 151)
2.9433
3.3550
3.5459
2.8943
3.3555
3.6345
2.8988
3.3653
3.6522
2.9014
3.3396
3.5870
0.1789
0.0299
0.0022
0.2741
0.0376
0.0002
0.2746
0.0361
0.0002
0.2478
0.0386
0.0001
409.82 (156 / 159)
360.59 (153 / 159)
348.59 (153 / 159)
415.31 (157 / 159)
363.40 (157 / 159)
340.11 (156 / 159)
414.77 (157 / 159)
362.61 (157 / 159)
338.47 (156 / 159)
414.48 (157 / 159)
363.79 (157 / 159)
344.73 (156 / 159)
3.0253
3.4383
3.5567
2.9853
3.4118
3.6454
2.9892
3.4192
3.6631
2.9913
3.4081
3.5966
0.1071
0.0696
0.0107
0.1882
0.0891
0.0003
0.1915
0.0862
0.0003
0.1593
0.0923
0.0004
DCM
EtOH
Hexane
399
351
0.1301
0.1337
0.7316
0.1263
0.1318
0.7385
0.1166
0.1136
0.6722
389.5
333
296.5
388
332
296
381
346
296.5
0.1128
0.1528
0.5308
0.1117
0.1553
0.5266
0.0528
0.1089
0.4776
294.5
403.5
353
297.5
405
350.5
296.5
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K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
experimental study, the weak to strong bands resulted at
651e572 cmꢀ1 and 1236e1197, 1143 cmꢀ1 are allocated to bending
vibrations of CeH out-of-plane and in-plane modes, respectively.
The corresponding absorptions as a result of computational studies
are noted at 1230e1192, 1163, 1149 as well as 651-596 cmꢀ1, which
are in well accord with the results of experimental ones.
carbaldehyde functionality and the counterpart resulted from
computational study are well comparable to each other.
Normally, the assignment for carbon-heteroatom stretching vi-
brations such as CeS and CeN ones is intricate in the infrared, since
the band is of inconsistent intensity and also may be noted in the
broad range between 1220 and 1080 cmꢀ1 [28,31]. The CeN and
CeS moieties are less polar than carbonyl group and have notice-
ably weaker bands. The CeN and CeS absorptions are resulted in
the FT-IR spectra of compounds 1/2 at 1257/1255 and 1029/
920 cmꢀ1, respectively and the corresponding computed values for
compounds 1/2 lie at 1262/1620 and 1024/926 as well as 1029/
915 cmꢀ1, respectively. As can be seen from the above absorptions,
the theoretically computed results are in-line with the experi-
mental ones.
In general, CeH stretching vibrations of alkyl groups/chain occur
at comparatively lower frequencies than those present in the aro-
matic rings. i.e. 2970-2840 cmꢀ1 [29]. In the FT-IR spectra of mol-
ecules 1 and 2, the CeH stretching vibrations are observed at 2956-
2713 cmꢀ1 as weak and medium bands whereas in the corre-
sponding theoretical FT-IR spectra, these vibrations of CeH
stretching modes are visualized in the area 2957-2769 cmꢀ1. Hence,
the computational and experimental results are well comparable to
each other. Further, all these assignments are in harmony with the
results of literature as well [28]. It is obvious that an isopropyl
group or tert-butyl moiety usually gives distinctive band in the
symmetric CH3 bending region. In the case of compounds 1 and 2,
strong to weak bands observed at 1363e1325/1294 cmꢀ1 are
assigned to tert-butyl groups. The wave numbers resulted from
computational analysis, 1365e1330 and 1300/1292 cmꢀ1 are best
correlated with the experimental ones.
The linear regressions between the experimental and theoret-
ical wavenumbers obtained for compounds 1 and 2 are presented
in Supplementary Fig. S1. The minimal RMS (0.999) deviation
confirms the reliability of the assignments of the fundamental
modes of the compounds 1 and 2.
3.4. Analysis of Mulliken population
The vibrations of C]O stretching modes furnish characteristic
clear bands in the FT-IR, and the intensity of these clear bands could
be increased owing to either the formation of hydrogen bonds or
conjugation. Normally, the C]O stretching vibrations of carbalde-
hyde functionality are appears in the region 1760-1720 cmꢀ1 [30].
In the present experimental study, the aldehyde carbonylꢀs1tretch-
ing mode for compounds 1 and 2 are observed at 1693 cm while
the B3LYP calculations give this mode at 1692 and 1672 cmꢀ1. The
experimentally observed C]O stretching vibrations of
The atomic charges (total) of compounds 1 and 2 acquired by
Mulliken population analysis with DFT-B3LYP/6-311þþG(d,p)
method have been given in Table 2. Atomic charges have been
utilized to illustrate the process of equalization of electro negativity
and transfer of charge in chemical reactions [32]. The result shows
that most of the carbon atoms in the molecules (1 and 2) accom-
modate higher negative charges lead to a reorganization of electron
density. The carbon atoms such as C9, C12, C14, C15, C18, C21, C26
and C29, which are directly connected to the electronegative atoms,
Fig. 3. (a) UVeVis spectrum of compound 1 (b) Simulated UVeVis spectrum of compound 1 (c) UVeVis spectrum of compound 2 (d) Simulated UVeVis spectrum of compound 2.
Please cite this article in press as: K. Stalindurai, et al., Experimental and theoretical studies on new 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-
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K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
7
Fig. 4. HOMO-LUMO plots of compounds 1 and 2.
Table 4
molecules 1 and 2 in both vacuum as well as solvent phase have
been furnished in Table 3. The UVeVis spectra (experimental) of the
molecules 1 and 2 have been recorded in dichloromethane, ethanol
and hexane. Fig. 3 proves the calculated and experimental UVeVis
spectra of the molecules 1 and 2.
From Fig. 3, the observed two characteristic bands in the
wavelengths at ~400 and ~290 nm for all the three solvents
(dichloromethane, ethanol and hexane) have been assigned to n/
HOMO-LUMO energies of compounds 1 and 2.
Parameters (eV)
1
2
HOMO
LUMO
ꢀ6.7562
ꢀ5.2470
1.5092
ꢀ7.9233
ꢀ5.0838
2.8395
ꢀ8.3546
ꢀ4.1683
4.1863
ꢀ6.8667
ꢀ5.2590
1.6077
ꢀ7.8994
ꢀ5.0840
2.8154
ꢀ8.2901
ꢀ4.1825
4.1076
D
E
HOMO-1
LUMOþ1
D
E1
p
* and
absorption bands at ~ 400 nm in all the solvents are due to the
n/ * transition of the carbaldehyde functional moiety and the
later ones with strong intense band at ~290 nm are due to / p*
p / p* transitions of the molecules 1 and 2. The former
HOMO-2
LUMOþ2
D
E2
p
p
transitions of CZ and PTZ structural motifs. The absorption in-
tensities are slightly increased in non-polar solvents (Fig. 3). This
hyperchromic shift is probably due to neither hydrogen bonding
nor the nonpoints to the deprotonation of the compounds in the
hold elevated positive charge and as a result of the same, they
become greater acidic. Further, in both the compounds 1 and 2, the
positive charges are distributed on hydrogen atoms of the CZ and
PTZ moieties. The better symbolized graphical appearance of the
results is shown in Fig. 1.
solution state. The experimental lmax values and the computed
l
excitation wavelengths agree reasonably well above 300 nm.
3.5. UVeVis spectral analysis
3.6. Analysis of HOMO-LUMO
The method of TD-DFT with the basis set B3LYP/6-311þþG(d,p)
has been utilized to compute the UVeVis spectra of the molecules 1
and 2. The wavelengths, excitation energies, band gap energies and
oscillator strengths as well as the pertinent parameters of
The molecular orbitals (MOs) are significant quantum chemical
factors for the determination of interaction of a molecule with
other species and also for characterization of chemical reactivity,
global softness and hardness and, molecule's kinetic stability [33].
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8
K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
Fig. 5. Electron density and MEP with their contour of compounds 1 and 2.
Energy difference between LUMO and HOMO orbitals is one of the
vital factors for the determination of molecules' excitability; lesser
the energy, there is a decrease in the topological resonance energy
[34]. Here, six important molecular orbital energies have been
examined for compounds 1 and 2: the ground state, first and sec-
ond highest occupied and lowest unoccupied molecular orbitals
which are designated as HOMO, LUMO, HOMO-1, LUMOþ1, HOMO-
2, and LUMOþ2. Pictorial representations and related data of these
molecular orbitals are furnished in Fig. 4 and Table 4, respectively.
As per B3LYP/6-311þþG(d,p) calculation, the band-gap energies
the same have been resonated in the region of 7.8e6.8 ppm. The
carbaldehyde proton of both the molecules 1 and 2 is appeared in
the extreme downfield region of 9.8 ppm in the experimental
proton NMR due to the deshielding effect and this experimental
value is comparable with that of the chemical shifts of 1 and 2
resulted from the computational calculations. Further, signals for
alkyl functionalities such as n-butyl, n-hexyl, and di-tert-butyl of
both the molecules are obtained experimentally in the range of
4.0e0.9 ppm while the same resulted theoretically in the range of
4.2e0.8 ppm.
(DE) of the compounds 1 and 2 are about 1.5092 and 1.6077 eV. The
The experimental 13C chemical shift values of aromatic ring
carbons of CZ and PTZ structural motifs are obtained in the range
between 150 and 109 ppm and these values are comparable with
that of the results acquired from theoretical calculations. The
chemical shift of carbonyl carbon of the molecules 1 and 2 are
resonated experimentally at 190.00 and 190.02 ppm, respectively
while the same theoretically obtained at 193.03 and 193.15 ppm,
respectively by employing B3LYP method and these are comparable
to each other. In addition, the alkyl carbons resonated in the region
of 41-94-14.50 ppm and 48.30e14.05 ppm in the theoretical and
experimental 13C NMR, respectively. On the whole, experimental
and computational results of 1H NMR and 13C NMR of the molecules
1 and 2 imply that both the results are good to satisfactory when
compared to each other. On comparing the theoretical results,
slight variations noted in the experimental chemical shifts espe-
cially in the alkyl region are probably due to the effect of solvent,
concentration, and temperature.
HOMO's are localized largely on the PTZ moiety. At the same time,
the LUMO's are localized chiefly on carbaldehyde part on the PTZ
ring.
3.7. Molecular electrostatic potential (MEP) analysis
The electrostatic potential is a dominant tool which provides
insight to determine the reactive sites, intermolecular association
and physicochemical affairs and also interactions of hydrogen
bonding [35]. Electron density and model of electrostatic potential
of the molecules 1 and 2 (0.002 a.u isodensity surface computed)
are shown in Fig. 5. From the MEP pictures, it could be seen that the
isosurfaces ranges from ꢀ0.104 to þ0.104 kcal/mol with dark-blue
colour signifying exceedingly electron-poor regions and red-
colour denoting electron rich region. As seen from the figure, the
plausible reactive location of the molecules 1 and 2 are in support
of electrophilic-attack. The negative province is confined on the
area of oxygen atom of the carbaldehyde (O16) part of PTZ ring.
3.9. Non-linear optical characteristics
3.8. Nuclear magnetic resonance spectral analysis
For investigating the relationship between non-linear optical
properties (NLO) and molecular structures, the polarizabilities as
well as first order hyperpolarizabilities have been calculated. It is
recognized that molecules possessing superior dipole moment,
molecular polarizability and first hyperpolarizability show greater
The optimized structure of the studied molecules 1 and 2 is used
to calculate the proton and carbon NMR employing DFT-B3LYP/6-
311þþg(2d,p) method. The theoretical chemical shifts of both the
molecules are compared with their corresponding experimental
NMR data, summarized in Table 5. In the experimental proton NMR,
chemical shifts of aromatic ring protons are collectively resonated
in the region of 8.1e6.9 ppm while in the theoretical proton NMR,
non-linear optical behaviors [36]. The first hyperpolarizability (
b
)
and the hyperpolarizability components bx
,
by and bz of compounds
1 and 2 in addition to associated characteristics (m0, atotal, and a0
)
are provided in Table 6.
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K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
9
Table 5
NMR Chemical Shift of compounds 1 and 2.
Atom
1
2
Atom
1
2
Calc.
Expt.
Calc.
Expt.
Calc.
Expt.
Calc.
Expt.
H48/H50
H42/H44
H43/H45
H44/H46
H45/H47
H46/H48
H47/H49
H49/H51
H50/H52
H51/H53
H52/H54
H53/H55
H54/H56
H55/H57
H56/H58
H57/H59
H58/H60
H59/H61
H60/H62
H61/H63
H62/H64
H63/H65
H64/H66
H65/H67
H66/H68
H67/H69
H68/H70
H69/H71
H70/H72
H71/H73
H72/H74
H73/H75
H74/H76
H75/H77
H76/H78
H77/H79
H78/H80
H79/H81
H80/H82
H81/H83
9.64
6.77
7.30
7.49
7.09
7.17
7.04
7.11
7.24
7.85
7.81
7.31
7.12
1.08
1.57
1.14
1.56
1.55
1.37
1.12
1.51
1.19
1.68
1.66
1.23
1.57
1.05
1.27
1.37
1.04
1.35
3.61
3.67
2.05
2.06
1.42
1.44
1.29
0.98
1.00
e
9.82
8.12e6.97
9.58
6.84
7.34
7.74
7.21
7.30
7.02
7.15
7.28
7.78
7.81
7.21
7.12
1.55
1.41
1.56
1.03
1.13
1.63
1.04
1.34
1.32
1.58
1.05
1.20
1.12
1.53
1.22
1.60
1.35
1.61
4.24
3.76
1.97
1.39
1.07
1.85
1.04
1.21
1.24
1.32
9.81
8.13e6.94
C15
C1
C2
C3
C4
C5
C7
C8
C9
193.03
112.63
133.85
130.61
124.65
131.49
131.94
124.91
135.95
125.42
115.45
143.34
151.13
139.82
108.17
125.75
144.95
114.80
124.68
124.62
114.57
144.03
123.67
107.83
140.32
41.25
31.53
27.75
31.83
41.37
27.79
31.80
31.28
55.18
30.54
22.75
14.17
e
190.00
150.39e109.12
193.15
115.73
135.86
132.09
126.57
136.61
137.58
126.65
136.55
126.88
118.77
141.48
154.92
140.50
107.69
124.48
144.45
114.51
124.25
124.49
114.49
144.17
125.14
107.60
141.11
41.94
28.00
31.60
31.54
41.26
31.70
31.54
27.84
50.78
30.25
31.07
35.14
26.85
190.02
150.38e109.13
C10
C11
C12
C14
C18
C19
C20
C21
C22
C23
C24
C25
C26
C27
C28
C29
C30
C31
C32
C33
C34
C35
C36
C37
C38
C39
C40
C41
C42
C43
1.45
1.46
47.99e34.77
32.04e13.84
48.30e34.77
32.06e14.05
3.97e1.01
3.94e0.90
e
e
e
14.46
e
e
e
e
e/H84
e/H85
e/H86
e/H87
e
e
e
1.12
0.76
0.82
The calculated values of total dipole-moment and polarizability
of compounds 1 and 2 are found to be 6.871, 6.205 Debye and
6.223 ꢁ 10ꢀ23, 6.681 ꢁ 10ꢀ23 Debye-Ang, respectively. Neverthe-
less, the average value of polarizability of the synthesized com-
pounds 1 and 2 are larger than that of p-nitroaniline, a typical non-
linear optical material [37]. The degree of molecular hyper-
4. Conclusion
Two new heterocyclic molecules, 7-(3,6-di-tert-butyl-9H-car-
bazol-9-yl)-10-alkyl-10H-phenothiazine-3-carbaldehydes have
been synthesized by adopting Ullman type coupling as a key step.
Computational and experimental studies on the same have been
made. The parameters related to the molecular structure of the title
compounds are in good accord with the reported XRD results of
single crystal. The vibrational frequencies obtained experimentally
are compared with the theoretically calculated wave numbers and
are in harmony with each other. The small energy difference be-
tween the HOMO and LUMO of the title compounds enlighten the
happening of ultimate transfer of charge within the molecule. The
molecular orbitals, molecular electrostatic potential surface and
NLO analysis direct to the understanding of various properties of
the molecules synthesized. The synthesized molecules could be
utilized for the preparation of NLO crystals which might generate
second order harmonic waves.
polarizability (
b
) of compounds 1 and 2 are 3.641 ꢁ 10ꢀ30 and
3.205 ꢁ 10ꢀ30, respectively. Further, the first hyperpolarizability
values of the compounds 1 and 2 are compared with urea
(0.372 ꢁ 10ꢀ30 esu). The hyperpolarizability values (
b) of com-
pounds 1 and 2 are nearly nine times higher compared to urea [38].
In addition, the dipole-moments of compounds 1 and 2 are also
greater when compared with urea (1.373 Debye). The aforemen-
tioned results imply that the molecular polarizability as well as
hyperpolarizability of the synthesized compounds 1 and 2 in all
coordinates are active and hence they could be utilized for the
preparation of non-linear optical crystals which might generate
second order harmonic waves.
Please cite this article in press as: K. Stalindurai, et al., Experimental and theoretical studies on new 7-(3,6-di-tert-butyl-9H-carbazol-9-yl)-10-
alkyl-10H-phenothiazine-3-carbaldehydes, Journal of Molecular Structure (2016), http://dx.doi.org/10.1016/j.molstruc.2016.11.022

10
K. Stalindurai et al. / Journal of Molecular Structure xxx (2016) 1e11
geometry, Adv. Funct. Mater. 16 (2006) 1057e1066.
Table 6
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NLO properties of compounds 1 and 2.
1
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Dipole moment
mx
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4.604
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0.155
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6.205
ꢀ5.058
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Polarizability
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ꢀ259.912
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ꢀ285.478
6.681 ꢁ 10ꢀ23
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ꢀ255.484
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Hyperpolarizability
bxxx
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70.746
ꢀ201.511
63.588
ꢀ28.103
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55.231
66.037
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ꢀ119.298
3.641 ꢁ 10ꢀ30
3.205 ꢁ 10ꢀ30
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Acknowledgement
Financial assistance provided by the Department of Science and
Technology, New Delhi, India under Fast-Track Scheme [SR/FT/CS-
149/2011] is gratefully acknowledged.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.molstruc.2016.11.022.
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alkyl-10H-phenothiazine-3-carbaldehydes, Journal of Molecular Structure (2016), http://dx.doi.org/10.1016/j.molstruc.2016.11.022