Synthesis and DFT calculation on novel derivatives of Bis (indolyl) methanes

Article abstract of DOI:10.1016/j.molstruc.2016.04.082

Bis (indolyl) methane derivatives are an important class of biomolecules and heterocyclic scaffold of organic compounds. To extension novel Bis (indolyl) methane derivatives, two new aldehydes have been applied. In order to structural investigation, the optimized geometry, total energy, potential energy surface and vibrational wavenumbers of Bis (indolyl) methanes have been determined using DFT/B3LYP method with 6-31G (d) basis set. A complete vibrational assignment is provided for the observed IR spectra of Bis (indolyl) methanes. These methods are proposed as a tool to be applied in the structural characterization of Bis (indolyl) methanes. The isotropic chemical shift computed by ¹H and ¹³C NMR chemical shifts of the Bis (indolyl) methanes, calculated using the GIAO method, shows good agreement with experimental observations. The calculated HOMO and LUMO with frontier orbital gap are presented in order to predict antibacterial properties.

Full text of DOI:10.1016/j.molstruc.2016.04.082

Journal of Molecular Structure 1119 (2016) 404e412
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Synthesis and DFT calculation on novel derivatives of Bis (indolyl)
methanes
*
Maryam Zarandi , Alireza Salimi Beni
Department of Chemistry, Yasouj University, Yasouj, 75918-74831, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 December 2015
Received in revised form
Bis (indolyl) methane derivatives are an important class of biomolecules and heterocyclic scaffold of
organic compounds. To extension novel Bis (indolyl) methane derivatives, two new aldehydes have been
applied. In order to structural investigation, the optimized geometry, total energy, potential energy
surface and vibrational wavenumbers of Bis (indolyl) methanes have been determined using DFT/B3LYP
method with 6-31G (d) basis set. A complete vibrational assignment is provided for the observed IR
spectra of Bis (indolyl) methanes. These methods are proposed as a tool to be applied in the structural
characterization of Bis (indolyl) methanes. The isotropic chemical shift computed by 1H and C NMR
chemical shifts of the Bis (indolyl) methanes, calculated using the GIAO method, shows good agreement
with experimental observations. The calculated HOMO and LUMO with frontier orbital gap are presented
in order to predict antibacterial properties.
10 April 2016
Accepted 25 April 2016
Available online 29 April 2016
13
Keywords:
Bis (indolyl) methane
Aldehyde
Synthesis
Theory
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
applications. The inclusion of substituents new aldehydes leads to
the variation of charge distribution in the molecule, and conse-
In recent years, the synthesis of bis heterocycles with an
appropriate linker has attracted considerable academic attention
due to their special pharmacological properties. Versatile Bis
quently affects the structural, electronic and vibrational parame-
ters. One of the interesting field of academic research is synthesis
and theoretical investigation of structural parameter of different
organic and inorganic compound [17e19]. In order to importance
and vide range application, however, reports on the structure pa-
rameters and spectroscopic properties of Bis (indolyl) methanes are
interesting and demanding [20,21]. Therefore, in the present paper
we continue our research program on deep investigation of organic
compound [22e24]. By consideration of versatile application of Bis
(indolyl) methanes such as biological, corrosion inhibitor, sensor
and so on [25,26]; it has been undertaken to synthesis and the
theoretical approach of geometrical parameters, vibrational fre-
quencies, molecular electrostatic potential, NBO analyses and
HOMO, LUMO of two new derivatives of Bis (indolyl) methanes.
(
indolyl) methanes by symmetrical or unsymmetrical structures
contain aryl/alkyl groups are reported to be biologically important
1e4]. Bis (indolyl) methanes as cruciferous substances promote
estrogen metabolism and induce apoptosis in human cancer cells
5]. Also these compounds applied in colorimetric sensors and
[
[
chromogenic sensors [6]. Synthesis of new Bis (indolyl) methanes
derivatives is desirable due to their wide occurrence as natural
products and various biological activities. The simple and the
straightforward protocol for the synthesis of Bis (indolyl) methanes
is reaction of 1H-indole with aldehydes or ketones produces aza-
fulvenium salts that react further with a second 1H-indole mole-
cule to form bis(indol-3-yl)methanes [7]. Various synthetic
methods for preparation of Bis (indolyl) alkane derivatives have
been reported in the literature by reaction of indole with various
aldehydes and ketones [8e16].
2. Experimental
2.1. Chemicals and apparatus
The substituted new aldehyde derivatives are very promising
materials for future colorimetric sensors and chromogenic sensors
All solvents and other chemicals were reagent grade and used
without further purification. All chemicals were purchased from
Merck and SigmaeAldrich. Melting points were measured on an
1
13
electrothermal KSB1N apparatus. The H NMR (400 MHz) and
C
*
Corresponding author.
E-mail address: maryam.zarandi88@gmail.com (M. Zarandi).
NMR (100 MHz) were run on BrukerAvanceDPX-400 spectrometer
http://dx.doi.org/10.1016/j.molstruc.2016.04.082
022-2860/© 2016 Elsevier B.V. All rights reserved.
0

M. Zarandi, A. Salimi Beni / Journal of Molecular Structure 1119 (2016) 404e412
405
6
in DMSO-d solvent, with tetramethylsilane (TMS) as the standard
and J values are given in Hz. 2. Diameter of NMR tube was 5 mm.
The software that used for interpretation of peaks was ACD/NMR
Processor Academic Edition. FT-IR spectra were recorded in the
matrix of KBr with JASCO FT-IR-680 plus spectrometer. 6. The
program name of used for FT-IR analysis was spectra manager and
scale factors was 0.95. Reaction monitoring was accomplished by
TLC on silica gel polygram SILG/UV 254 plates. Mass spectra of the
products were obtained with a HP (Agilent technologies) 5937
Mass Selective Detector.
N
N
2
.1.1. Preparation of alumina sulfuric acid
In a 500 mL flask equipped by a dropping funnel and a gas inlet
HN
NH
HN
NH
Scheme 1. Chemical structure of BIM1 and BIM2.
tube for conducting HCl gas over adsorbing solution e.g. water.
Acidic Alumina (51 g, 510 mmol) was charged in the flask and
H
N
(a)
N
(
b)
(c)
N
N
O
HN
NH
O
N
(
b)
(
c)
N
N
HN
NH
ꢀ
ꢀ
Scheme 2. Synthetic routes of BIM1 and BIM2 (a) 1-Bromohexane, NaOH, DMSO, 110 C, overnight (b) POCl
C, 3 h.
3
, DMF, 95 C, overnight (c) Indole, Alumina sulphoric acid, Ethanol, 50
ꢀ
Fig. 1. The optimized structure and numbering of the tautomer of BIM1 and BIM2.

4
06
M. Zarandi, A. Salimi Beni / Journal of Molecular Structure 1119 (2016) 404e412
Table 1 (continued)
Table 1
Computed geometrical parameter for the ground state of BIM1 and BIM2 at DFT
method using 6e31 g (d) basis set.
Geometrical parameter BIM2
Geometrical parameter BIM1
C34C36N39C51
C34C36N39C40
N39C51C52H55
N39C41C40N39
42.0468
e
e
e
e
e
e
e
e
Geometrical parameter BIM2
Bond length(r)
Geometrical parameter BIM1
Bond length(r)
ꢁ136.8171
0.4099
C1eC2
1.4223 C1eC2
1.4223
0.3545
C1eC6
C1eC7
C7eC8
C7eC15
1.4058 C1eC6
1.4452 C1eC7
1.3724 C7eC8
1.4058
1.4453
1.3724
1.5155
1.5172
1.4459
1.3725
1.4061
1.5330
1.3801
1.3834
1.3799
1.3835
1.3916
1.3910
1.4526
1.0866
1.0804
1.1016
1.0865
1.0804
1.0962
1.0964
1.0981
1.0981
1.0077
1.0076
126.0792
127.6219
126.3108
127.4429
106.4305
120.3887
112.6385
106.4686
106.0786
129.3143
129.3029
0.43766
48.68336
48.61180
1.04043
ꢁ0.13790
96.92431
ꢁ156.24673
148.68133
ꢁ33.12108
0.92750
ꢁ1.00636
e
1.5156 C7eC15
chlorosulfonic acid (14 mL, 210 mmol) was added drop wise over a
period of 1 h at room temperature. HCl evolved immediately. After
completion of the addition, the mixture was stirred magnetically
for 1 h. Finally, a white solid material ASA was obtained (67 g) [27].
C15eC20
C16eC17
C17eC19
C17eC20
C20eC24
C15eC29
C29eC30
C29eC31
C30eC32
C31eC34
C32eC36
C34eC36
C40eC41
C40eC42
C51eC52
C51eC53
C2eN63
1.5172 C15eC20
1.4062 C17eC20
1.4224 C20eC24
1.4460 C16eC17
1.3724 C15eC29
1.5310 C2eN40
2.1.2. Preparation of 9-hexyl-9H-carbazole
1.4003 C8eN40
In a dried 100 mL round bottom flask, carbazole (0.20 g,
1.4006 C19eN39
1.3931 C24eN39
1.3928 C36eN38
1.4035 C42eN38
1.4035 C52eN38
1.4048 C6eH12
1.1 mmol) was dissolved in DMSO (3 mL) followed by the addition
of NaOH (0.40 g) and then drop wise addition of hexylbromide
ꢀ
(0.33 g, 1.01 mmol). The reaction mixture was then heated at 90 C
overnight. Water was added to the reaction and the product iso-
lated by filtration. The product was then washed thrice with 50 mL
water, dried over Na SO and concentrated. The pure product was
2 4
1.4046 C8eH13
1.4047 C15eH71
1.4047 C16eH41
1.3802 C24eH28
1.3831 C52eH54
1.3800 C52eH55
1.3833 C53eH57
1.4226 C53eH58
1.4215 N39eH27
1.4208 N40eH14
1.0867 C1C7C15
obtained after silica gel column chromatography (n-Hexane) as a
white solid [28].
C8eN63
ꢀ
White powder, yield: 85%, mp: 75e77 C.
C19eN62
C24eN62
C36eN39
C40eN39
C51eN39
C6eH12
2.1.3. Typical procedure for the preparation of 9-Hexyl-9H-
carbazole-3-carbaldehyde
In a dried 100 mL round bottom flask, Phosphorylchloride
(
1.55 mL, 1.25eq) was added drop wise to N,N-dimethylformamide
C8eH13
1.0804 C8C7C15
ꢀ
C16eH64
C24eH28
C30eH33
C31eH35
C32eH37
C34eH38
C41eH44
C42eH46
C52eH55
C53eH57
N62eH27
N63eH14
Bond Angles ()
C6C1C7
C1C6H12
C15C7C8
C7C8H13
H13C8N63
C8N63H14
C2N63H14
C7C15C20
C7C15H65
C29C15H65
C15C20C24
C15C20C17
N63C8H13
C36N39C51
C36N39C40
C40N39C51
H37C32C36
H38C34C36
H44C41C40
H46C42C40
H55C52C51
H57C53C51
C15C7C8H13
1.0865 C17C20C15
1.0804 C24C20C15
1.0865 C7C15H71
1.0881 C1C6H12
1.0856 C7C15C20
1.0856 C20C15H71
1.0854 C29C15H71
1.0852 C7C8H13
1.0853 C20C24H28
1.0853 C6C1C7C15
1.0077 C1C7C15H71
1.0077 C17C20C15H71
H13C8C7C15
134.0015 H28C24C20C15
120.4212 C31C29C15H71
127.6763 C30C29C15H71
129.3136 C42N38C52H55
120.6473 C36N38C52H54
125.1138 H47C44C42N38
125.5078 H37C34C36N38
(DMF, 0.88 mL, 1.15 eq) for 1 h at 0 C. The mixture was stirred and
N-(hexyl) carbazole (0.25 g, 1 mmol) added during 1 h at room
temperature. After standing for 5 h at 90 C, the mixture was
ꢀ
poured into iceewater (30 mL), stirred 5 h, and neutralized with
sodium hydroxide. The solution was extracted three times with
ethyl acetate and dried with Na SO . The solvent was removed
2 4
under reduced pressure. The residue was purified by silica gel
column chromatography (eluent: ethyl acetate/n-hexane ¼ 1:9).
ꢀ
Cream powder, Yield: 55%, mp: 70e74 C.
ꢁ1
IR (cm ): 3052, 2955, 2929, 2857, 2727, 1893, 1686, 1593, 1469,
383, 1352, 1339, 1329, 1240, 1177, 1135, 807, 765, 748 and 730.
1
1
6
H NMR (400 MHz, DMSO-d ) d (ppm): 10.06 (s, 1H), 8.77 (s, 1H),
8
.30 (d, J ¼ 8 Hz,1H), 7.79 (d, J ¼ 8 Hz,1H), 7.70 (m,1H), 7.55 (m,1H),
7.31 (t, J ¼ 8 Hz, 1H), 4.46 (t, J ¼ 8 Hz, 2H), 2.5 (DMSO-d6), 1.77 (m,
2H), 1.25 (m, 6H) and 0.87 (t, J ¼ 8 Hz, 3H).
13
6
C NMR (100 MHz, DMSO-d ) d (ppm): 13.7, 22, 26, 28.4, 30.9,
38.9 (DMSO-d6), 42.5, 109.7, 110.2, 120, 120.7, 122.11, 122.2, 124,
112.7629
106.5615
106.0691
127.5367
126.1983
120.6473
119.9251
119.9464
120.1187
119.4159
119.5268
119.4125
119.4538
119.3758
119.3193
1.2324
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
126.6, 126.7, 128.2, 140.4, 142.6 and 192.
e
e
e
2
.1.4. Preparation of 4-Diphenylamino benzaldehyde
-Diphenylamino-benzaldehyde was prepared by adopting
literature procedure [29].
e
4
e
e
e
e
2
.1.5. Typical procedure for the preparation of Bis (indolyl)
methanes
In a dried 100 mL round bottom flask, A mixture of benzalde-
e
e
e
e
hyde (1 mmol), indole (2 mmol), and ASA (0.04 g) was stirred
e
ꢀ
magnetically at 80 C with ethanol, and the progress of the reaction
e
was monitored by TLC. After completion of the reaction, in order to
work up the product, catalyst was separated by filtration. Water
was added and the product extracted into ethyl acetate. The organic
e
̊
C7C1C6H12
C1C7C15H65
C15C29C30H33
C15C20C24H28
C17C20C15H65
C32C36N39C40
1.1925
49.0590
2.2160
ꢁ0.2531
ꢁ23.0962
42.7369
e
e
e
2 4
layer was dried over anhydrous Na SO and then evaporated under
e
a vacuum to afford the crude product, which was further purified
by column chromatography. In all the cases, the product obtained
after the usual work up gave satisfactory spectral data.
e
e

M. Zarandi, A. Salimi Beni / Journal of Molecular Structure 1119 (2016) 404e412
407
1
Table 2
H NMR (400 MHz, DMSO-d6) & (ppm): 8.34 (d, J ¼ 1.2, 1H),
.15(d, J ¼ 4, 1H), 8.07 (m, 2H), 7.7 (d, J ¼ 8, 1H), 7.69 (d, J ¼ 8, 1H),
Thermodynamic data for the BIM1 and BIM2 in the gas phase calculated at DFT
method by using 6-31G (d) basis set.
8
7.55 (m, 4H), 7.48 (m, 2H), 7.17 (m, 4H), 6.87 (m, 2H), 6.70 (s, 2H),
Compound
Ea
Ha
Ga
4.49 (t, J ¼ 8, 2H), 2.5 (DMSO-d6), 1.83 (m, 2H), 1.30 (m, 6H), 0.81(t,
BIM2
BIM1
ꢁ1513.692399
ꢁ1517.276455
ꢁ1513.691455
ꢁ1517.275510
ꢁ1513.787688
ꢁ1517.377393
J ¼ 8, 3H).
13C NMR (100 MHz, DMSO-d6): 142.3, 141.0, 130.5, 130.4, 128.8,
126.8,124.8,122.8,122.7,121.3,121.1,120.8,120.0,116.5,110.2,109.9,
a
Total energies in Hartree.
85.7, 43.0, 38.9(DMSO-d6), 31.4, 29.0, 26.6, 22.5, 14.3.
Mass: m/z 495 (Mþ1), 494, 465, 394, 363, 334, 245, 219, 173 and
2
.1.6. 3-[Bis-(1H-indol-3-yl)-methyl]-9-hexyl-9H-carbazole (BIM1)
130.
ꢀ
Yield: 65%, solid, mp: 124e128 C.
ꢁ
1
IR (cm ): 3423, 2925, 1590, 1483, 1415, 1198, 1120, 745.
Fig. 2. Molecular electrostatic potential mapped on the isodensity surface of BIM1 and BIM2.
Table 3
Calculated and observed vibrational frequencies of BIM1 optimized by DFT method using 6-31G (d) basis set.
Entry
DFT
Exp.
Assignment
1
2
3
4
5
6
7
8
9
3670
3282
3423
ʋ
y
y
y
y
y
y
y
y
y
y
y
y
y
y
ʋ
N40-H14, N39-H27
C8-H13, C24-H28
3210, 3201, 3189, 3181
3208, 3198, 3178, 3278
3208, 3198
3201, 3196
3186, 3186
3181
3178
3178
C44-H47, C46-H50, C45-H49, C48-H51
C3-H9, C4-H10, C5-H11, C6-H12
C16-H41, C18-H22, C21-H25, C23-H26
C30-H33, C31-H35, C34-H37
C16-H41, C18-H22, C23-H26, y C3-H9, C5-H11, C6-H12
C44-H47, C45-H49,C46-H50, C48-H51
C3-H9, C4-H10, C5-H11, C6-H12
C16-H41, C18-H22, C21-H25, C23-H26
C31-H35, C34-H37
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
3178
3112
C65-H68, H69, H70
3107, 3043, 3041
3103, 3078, 3067,3057
3028, 3017, 3012
2987
1678, 1655
1676, 1677, 1634
1544, 1537, 1528, 1339
1348
1333, 1328
1247
1186
1044
1043
965
964
964
935
890, 889
759
C65-H69, H70, C64-H66, H67
C52-H54,H58, C53-H57, H58
C56-H60, H61,C64-H66, H67, C59-H62,H63
C15-H71
2925
ʋ Carbazole Ring
ʋ indole Ring
d
d
d
d
1590
1483
1415
C52-H54,C52-H55, C53-H57, C53-H58, C56-H60, C56-H61, C59-H62, C59-63, C64-H67,C64-H66, C65-H68, C65-H69, C65-H70
Ring Carbazole
Ring 1,2,3,4
C15-H71, C16-H41, C18-H22, C21-H25, C23-H26, C24-H28
1198
1120
d
H
Ring 1,3
Ring def. 2
Ring def. 3
t
t
t
t
C16-H41, C18-H22, C21-H25, C23-H26
C16-H41, C18-H22, C3-H9, C4-H10, C5-H11, C6-H12
C44-H47, C45-H49, C46-H50, C48-H51
C31-H35, C34-H37
rings def. 1,2,3,4
Carbazole Ring
745
t

408
M. Zarandi, A. Salimi Beni / Journal of Molecular Structure 1119 (2016) 404e412
2
(
.1.7. {4-[Bis-(1H-indol-3-yl)-methyl]-phenyl}-diphenyl-amine
BIM2)
Yield: 85%; solid, mp: 169e172 C.
selected as aromatic aldehyde. In order the synthesis of (BIM1) n
the first step; hexyl was introduced to carbazole in the presences of
NaOH and DMSO as solvent. In the next step 9-hexyl-9H-carbazole
undergoes VilsmeiereHaack reaction for formylation. Also triphe-
nylamine undergoes VilsmeiereHaack reaction for formylation. In
final synthetic protocol indole in the presence of alumina sulphoric
acid (ASA) (10% mol), ethanol, aromatic aldehydes were used for
preparation of Bis (indolyl) methans.
ꢀ
ꢁ1
IR (cm ): 3412, 3054, 2924, 2855, 2213, 1708, 1586, 1504, 1490,
456, 1414, 1334, 1092, 112, 853, 790, 742.
1
1
H NMR (400 MHz, DMSO-d6) & (ppm): 7.36 (d, J ¼ 8, 2H), 7.31
m, 4H), 7.24 (t, J ¼ 4, 4H), 7.04 (t, J ¼ 8, 4H), 6.99 (m, 2H), 6.96 (d,
J ¼ 8, 4H), 6.94 (m, 2H), 6.92 (s, 1H), 6.88 (m, 4H), 2.5(DMSO-d6).
(
13
C NMR (100 MHz, DMSO-d6:3.9): 147.8, 145.3, 140.4, 137.0,
31.1, 130.5, 129.9, 129.8, 127.1, 127.0, 124.4, 123.9, 123.7, 122.9, 121.3,
19.5, 118.6, 111.9, 38.9(DMSO-d6).
1
1
4.2. Geometry optimization and energies
Mass: m/z 490 (Mþ1), 489, 388, 274, 245, 203, 117 and 77.
The optimized molecular structure of Bis (indolyl) methans
along with numbering of atoms are shown in Fig. 1. The optimized
geometrical parameters of Bis (indolyl) methans obtained by
DFTeB3LYP/6-31G (d) are listed in Table 1. Comparison of the
theoretical bond lengths of two Bis (indolyl) methans indicates that
all bond length around C15 are equal roughly. These bonds include
C7-C8, C15-C20, C20-C24, C15-H65, C15-H71 and calculated bond
lengths at DFT/B3LYP level are 1.4452, 1.5172, 1.3724 and 1.1016 Å,
respectively.
3
. Computational details
Theoretical calculations were performed using GAUSSIAN 98
package and the Gauss-View molecular visualization program [30].
The geometries of (BIM1) and (BIM2) were optimized by using the
B3LYP method with the 6-31G (d) basis set.
In addition, we investigated the bond angles of Bis (indolyl)
methane molecules.
4
. Results and discussion
4.1. Synthesis
4.3. Thermodynamic properties
The molecular structures and synthetic routes of the (BIM1) and
(
BIM2) are represented in Schemes 1 and 2 respectively. Both of the
The dependence of Bis (indolyl) methanes thermodynamic
Bis (indolyl) methans have been synthesized by the stepwise syn-
thetic protocol. Every Bis (indolyl) methans contains two essential
parts include aldehyde and indoles. 9-Hexyl-9H-carbazole-3-
carbaldehyde and 4-diphenylaminobenzaldehyde have been
properties on the C15 substitutions was investigated. Thermody-
namic data for the BIM1 and BIM2 in the gas phase calculated at
DFT method by using 6-31G (d) basis set. Result are presented in
Table 2. It indicate all parameter E, H and G for BIM1 is higher in
Table 4
Calculated and observed vibrational frequencies of BIM2 optimized by DFT method using 6-31G (d) basis set.
Entry
DFT
Exp.
Assignment
1
2
3
4
5
6
7
8
9
3670
3670
3412
y
y
y
y
y
y
y
y
y
y
y
y
y
y
N62-H27, N63-H14
N63-H14
3283, 3283
3218, 3191
3218, 3190
3215,3215, 3206
3214, 3212
3209, 3188, 3179
3208, 3198, 3186
3199
C8-H13, C24-H28
C41-H44, C42-H46, C43-H48, C45-H49, C47-H49
C52-H55, C53-H57, C54-H59, C56-H60, C58-H61
C52-H55, C53-H57, C54-H59, C56-H60, C58-H61, C41-H44, C42-H46, C43-H48, C45-H49, C47-H49
C32-H37, C30-H33, C31-H35, C34-H38
C16-H64, C18-H22, C21-H25, C23-H26
C3-H9, C4-H10, C5-H11, C6-H12
10
11
12
13
14
15
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
3054
2924
2855
2213
1708
1586
1504
1490
1456
1414
C16-H54, C18-H22, C21-H25, C23-H26
C30-H33, C32-H37
3196
2987
C15-H65
1677, 1677, 1634
1669, 1657
1466
1461, 1459
1394
1388
1385
1372
1359
1358
1358
1147
1037
1016
987
972
966
Ring 1,2,3,4
Ring 5,6,7
d
y
y
H 5
Ring
N63-H12, N62-H27
C15-H65, C15-C20, C20-C17, C20-C24
Ring def. 1,2
Ring def. 3,4
d
H
H
Ring 6,7
Ring 1,2,3,4,5
1335
d
Ring def. 5,6
Ring def. 5,6,7
d
H
Ring
Twisting Ring
Twisting Ring 6.7
5
1092
1011
5
g
g
g
g
t
t
t
t
Ring 6
Ring 5
Ring 3
965
783
777
772
737
207
853
790
Ring 1
Ring 1.2
Ring 3.4
Ring 6.7
Ring 5
742
Twisting

M. Zarandi, A. Salimi Beni / Journal of Molecular Structure 1119 (2016) 404e412
409
Table 5
Experimental and calculated 1H NMR and 13C NMR chemical shifts (ppm) of BIM1.
Table 6
Experimental and calculated 1H NMR and13CNMR chemical shifts (ppm) of BIM2.
Proton
B3LYP/6-31G(d)
Exp.
Carbon
B3LYP/6-31G(d)
Exp.
Proton
B3LYP/6-31G(d)
Exp.
Carbon
B3LYP/6-31G(d)
Exp.
H9
6.65
6.65
6.52
7.00
6.02
6.19
6.65
6.65
6.65
6.13
5.71
7.51
7.20
6.82
7.07
6.65
7.37
6.91
6.65
3.75
3.75
1.57
1.57
1.26
1.26
1.15
1.15
1.26
1.26
0.87
0.67
0.67
5.71
7.55
7.55
7.17
7.70
6.87
7.17
7.48
7.48
7.55
6.87
6.70
8.34
8.15
7.55
7.69
7.17
8.07
8.07
7.17
4.49
4.49
1.83
1.83
1.30
1.30
1.30
1.30
1.30
1.30
0.81
0.81
0.81
6.70
C1
C2
C3
C4
C5
C6
C7
C8
113.32
120.54
110.26
108.46
105.99
106.64
107.97
110.26
35.16
107.06
113.35
105.97
120.22
120.54
108.41
95.87
110.26
122.5
108.00
114.25
110.66
94.35
124.55
125.60
110.33
94.04
107.27
111.46
105.50
36.67
126.8
130.4
122.7
121
110.2
116.5
120.0
122.7
85.7
120.0
126.8
110.2
130.4
130.4
120.8
109.9
122.7
130.5
120.8
128
122.8
109.9
141.0
142.3
122.8
109.9
120.0
124.8
110.2
43
H9
6.65
6.65
6.65
7.07
5.88
6.12
6.65
6.65
6.65
6.21
5.88
6.65
7.00
6.47
6.65
6.65
6.47
6.65
6.65
6.41
6.65
6.65
6.65
6.65
6.47
7.00
5.43
6.99
6.97
6.97
7.36
6.88
6.88
6.97
6.97
6.99
6.88
6.88
7.36
7.36
6.96
6.96
7.24
7.04
7.31
7.31
6.94
7.24
7.04
7.31
7.31
6.94
7.36
6.92
C1
C2
C3
C4
C5
C6
C7
C8
113.13
120.40
95.95
108.55
106.10
106.65
107.27
109.90
34.96
107.14
113.17
106.13
120.18
108.57
95.98
109.71
125.78
116.38
116.90
111.28
111.65
132.55
134.09
110.46
110.93
115.00
115.33
108.14
127.1
137.0
111.9
121.3
118.2
118.2
119.2
122.9
85.7
119.2
129.8
118.2
137.0
121.3
111.9
122.9
140.4
131.1
131.1
124.4
127
H10
H11
H12
H13
H14
H22
H25
H26
H27
H28
H33
H35
H37
H41
H47
H49
H50
H51
H54
H55
H57
H58
H60
H61
H62
H63
H66
H67
H68
H69
H70
H71
H10
H11
H12
H13
H14
H22
H25
H26
H27
H28
H33
H35
H37
H38
H44
H46
H48
H49
H50
H55
H57
H59
H60
H61
H64
H65
C15
C16
C17
C18
C19
C20
C21
C23
C24
C29
C30
C31
C32
C34
C36
C42
C43
C44
C45
C46
C48
C52
C53
C56
C59
C64
C15
C16
C17
C18
C19
C21
C23
C24
C29
C30
C31
C33
C34
C36
C40
C41
C42
C43
C45
C47
145.3
147.8
123.7
123.9
129.9
130.5
121.3
e
e
e
e
e
e
e
C51
C52
C53
C54
C56
C58
134.35
110.95
110.86
115.30
115.09
108.24
147.8
123.9
123.7
130.5
129.9
121.3
24.12
23.20
26.94
19.06
29
22.6
31.4
22.5
e
e
C65
8.78
14.30
comparison to other Bis (indolyl) methanes. The E value is
1517.276455 and ꢁ1513.692399 for BIM1 and BIM2 respectively.
frequencies in the infrared spectrum of compound are compared by
the experimental frequencies in Tables 3 and 4
ꢁ
4.4. Molecular electrostatic potential
4.5.1. N-H vibrations
In all the heterocyclic compounds, the NH stretching vibrations
ꢁ
1
Electrostatic potential maps, also known as electrostatic po-
occur in the region 3500e3000 cm [31]. The N-H stretching vi-
ꢁ1
tential energy maps, or molecular electrical potential surfaces,
illustrate the charge distributions of molecules three dimensionally.
These maps allow us to visualize variably charged regions of a
molecule. Knowledge of the charge distributions can be used to
determine how molecules interact with one another. In order to
understand the roles of the different groups substituted at the C15-
position by manipulation of the heterocyclic ring, we compared the
respective molecular electrostatic potential maps derived by mo-
lecular orbital calculations. Potential increases in the order
blue > green > yellow > orange > red. Electrostatic potential maps
of BIM1 and BIM2 are presented in Fig. 2. The positive (blue color)
were related to nucleophilic reactivity. It shows that the positive
regions are mainly over NH groups in indole rings. It indicates the
both molecules have nucleophilic reactivity mainly and substituted
groups in C15 do not differ charge distributions significantly.
bration is calculated to be 3669e70 cm and observed as high
intense peak at 3412e23 cm in the IR spectrum.
ꢁ
1
4.5.2. C-H vibrations
CeH stretching frequencies appear in the range of
in aromatic compound and in the range of
2850e3000 cm in aliphatic. The observed frequency value 3053
(aromatic units) and 2855e2924 cm (C15-H) are in
agreement with values in the range of 3282e3012 and 2938 of
B3LYP/6-31G (d) method. Also C-H stretching frequencies of hexyl
moiety observed in the range of 3012e3112 cm . The theoretically
calculated vibrations corresponding to C-H stretch show good
agreement with the experimentally observed vibrations.
ꢁ
1
3100e3000 cm
ꢁ1
ꢁ1
ꢁ1
of cm
ꢁ1
4.5.3. C-C vibrations
ꢁ
1
The bands between 1620 and 1680 cm and 1500-1700 in ar-
omatic compounds are usually assigned to C]C stretching and
bending frequencies respectively. The C]C stretching vibrations of
the Bis (indolyl) methanes are found in the range of
4
.5. Assignments of vibrational frequencies
One of the most useful tool for the identification of functional
ꢁ1
ꢁ1
groups of organic compounds, studies on molecular conformation
and reaction kinetics is application of vibrational spectroscopy. The
vibrational frequencies and also approximate description of each
normal vibrational mode obtained using DFT/B3LYP method with
1707e2212 cm in FT-IR for BIM1 and 1590 cm for BIM2. DFT
ꢁ
1
predict values in the range of 1657e1677 and 1633e1678 cm for
title compounds respectively. Also in-plane bending vibration
observed around 1414 and 1335 for BIM1 and BIM2 respectively.
ꢁ1
6
-31G (d) basis set are given in Tables 3 and 4. The observed band
Theoretical results predict values in the range of 1327e1466 cm

410
M. Zarandi, A. Salimi Beni / Journal of Molecular Structure 1119 (2016) 404e412
Fig. 3. Patterns of the principle highest occupied and lowest unoccupied molecular orbitals of BIM1 and BIM2 obtained with DFT/6-31 G (d) method.
Table 7
Some of the calculated energy values of BIM1 and BIM2 in their ground state with
singlet symmetry.
hydrogen atoms attached to the carbon atom and 2 hydrogen atom
attached to the nitrogen atoms. In the H NMR spectra just one of
aliphatic protons appears at 6.7 ppm as a singlet, because of H71 is
connected to four aromatic rings. The chemical shift value of H71
has been observed at 5.71 ppm at DFT method. The chemical shift
value for all aromatic hydrogen has been observed around
1
Compound
HOMO (a.u.)
LUMO (a.u.)
HOMO-LUMO gap, DE (a.u.)
BIM2
BIM1
ꢁ0.17812
ꢁ0.18704
ꢁ0.00956
ꢁ0.02109
0.16856
0.16595
6.82e8.24 and 6.13e7.51 ppm experimentally and at DFT method
respectively. Also all aliphatic hydrogens show chemical shift
around 0.81e4.49 and 0.67e3.27. As shown in Fig. 1, the studied
molecule has 35 different carbon atoms, which is consistent with
the structure based on molecular symmetry. The chemical shift
value of C15 which is in bonded to four aromatic rings have been
observed at 85.7 and 35.16 ppm experimentally and at DFT/6-
for in-plane bending vibrations. The theoretically computed fre-
quencies using B3LYP/6-31 G (d) method are assigned for CeC and
C]C stretching vibrations approximately coincides with FT-IR.
4.6. NMR spectra
31G(d) respectively. The experimental and theoretical values ob-
tained around 14.30e43 and 8.78e36.67 ppm respectively for other
aliphatic carbons. The agreement between the experimental and
calculated data is satisfactory.
The GIAO method is one of the most common approaches for
13
calculating isotropic nuclear magnetic shielding tensors. GIAO
C
NMR and 1H NMR chemical shifts calculations of the title com-
pounds were carried out by using B3LYP/functional with 6-31G (d)
basis set. Chemical shifts were reported in parts per million relative
Compound BIM2: This molecule has 26 hydrogen atoms in the
aromatic ring and one aliphatic hydrogen atom. 25 hydrogen atoms
attached to the carbon atom and 2 hydrogen atoms attached to the
1
13
1
to TMS for H and C NMR spectra. Experimental and calculated H
NMR and 13C NMR chemical shifts (ppm) of BIM1 and BIM2 are
presented in Tables 5 and 6.
1
nitrogen atoms. In the H NMR spectra just one of aliphatic protons
appears at 6.92 ppm as a singlet, because of H65 is bonded to three
aromatic rings. The chemical shift value of H65 has been observed
at 5.43 ppm at DFT method. The chemical shift value for all
Compound BIM1: The studied molecule has 17 hydrogen atoms
in the aromatic ring and 14 hydrogen atoms in aliphatic parts. 29

M. Zarandi, A. Salimi Beni / Journal of Molecular Structure 1119 (2016) 404e412
411
Table 8
carbon atoms, which is consistent with the structure based on
molecular symmetry. The chemical shift value of C15 which is in
bonded to three aromatic rings have been observed at 85.7 and
Calculated NBO charges on atoms of Bis (indolyl) methanes in the gas phase.
Atom no.
BIM1
Atom no.
BIM2
3
4.96 ppm experimentally and at DFT respectively, using 6-31G(d)
C1
C2
C3
C4
C5
C6
C7
C8
ꢁ0.087
0.159
C1
C2
C3
C4
C5
C6
C7
C8
ꢁ0.088
0.159
basis set. Similar to previous compound the experimental and
theoretical values for aromatic carbons of BIM2 is in the range of
ꢁ0.268
ꢁ0.249
ꢁ0.258
ꢁ0.249
ꢁ0.106
ꢁ0.023
ꢁ0.279
ꢁ0.216
ꢁ0.091
ꢁ0.259
0.157
ꢁ0.162
ꢁ0.241
ꢁ0.248
ꢁ0.050
ꢁ0.199
ꢁ0.216
ꢁ0.077
ꢁ0.272
0.118
ꢁ0.267
ꢁ0.240
ꢁ0.258
ꢁ0.215
ꢁ0.107
ꢁ0.022
ꢁ0.281
ꢁ0.216
ꢁ0.092
ꢁ0.259
0.157
ꢁ0.240
ꢁ0.269
ꢁ0.022
ꢁ0.037
ꢁ0.221
ꢁ0.218
ꢁ0.245
ꢁ0.245
0.143
95.5e134.35 and 111.9e147.8 ppm respectively. Also the agreement
between the experimental and calculated data is satisfactory.
4.7. HOMO and LUMO analyses
C15
C16
C17
C18
C19
C20
C21
C23
C29
C30
C31
C32
C34
C36
C42
C43
C44
C45
C46
C48
C52
C53
C56
C59
C64
C65
H9
H10
H11
H12
H13
H14
H22
H25
H26
H27
H28
H33
H35
H37
H41
H47
H49
H50
H51
H54
H55
H57
H58
H60
H61
H62
H63
H66
H67
H68
H69
H70
H71
N38
N39
N40
C15
C16
C17
C18
C19
C21
C23
C24
C29
C30
C31
C32
C34
C36
C40
C41
C42
C43
C45
C47
C51
C52
C53
C54
C56
C58
H9
H10
H11
H12
H13
H14
H22
H25
H26
H27
H28
H33
H35
H37
H38
H44
H46
H48
H49
H50
H55
H57
H59
H61
H64
H65
H68
N39
N62
N63
e
On the base of frontier molecular orbital theory, HOMO and
LUMO are acronyms for highest occupied molecular orbital and
lowest unoccupied molecular orbital, respectively. The energy dif-
ference between the HOMO and LUMO is termed the HOMO-
eLUMO gap. HOMO and LUMO are sometimes referred to as
frontier orbitals. The gap between the HOMO and LUMO energy
levels of the molecule is a tool for reactivity determination of the
molecule. As it decreases, the reactivity of the molecule increases
leading to a decrease in the stability of the molecule. The atomic
orbital compositions of the Frontier molecular orbital are shown in
Fig. 3. In BIM2 molecule, the
p nature is delocalized over the whole
0.185
0.159
triphenyl amine rings and indole rings slightly and the HOMO is
located over just triphenyl amine rings. For 3 BIM1, In the HOMO,
the charge density is mainly accumulated on the carbazole and
some part of indole rings and LUMO more charge density moves to
carbazole rings.
The HOMOeLUMO energy gap of Bis (indolyl) methans is
calculated at B3LYP/6-31G levels and are shown in Table 7.
HOMOeLUMO energy gap explains the eventual charge transfer
interaction within the molecule, which influences the biological
activity of the molecule. Molecular orbital theory, HOMO and LUMO
can elucidate bioactivity of compounds. The interaction between
ꢁ0.082
ꢁ0.279
ꢁ0.202
ꢁ0.226
ꢁ0.263
ꢁ0.245
ꢁ0.462
ꢁ0.455
ꢁ0.451
ꢁ0.452
ꢁ0.673
0.232
0.233
0.233
0.287
0.243
0.428
0.233
0.233
0.232
0.428
0.243
0.244
0.235
0.234
0.248
0.234
0.236
0.235
0.235
0.237
0.236
0.235
0.136
0.226
0.226
ꢁ0.246
ꢁ0.251
ꢁ0.226
ꢁ0.224
ꢁ0.252
0.151
ꢁ0.252
ꢁ0.252
ꢁ0.225
ꢁ0.226
ꢁ0.252
0.232
0.234
0.233
0.237
0.243
0.429
0.234
0.234
0.232
0.429
0.242
0.245
0.236
0.247
0.247
0.246
0.246
0.236
0.248
0.235
0.247
0.244
0.237
0.235
0.241
these molecules and the receptor of bacteria is dominated by pep
interaction among these frontier molecular orbitals [20]. Therefore
it is predicted that in In BIM2, all triphenyl amine and partially parts
of indole rings participate in bioactivity of compounds. BIM1
showed different participation; both carbazole and indole rings
have significant effect.
4.8. NBO analyses
NBO is a calculated bonding orbital with maximum electron
density. Natural (localized) orbitals are used in to calculate the
distribution of electron density in atoms and in bonds between
atoms. Therefore NBO calculations can provide the detailed insight
into the electronic structure of molecule. They have the
“maximum-occupancy character” in localized 1-center and 2-
center regions of the molecule. Natural bond orbital analyses pro-
vides an efficient method for determination of electron donor
orbital, acceptor orbital and the interacting stabilization energy
resulted from the second-order micro-disturbance theory. NBO
analysis has been performed on the Bis (indolyl) methans at the
B3LYP/6-31G (d) level in order to elucidate, the intra-molecular
rehybridization and delocalization of electron density within the
molecules. The calculated value of NBO charges using natural
population analysis (NPA) of optimized structures of Bis (indolyl)
methans are given in Table 8. It can be seen that, in BIM1, C65 and
N40 and in BIM2, N62 and N63 have the most negative charges.
Compound BIM1: The magnitudes of charge on carbon atoms
are changing between ꢁ0.673 and 0.185 at the B3LYP/6-31G (d)
level. This molecule has some carbons, which binding to nitrogen
atoms and these carbons have positive charge. In this molecule
there are three nitrogen atoms that have negative charge, the
charge values for N38, N39 and N40 are ꢁ0.391, ꢁ0.561 and ꢁ0.561
0.226
0.226
0.226
0.226
0.232
0.255
0.255
0.262
ꢁ0.391
ꢁ0.561
ꢁ0.561
0.263
0.235
ꢁ0.447
ꢁ0.561
ꢁ0.560
e
e
e
e
e
aromatic hydrogen has been observed in the range of 6.88e7.36
and 5.88e7.07 ppm experimentally and at DFT method respec-
tively. As shown in Fig. 1, the studied molecule has 35 different

412
M. Zarandi, A. Salimi Beni / Journal of Molecular Structure 1119 (2016) 404e412
0
at B3LYP/6-31G (d) level of calculation, respectively. The magni-
tudes of the hydrogen atomic charges are found to be positive at the
basis sets. The magnitude of the hydrogen atomic charges are ar-
ranged in an order from 0.136 to 0.428 at B3LYP/6-31G (d) method.
The two hydrogen atoms, H14 and H27 which have binding to ni-
trogen have more positive charge than other hydrogen atoms. H14
and H27 hydrogens bonded to atoms with same electronegativity.
Therefore charge value for these atoms is equal. The charge values
for H14 and H27 are 0.428 at B3LYP/6-31G (d) level of calculation,
respectively.
[5] X. Ge, S. Yannai, G. Rennert, N. Gruener, F.A. Fares, 3,3 -Diindolylmethane
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[
6] X. He, S. Hu, K. Liu, Y. Guo, J. Xu, S. Shao, Oxidized Bis(indolyl)methane: a
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[8] A. Maiti, P. Bhattacharyya, Montmorillonite clay-catalysed synthesis of Bis
(
(
indol-3-yl)-methanes and 1, 2-Bis (indol-3-yl) ethanes, J. Chem. Res. 11
1997) 424e425.
[
2 3 2
9] M. Rekha, H.R. Manjunath, N. Nagaraju, Mn/Al O and Mn/ZrO as selective
catalysts for the synthesis of bis (indolyl) methanes: the role of surface acidity
and particle morphology, J. Ind. Eng. Chem. 19 (2013) 337e346.
10] M.A. Zolfigol, P. Salehi, M. Shiri, A. Sayadi, A. Abdoli, H. Keypour, M. Rezaeivala,
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tri(bis(indolyl) methanes) as new triarylmethanes, Mol. Divers 12 (2008)
Compound BIM2:
[
[
5
. Conclusions
203e207.
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dolyl)methanes catalyzed by ABS in aqueous media under ultrasound irradi-
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[12] S. Khaksar, S.M. Ostad, Pentafluorophenylammonium triflate as an efficient,
environmentally friendly and novel organocatalyst for synthesis of bis-indolyl
methane derivatives, J. Fluor. Chem. 132 (2011) 937e939.
13] Z. Xiang, Z. Liu, X. Chen, Q. Wu, X. Lin, Biocatalysts for cascade reaction:
porcine pancreas lipase (PPL)-catalyzed synthesis of bis(indolyl)alkanes,
J. Amino Acids 45 (2013) 937e945.
14] F. Shirini, N. Ghaffari Khaligh, O. Goli Jolodar, An efficient and practical syn-
thesis of bis(indolyl)methanes catalyzed by N-sulfonic acid poly(4-
vinylpyridinium) chloride, Dyes Pigments 98 (2013) 290e296.
15] A. Khalafi-Nezhad, A. Parhami, A. Zare, A.R. Moosavi Zare, A. Hasaninejad,
F. Panahi, Trityl chloride as a novel and efficient organic catalyst for room
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tions in neutral media, Synthesis 4 (2008) 617e621.
In the present work, we have synthesized and calculated the
thermodynamic properties, geometric parameters, vibrational fre-
quencies, 13C and H NMR chemical shifts, Molecular electrostatic
potential, HOMO-LUMO levels and NBO analysis of the two novel
Bis (indolyl) methans derivatives BIM1 and BIM2 by using B3LYP
method with 6-31G (d) basis set. The calculated vibrational modes
assigned to their experimental values. It has been observed that all
scaled frequencies are in good agreement with experimental
values. The effect of substituents new aldehydes has been studied
to the variation of charge distribution in the molecule, and conse-
quently affects the structural, electronic and vibrational parame-
ters. HOMO and LUMO analyses revealed these compounds may
1
[
[
[
[
[
16] P. Pratim Kaishap, C. Dohutia, Synthetic approaches for Bis (indolyl) methanes,
I. J.P.S.R. 4 (2013) 1312e1322.
17] A. Panitsiri, S. Tongkhan, W. Radchatawedchakoon, U. Sakee, Synthesis and
anion recognition studies of novel bis (4-hydroxycoumarin) methane azo
dyes, J. Mol. Struct. 1107( (2016) 14e18.
have bioactivity due to pep interaction in all triphenyl amine and
partially parts of indole rings of BIM2 and carbazole and indole
rings in BIM1. NBO calculation indicates in BIM1, C65 and N40 and
in BIM2, N62 and N63 have the most negative charges.
_
[
[
[
18] S. Eryılmaz, M. Gül, E. Inkaya, M. Ta s¸ , Isoxazole derivatives of alpha-pinene
isomers: synthesis, crystal structure, spectroscopic characterization (FT-IR/
NMR/GCeMS) and DFT studies, J. Mol. Struct. 1108 (2016) 209e222.
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20] G.S. Suresh Kumar, A. Antony Muthu Prabu, S. Jegan Jenniefer, N. Bhuvanesh,
P. Thomas Muthiah, S. Kumaresan, Syntheses of phenoxyalkyl esters of 3,30-
bis(indolyl)methanes and studies on their molecular properties from single
crystal XRD and DFT techniques, J. Mol. Struct. 1047 (2013) 109.
21] S.Y. Ebrahimipour, H. Khabazadeh, J. Castro, I. Sheikhshoaie, A. Crochet,
M. Katharina, Fromm, cis-Dioxido-molybdenum(VI) complexes of tridentate
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Acknowledgement
The authors express their appreciation to the Graduate School
and Research Council of the Yasouj University for financial support
of this work.
Abbreviations
[
ASA
Alumina Sulfuric Acid
BIM2
{4-[Bis-(1H-indol-3-yl)-methyl]-phenyl}-diphenyl-
amine
52e61.
[22] A.S. Salimi Beni, A.N. Chermahini, H. Sharghi, S.M. Monfared, MP2, DFT and ab
initio calculations on thioxanthone, Spectrochim. Acta A 82 (2011) 49e55.
23] A. Salimi Beni, S. Mirzaei Monfared, DFT and MP2 calculations on new series of
BIM1
DFT
3-[Bis-(1H-indol-3-yl)-methyl]-9-hexyl-9H-carbazole
Density Functional Theory
[
hydroxythioxanthones, J. Mol.Struct. 1039 (2013) 8e21.
DMSO Dimethyl Sulfoxide
HOMO Highest Occupied Molecular Orbital
LUMO Lowest Unoccupied Molecular Orbital
[24] A. Salimi Beni, Z. Dalirnasab, A. Teimouri, A. Najafi Chermahini, Studies on
tautomerism in the triazoline dione, Can. J. Chem. 89 (2011) 1387e1395.
0
[
25] N. Wang, X. Liang, Q. Li, Y. Liaoab, S. Shao, Nitro-substituted 3,3 -bis(indolyl)
methane-modified silica gel as a sorbent for solid-phase extraction of flavo-
noids, RSC Adv. 5 (2015) 15500e15506.
GIAO
NBO
NMR
TLC
Gauge Invariant Atomic Orbital
Natural Bond Orbital
Nuclear Magnetic Resonance
Thin layer Chromatography
[26] P. Praveen, P.S. Parameswaran, M.S. Majik, Bis(indolyl)methane alkaloids:
Isolation, bioactivity, and syntheses, Synthesis 47 (2015) 1827e1837.
[
[
27] S. Besoluk, M. Kucukislamoglu, M. Nebioglu, M. Zengin, M. Arslan, Solvent-free
synthesis of dihydropyrimidinones catalyzed by alumina sulfuric acid at room
temperature, J. Iran. Chem. Soc. 5 (2008) 62e66.
28] A. Salimi Benia, M. Zarandia, A.R. Madram, Y. Bayat, A. Najafi Chermahini,
R. Ghahary, Synthesis and characterization of organic dyes bearing new
electron-withdrawing group for dye-sensitized solar cells, Electrochim. Acta
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