Novel copper(II) and zinc(II) complexes of halogenated bidentate N,O-donor Schiff base ligands: Synthesis, characterization, crystal structures, DNA binding, molecular docking, DFT and TD-DFT computational studies

Article abstract of DOI:10.1016/j.ica.2020.120004

Eight novel complexes, including: [Cu(L¹)₂]: C1, [Cu(L²)₂]: C2, [Cu(L³)₂]: C3, [Cu(L⁴)₂]: C4, [Zn(L¹)₂]: Z1, [Zn (L²)₂]: Z2

Full text of DOI:10.1016/j.ica.2020.120004

Journal Pre-proofs
Research paper
Novel copper(II) and zinc(II) complexes of halogenated bidentate N,O-donor
Schiff base ligands: Synthesis, characterization, crystal structures, DNA bind‐
ing, molecular docking, DFT and TD-DFT computational studies
Hadi Kargar, Reza Behjatmanesh-Ardakani, Vajiheh Torabi, Asiyehalsadat
Sarvian, Zahra Kazemi, Zahra Chavoshpour-Natanzi, Valiollah Mirkhani,
Atefeh Sahraei, Muhammad Nawaz Tahir, Muhammad Ashfaq
PII:
DOI:
Reference:
S0020-1693(20)31204-4
https://doi.org/10.1016/j.ica.2020.120004
ICA 120004
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
10 July 2020
2 September 2020
4 September 2020
Please cite this article as: H. Kargar, R. Behjatmanesh-Ardakani, V. Torabi, A. Sarvian, Z. Kazemi, Z.
Chavoshpour-Natanzi, V. Mirkhani, A. Sahraei, M. Nawaz Tahir, M. Ashfaq, Novel copper(II) and zinc(II)
complexes of halogenated bidentate N,O-donor Schiff base ligands: Synthesis, characterization, crystal
structures, DNA binding, molecular docking, DFT and TD-DFT computational studies, Inorganica Chimica Acta
(2020), doi: https://doi.org/10.1016/j.ica.2020.120004
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Authors' statement
We would like to make an statement about the author's main contribution: HK and AS
synthesized all the compounds, and characterized them by different techniques; RBA and VT
designed the model and the computational framework and analysed the data.; ZK, ZCN and
VM were responsible for biological data acquisition and analysis; AS and MNT collected the
single-crystal X-ray diffraction data and determined the structures. HK wrote the manuscript
with input from all authors. All authors discussed the results and commented on the
manuscript.
Compliance with ethical standards
Conflict of interest: The authors declare that they have no conflict of interest.
Graphical abstract
The synthesis, crystal structures, DFT calculations, DNA binding and molecular docking of a
series of Cu(II) and Zn(II) complexes bearing halogenated bidentate N,O-donor Schiff base
ligands have been reported.
Molecular docking
Crystal structure
DFT calculation

Br
O
N
N
O
F
Zn
F
Br
DNA binding
Highlights
 Synthesis of halogenated bidentate N,O-donor Schiff base metal complexes.
 Characterization of synthesized compounds using various spectroscopic
techniques.
 Structural and DFT studies of the new Cu(II) and Zn(II) complexes.
 The interaction of ligands and complexes with DNA.
 Investigation of DNA binding and molecular docking propensity of synthesized
compounds.

Novel copper(II) and zinc(II) complexes of halogenated bidentate N,O-
donor Schiff base ligands: Synthesis, characterization, crystal structures,
DNA binding, molecular docking, DFT and TD-DFT computational studies
Hadi Kargar a,*, Reza Behjatmanesh-Ardakani b, Vajiheh Torabi b, Asiyehalsadat Sarvian b,
Zahra Kazemi c, Zahra Chavoshpour-Natanzi c, Valiollah Mirkhani c, Atefeh Sahraei d,
Muhammad Nawaz Tahir e, Muhammad Ashfaq e
a Department of Chemical Engineering, Faculty of Engineering, Ardakan University, P.O.
Box 184, Ardakan, Iran.
b Department of Chemistry, Payame Noor University, 19395-3697 Tehran, Iran
c Department of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran
d Zahedan University of Medical Sciences, Zahedan, Iran
e Department of Physics, University of Sargodha, Punjab, Pakistan
Abstract: Eight novel complexes, including: [Cu(L1)2]: C1, [Cu(L2)2]: C2, [Cu(L3)2]: C3,
[Cu(L4)2]: C4, [Zn(L1)2]: Z1, [Zn (L2)2]: Z2, [Zn (L3)2]: Z3, and [Zn (L4)2]: Z4, with four
bidentate N,O-donor halogenated bis-Schiff base ligands (HL1: 4-Bromo-2-[(4-
fluorophenylimino) methyl]phenol; HL2: 4-Bromo-2-[(4-chlorophenylimino)methyl]phenol;
HL3:
4-Bromo-2-[(4-bromophenylimino)
methyl]phenol;
HL4:
4-Bromo-2-[(4-
iodophenylimino)methyl]phenol) were synthesized and their structures were proved by SC-
1
XRD, FT-IR, UV-Vis, and H NMR spectroscopic techniques. The single crystal X-ray
diffraction analysis reveals that a distorted tetrahedral geometry is formed in zinc complex
whereas a slightly distorted square planar geometry is formed in both copper(II) complexes
* Corresponding authors: e-mail:h.kargar@ardakan.ac.ir; hadi_kargar@yahoo.com

of C3 and C4. Theoretical calculations of the complexes were carried out via DFT as well as
TD-DFT using B3LYP method employing the Def2-TZVP basis set, where the calculation
results are in accordance with the experimental results. NBO analysis has been used to
elucidate charge transfer information of the Z1, C3 and C4 complexes. Moreover, interaction
of ligands and complexes with FS-DNA was assessed using UV-Vis spectroscopy as well as
molecular docking. The experimental and theoretical results reveal that the DNA-binding
affinity of as-prepared complexes increases with decreasing in electronegativity of substituted
halogen atom.
Keywords: Schiff base complex, Single crystal x-rays diffraction, Theoretical calculation,
DNA-binding, Molecular docking
1. Introduction
Schiff base ligands prepared from salicylaldehyde and aniline followed by their metal
complexation have been widely reported over the last few years. They can act as bidentate
ligands for some divalent transition metals like zinc and copper [1-6]. Generally, a C=N
(iminic group) has a high affinity towards metal ions coordination such as zinc and copper
[7]. The coordination chemistry of zinc and copper complexes has gained significant interest
due to their biological activities and catalytic applications [8-11]. The transition metal
complexes having oxygen and nitrogen donor Schiff bases possess unusual configuration,
structural liability and are potentially sensitive to the molecular environment. Transition
metal Schiff base complexes have been widely investigated in the scientific literature [12-
17]. Medicinal inorganic chemistry has been of great attention over the past few decades.
Metal complexes have found many significant therapeutic applications such as cancer
treatment [18-20], antibacterial [21], and anti-inflammatory agents [22]. It is of great

scientific interest to mention that Schiff base complexes have gained much attention due to
their remarkable biological activities [23-25]. Copper as an essential element for human
survival and also its oxidative nature/specification has attracted the attention of inorganic
chemists to conduct their research on Cu(II) complexes with the aim of supporting the
medical applications [26-29]. The pharmaceutical activities of halogen substituted ligands
and antitumor activity of their synthesized compounds are very interesting research fields
[30]. The anti-cancer activity of some medicines like methotrexate, mercaptopurine, and
thioguanine is due to their DNA binding capability [31]. Based on these points, the DNA
binding activity for designing and developing advanced drugs is an interesting and ongoing
research field [32]. On the other hand, the bonded halogens in ligands show some advantages
like increasing in binding affinity, membrane permeability, and also enhancement in the oral
absorption [33]. For example, the effect of halide substituents on biological activities
especially the essential role of a halogen atom in drugs has been discussed [34, 35].
However, to the best of our knowledge, there is no report on the synthetic procedure of the
as-studied compounds. Therefore, the need of more and more research in this field prompted
us to investigate the DNA-binding capacity of the as-synthesized compounds. In continuation
of our previous research [36–40], we synthesized four N,O- bidentate Schiff base ligands and
also their related Zn and Cu complexes (Scheme 1). The synthesis of these ligands was
1
comprehensively investigated by IR, UV-Vis and H NMR spectroscopies. In addition,
crystalline structures of three complexes including Zn(L1)2; (Z1), [Cu(L3)2]; (C3) and
[Cu(L4)2]; (C4) were studied in detail by X-ray crystallography. Additionally, based on
crystallographic data, the DFT and TF-DFT calculations of these complexes were performed
using the B3LYP levels with Def2-TZVP basis set and then compared with the experimental
data. Finally, the docking simulation was carried out using the AutoDock Vina program and

confirmed an excellent/great correlation and relationship between estimated and experimental
data.
H
e
d
O
H
H
i
X
NH2
H
c
EtOH
HO
Br
N
H
X
R.T., 5h
HLn
HL1
X
F
HO
Br
H
H
e'
p
d'
HL2
HL3
HL4
Cl
Br
I
H
H
a
b
Br
O
N
N
X
Br
I
Cl
C2
Z2
F
M
X
X
O
M=Cu C1
M=Zn Z1
C3 C4
Z3 Z4
Cu2+
Zn2+
M
or
Br
Scheme 1. Syntheses of HL1–HL4 ligands, Z1–Z4 and C1–C4 complexes.
2. Experimental
2.1. Chemicals and physical measurements
All materials were purchased commercially from Merck and used without purification. IR
spectra were recorded on a FT-IR Prestige 21 spectrophotometer from 400-4000 cm-1 using
1
KBr pellets. H NMR spectra of the ligands and zinc complexes were recorded at ambient
temperature with a BRUKER AVANCE 400 MHz spectrometer. Elemental CHN analyses
were performed using a Heraeus CHN-O-FLASH EA 1112 elemental analyzer. The

electronic absorption spectra in the UV-Vis region were recorded by a UV-1601PC
instrument in DMSO. X-ray data of the complexes is collected on Bruker KAPPA APEX-II
CCD and STOE IPDS-II diffractometers.
2.2. Syntheses of ligands (HLn) (n=1–4)
The bidentate Schiff base ligands, HLn, were prepared by the condensation of the 2-hydroxy-
5-bromobenzaldehyde and the respective aniline (4-fluoroaniline = HL1, 4-chloroaniline =
HL2, 4-bromoaniline = HL3 and 4-iodoaniline = HL4) in a 1:1 ratio in ethanol and the
mixture was stirred for 5 h at room temperature. The resulting yellow compounds were
filtered, washed with cold ethanol and dried over fused CaCl2 overnight. The elemental
1
analysis, H NMR and IR data, clearly confirmed their composition. The syntheses of the
ligands is illustrated in Scheme 1.
HL1; 4-Bromo-2-[(4-fluorophenylimino)methyl]phenol, IR (KBr, cm-1): ν (C=N) 1618, ν (C-
1
O) 1274. UV-Vis (DMSO) λmax(nm): 224, 394. H NMR (CDCl3, 400 MHz, 298 K) δ/ppm:
13.15 (s, Hp, O-H), 8.55 (s, Hi), 7.53 (d, 4J = 2.4 Hz, Hc), 7.48 (dd, 3J = 8.8 Hz, 4J = 2.4 Hz,
3
Hb), 7.27-7.32 (m, Hd,d′), 7.12-7.18 (m, He,e′), 6.95 (d, J = 8.8 Hz, Ha). Yield, 0.270 g
(90.6%). Yield: 0.269 g (91.5 %). Elemental Anal Calc (%) for [C13H9BrFNO]: C 53.09, H
3.08, N 4.76; found: C 52.97, H 3.15, N 4.87.
HL2; 4-Bromo-2-[(4-chlorophenylimino)methyl]phenol, IR (KBr, cm-1): ν (C=N) 1612, ν (C-
1
O) 1274. UV-Vis (DMSO) λmax(nm): 229, 325, 431. H NMR (CDCl3, 400 MHz, 298 K)
δ/ppm: 13.06 (s, Hp, O-H), 8.55 (s, Hi), 7.53 (d, 4J = 2.4 Hz, Hc), 7.48 (dd, 3J = 8.8 Hz, 4J =
2.4 Hz, Hb), 7.42 (dt, 3J = 8.8 Hz, 4J = 2.4 Hz, He,e′), 7.24 (dt, 3J = 8.8 Hz, 4J = 2.4 Hz, Hd,d′),
3
6.95 (d, J = 8.8 Hz, Ha). Yield: 0.289 g (93.1 %). Elemental Anal Calc (%) for
[C13H9BrClNO]: C 50.28, H 2.92, N 4.51; found: C 50.07, H 3.02, N 4.66.

HL3; 4-Bromo-2-[(4-bromophenylimino)methyl]phenol, IR (KBr, cm-1): ν (C=N) 1612, ν (C-
1
O) 1274. UV-Vis (DMSO) λmax(nm): 226, 290, 418. H NMR (CDCl3, 400 MHz, 298 K)
δ/ppm: 13.04 (s, Hp, O-H), 8.55 (s, Hi), 7.57 (dt, 3J = 8.8 Hz, 4J = 2.4 Hz, He,e′), 7.53 (d, 4J =
2.4 Hz, Hc), 7.48 (dd, 3J = 8.8 Hz, 4J = 2.4 Hz, Hb), 7.17 (dt, 3J = 8.8 Hz, 4J = 2.4 Hz, Hd,d′),
3
6.95 (d, J = 8.8 Hz, Ha). Yield: 0.323 g (91.0 %). Elemental Anal Calc (%) for
[C13H9Br2NO]: C 43.98, H 2.56, N 3.95; found: C 43.87, H 2.69, N 4.04.
HL4; 4-Bromo-2-[(4-iodophenylimino)methyl]phenol, IR (KBr, cm-1): ν (C=N) 1612, ν (C-
1
O) 1274. UV-Vis (DMSO) λmax(nm): 237, 370. H NMR (CDCl3, 400 MHz, 298 K) δ/ppm:
13.03 (s, Hp, O-H), 8.55 (s, Hi), 7.78 (d, br, 3J = 8.8 Hz, He,e′), 7.53 (d, 4J = 2.4 Hz, Hc), 7.48
3
4
3
3
(dd, J = 8.8 Hz, J = 2.4 Hz, Hb), 7.05 (d, br, J = 8.8 Hz, Hd,d′), 6.95 (d, J = 8.8 Hz, Ha).
Yield: 0.372 g (92.6 %). Elemental Anal Calc (%) for [C13H9BrINO]: C 38.84, H 2.26, N
3.48; found: C 38.66, H 2.37, N 3.61.
2.3. Syntheses of the zinc(II) complexes
In order to synthesize the zinc(II) complexes [Zn(Ln)2] (1–4), the metal precursor Zn(OAc)2.
2H2O (0.220 g, 1 mmol) was added to a hot solution of the corresponding ligand HLn (2.0
mmol) in methanol (30 mL), the mixture was refluxed for 12 h and the resultant solution was
filtered, washed thoroughly with methanol and dried. Bright yellow crystals of Z1 suitable
for X-ray measurements were obtained from DMF solution. However, the X-ray quality
crystals for the rest of the compounds (Z2, Z3 and Z4) could not be isolated. The synthesis of
the complexes is illustrated in Scheme 1.
Note: Ln=L1–L4 are the four bidentate Schiff base ligands (HLn)
Z1; [Zn(L1)2], IR (KBr, cm-1): ν (C=N) 1606, ν (C-O) 1379. UV-Vis (DMSO) λmax(nm): 228,
274, 348, 397. 1H NMR (CDCl3, 400 MHz, 298 K) δ/ppm: 8.24 (s, Hi), 7.45 (dd, 3J = 9.2 Hz,
4J = 2.8 Hz, Hb), 7.33 (d, 4J = 2.8 Hz, Hc), 6.98-7.00 (m, Hd,d′, He,e′), 6.86 (d, 3J = 9.2 Hz, Ha).

Yield: 0.449 g (69.0 %). Elemental Anal Calc (%) for [C26H16Br2F2N2O2Zn]: C 47.93, H
2.48, N 4.30; found: C 47.78, H 2.56, N 4.51.
Z2; [Zn(L2)2], IR (KBr, cm-1): ν (C=N) 1602, ν (C-O) 1390. UV-Vis (DMSO) λmax(nm): 225,
1
3
262 ,290, 339, 408. H NMR (CDCl3, 400 MHz, 298 K) δ/ppm: 8.24 (s, Hi), 7.45 (dd, J =
4
4
3
4
9.2 Hz, J = 2.8 Hz, Hb), 7.33 (d, J = 2.8 Hz, Hc), 7.27 (dt, J = 8.8 Hz, J = 2.8 Hz, He,e′),
3
4
3
6.98 (dt, J = 8.8 Hz, J = 2.8 Hz, Hd,d′), 6.86 (d, J = 9.2 Hz, Ha). Yield: 0.489 g (71.5 %).
Elemental Anal Calc (%) for [C26H16Br2Cl2N2O2Zn]: C 45.62, H 2.36, N 4.09; found: C
45.51, H 2.43, N 4.21.
Z3; [Zn(L3)2], IR (KBr, cm-1): ν (C=N) 1602, ν (C-O) 1388. UV-Vis (DMSO) λmax(nm): 228,
286, 340, 389. 1H NMR (CDCl3, 400 MHz, 298 K) δ/ppm: 8.24 (s, Hi), 7.45 (dd, 3J = 9.2 Hz,
4J = 2.8 Hz, Hb), 7.42 (dt, 3J = 8.8 Hz, 4J = 2.8 Hz, He,e′), 7.33 (d, 4J = 2.8 Hz, Hc), 6.92 (dt, 3J
4
3
= 8.8 Hz, J = 2.8 Hz, Hd,d′), 6.86 (d, J = 9.2 Hz, Ha). Yield: 0.523 g (67.7 %). Elemental
Anal Calc (%) for [C26H16Br4N2O2Zn]: C 40.38, H 2.09, N 3.62; found: C 40.19, H 2.17, N
3.71.
Z4; [Zn(L4)2], IR (KBr, cm-1): ν (C=N) 1597, ν (C-O) 1388. UV-Vis (DMSO) λmax(nm): 230,
260, 283, 376. 1H NMR (CDCl3, 400 MHz, 298 K) δ/ppm: 8.24 (s, Hi), 7.62 (dt, 3J = 8.8 Hz,
4J = 2.8 Hz, He,e′), 7.45 (dd, 3J = 9.2 Hz, 4J = 2.8 Hz, Hb), 7.33 (d, 4J = 2.8 Hz, Hc), 6.86 (d, 3J
3
4
= 9.2 Hz, Ha), 6.80 (dt, J = 8.8 Hz, J = 2.8 Hz, Hd,d′). Yield: 0.597 g (68.9 %). Elemental
Anal Calc (%) for [C26H16Br2I2N2O2Zn]: C 36.00, H 1.86, N 3.23; found: C 35.87, H 1.97, N
3.41.
2.4. Syntheses of the copper(II) complexes
The copper complexes were synthesized by a procedure similar to that for the zinc
complexes, but using Cu(OAc)2.H2O (0.200 g, 1 mmol) instead of Zn(OAc)2.2H2O. The
brown and black single crystals of Cu(II) complexes C3 and C4 were formed after about 5

days by slow diffusion of methanol into a concentrated DMF solution of the complex at room
temperature. However, the X-ray quality crystals for the rest of the compounds (C1 and C2)
could not be isolated. The synthesis of the complexes is illustrated in Scheme 1.
C1; [Cu(L1)2], IR (KBr, cm-1): ν (C=N) 1606, ν (C-O) 1377. UV-Vis (DMSO) λmax(nm): 227,
268, 338, 440. Yield: 0.491 g (75.6 %). Elemental Anal Calc (%) for [C26H16Br2F2N2O2Cu]:
C 48.06, H 2.48, N 4.31; found: C 47.88, H 2.55, N 4.49.
C2; [Cu(L2)2], IR (KBr, cm-1): ν (C=N) 1602, ν (C-O) 1377. UV-Vis (DMSO) λmax(nm): 228,
362, 434. Yield: 0.521 g (76.3 %). Elemental Anal Calc (%) for [C26H16Br2Cl2N2O2Cu]: C
45.74, H 2.36, N 4.10; found: C 45.57, H 2.41, N 4.29.
C3; [Cu(L3)2], IR (KBr, cm-1): ν (C=N) 1604, ν (C-O) 1369. UV-Vis (DMSO) λmax(nm): 231,
275, 333, 442. Yield: 0.570 g (73.9 %). Elemental Anal Calc (%) for [C26H16Br4N2O2Cu]: C
40.47, H 2.09, N 3.63; found: C 40.38, H 2.18, N 3.74.
C4; [Cu(L4)2], IR (KBr, cm-1): ν (C=N) 1602, ν (C-O) 1369. UV-Vis (DMSO) λmax(nm): 228,
276, 341, 437. Yield: 0.619 g (71.5 %). Elemental Anal Calc (%) for [C26H16Br2I2N2O2Cu]: C
36.08, H 1.86, N 3.24; found: C 35.87, H 1.97, N 3.38.
2.5. Computational methods
All calculations were performed using Gaussian 09 set of programs [41]. Geometries of Z1,
C3 and C4 complexes in the gas phase were fully optimized at B3LYP level of theory [42].
The Def2-TZVP [43] basis set was employed for all atoms. The vibrational frequency
analyses results were obtained at the same level of theory. Vibrational frequency analyses are
without any imaginary frequency. Electronic properties of three of the complexes were
obtained in the solution phase. The natural bonding orbitals (NBO) calculations were
performed using NBO 6.0 program [44] at the B3LYP/Def2-TZVP level of theory.

2.6. X-ray crystallographic data collection and structure determination of Z1, C3 and C4
complexes
The X-ray diffraction data of Z1 is collected on STOE IPDS-II diffractometer whereas
Bruker Kappa APEXII CCD diffractometer is employed for data collection of C3 and C4.
Both diffractometers have graphite-monochromated Mo-Kα radiation. The single crystals of
complexes Z1, C3 and C4 suitable for X-ray analysis are obtained from DMF solution and
mounted on a glass fiber for data collection, respectively. X-ray data is integrated on X-
AREA [45], SADABS software [46] for zinc and copper complexes, respectively. The
structures are solved on SHELXS-97 [47] by direct methods and subsequent difference
fourier maps and then refined on F2 by a full-matrix least-squares procedure using anisotropic
displacement parameters. All non-hydrogen atoms were refined as anisotropic whereas the H-
atoms are refined as riding atoms with relative isotropic displacement parameters.
Refinement of Z1 data is performed using the X-STEP32 [48], whereas SHELXL-2018/3
[49] and WinGX-2014 [50] are utilized for refinement of C3 and C4. The crystallographic
illustrations for complexes Z1, C3 and C4 were prepared using ORTEP-3 [51], platon [52]
and Mercury 4.0 software [53]. Experimental parameters pertaining to single-crystal X-ray
analysis of complexes are given in Table 1.
Table 1. Experimental details of Z1, C3 and C4
Crystal data
CCDC
Z1
C3
C4
1974700
1962982
1962973
Chemical formula
Mr
C26H0Br2F2N2O2Zn
635.47
C26H16Br4CuN2O2
771.59
C13H8BrCu0.50INO
432.78
Crystal system, space
group
Monoclinic, P21/n
Monoclinic, P21/c
Monoclinic, P21/c
Temperature (K)
293
296
296
a, b, c (Å)
9.0495 (18), 15.182
(3), 17.792 (4)
90, 94.19 (3), 90
9.9324 (7), 10.6607
(7), 12.1891 (8)
90, 101.714 (3), 90
13.7401 (14), 8.0325
(9), 11.4914 (11)
90, 92.235 (5), 90
, ,  (°)
V (Å3)
Z
2438.0 (8)
4
1263.78 (15)
2
1267.3 (2)
4

Density (calculated)
F(000)
1.731
3
3
2.028 Mg/m
742
2.268 Mg/m
814
1216
Radiation type
Wavelength (λ)
µ (mm-1)
Mo Kα
Mo K
0.71073 Å
7.215
Mo K
0.71073 Å
6.479
0.71073 Å
4.326
Crystal size (mm)
Data Collection
Diffractometer
0.35 × 0.29 × 0.27
0.32 × 0.24 × 0.22
0.32 × 0.28 × 0.25
STOE IPDS-II diffractometer Bruker KAPPA APEXII CCD Bruker KAPPA
diffractometer
APEXII CCD
diffractometer
Absorption correction
x-scan(X-AREA; Stoe)
6563, 6563, 2176
multi-scan (SADABS; Bruker, multi-scan (SADABS;
2007)
Bruker, 2007)
No. of measured,
independent
And observed [I> 2s(I)]
reflections
10000, 2634, 1669
10840, 3002, 2067
Rint
0.690
0.039
0.052
Theta range for data
collection
2.456° to 29.362°
2.094° to 26.499°
1.483° to 27.909°
Index ranges
-12 h 12, 0 k 20, 0  l
-12 h 12, -13 k 10, -15 -18 h 18, -10 k 9,
24
0.690
l  15
0.628
-14  l 12
0.659
(sin θ/λ)max (Å-1)
Refinement
R[F2> 2σ(F2)], wR(F2), S 0.050, 0.124, 0.68
0.040, 0.093, 1.02
2634
0.041, 0.113, 1.02
3002
No. of reflections
No. of parameters
H-atom treatment
6563
316
160
161
H-atom parameters
constrained
H-atom parameters
constrained
0.51, −0.44
H-atom parameters
constrained
0.98, −1.19
Δρmax, Δρmin (e Å−3)
0.70, −1.18
2.6.1. Crystal structures of Z1, C3 and C4 complexes
In the yellow coloured single crystal Z1 (Fig. 4, Table 1), coordination sphere around the
central Zn-atom consists of two N-atoms and two O-atoms with both ligands chelating the
central Zn-atom. The chelating nitrogen atoms (N1/N2) are the distance of 2.018 (4) and
2.007 (4) Å, respectively from central Zn-atom whereas the chelating oxygen atoms (O1/O2)
are at the distance of 1.902 (3) and 1.911 (3) Å, respectively from central Zn-atom. The bond
angles in the coordination spheres ranges from 95.40 (2)° to 114.24 (2)°, thus form a
distorted tetrahedral geometry. In the first chelating ligand, the (Z)-3-iminoprop-1-en-1-ol
group A (C7/C11/C14/N1/O1), bromobenzene group B (C5/C11/C14/C16/C20/C22/Br2) and
fluorobenzene moiety C (C8/C12/C13/C17/C19/C24/F2) are planar with r. m. s deviation of

0.0101, 0.0215 and 0.0081 Å, respectively. The dihedral angle between A/B, A/C and B/C
are 1.64 (2)°, 38.3 (2)° and 36.6 (1)° respectively. This dihedral angle shows that group A
and B are almost parallel. In the second ligand, the (Z)-3-iminoprop-1-en-1-ol group D
(C2/C8/C10/N2/O2) ), bromobenzene moiety E (C1-C4/C10/C14/Br1) and fluorobenzene
moiety F (C6/C9/C21/C23/C26/C27/F1) are planar with r.m.s deviation of 0.0462, 0.0250
and 0.0083 Å, respectively. The dihedral angle between D/E, D/F and E/F are 4.7 (3)°, 62.7
(2)° and 67.2 (2)°, respectively showing that group D and E are almost parallel. The
molecules are connected with each other in the form of infinite 1D chain along
crystallographic direction [0 1 0] through C-H…O bonding as shown in Fig. 1 and given in
Table 2, where CH is from fluorobenzene moiety F and O-atom is from the (Z)-3-iminoprop-
1-en-1-ol group D. In addition of intermolecular H-bonding, weak interactions of type C-
Br…π and C-F…π interaction that helps in further strengthening of molecules as shown in Fig.
2 and given in Table 2.

Fig. 1. Packing diagram of Z1 showing formation of 1D chain along [0 1 0] by molecules with H-atoms not
engage in H-bonding are not displayed for clarity.
Fig. 2. Graphical representation of C-Br…π and C-F…π interactions for Z1

Table 2. Hydrogen-bond geometry, C-Br…π, C-F1…π interactions (Å, º) for Z1
D—H···A
D—H
0.93
0.93
0.93
0.93
H···A
3.11
2.57
2.47
2.97
D···A
D—H···A
119
160
151
136
C18—H18···Br2i
C20—H20···F2ii
C21—H21···O2iii
C24—H24···Br2iv
C—Br···π
3.658 (5)
3.461 (7)
3.313 (7)
3.698 (5)
C··· π
C—Br
Br··· π
C—Br··· π
C15—Br1···Cg(1)i
1.909
3.682(2)
4.405(7)
99.02(19)
C22—Br2···Cg(5)iii
1.920
C—F
1.379
3.907(3)
F··· π
5.519(6)
C··· π
140.2(2)
C—F··· π
98.0(3)
C—F···π
C26—F1···Cg(6)v
3.717(4)
4.141(6)
Symmetry codes: (i) x+1/2, −y+1/2, z+1/2; (ii) −x, −y, −z; (iii) −x+1/2, y−1/2, −z+1/2; (iv) x−1/2, −y+1/2, z+1/2,
(v) 1+x, y, z, where Cg(1), Cg(5) and Cg(6) are centroid of (C7/C11/C14/N1/O1/Zn1),
(C6/C9/C21/C23/C25/C26) and (C8/C12/C13/C17/C19/C24) rings, respectively.
In the brown coloured single crystal of C3 (Fig. 4, Table 1), the asymmetric unit consist of
half of the molecule (C1-C13/N1/O1/Br1/Br2) with Copper atom at the center of inversion
.The other half of the molecule (C1i-C13i/N1i/O1i/Br1i/Br2i) is symmetrically generated with
symmetry code - x, 1- y, 1- z. The coordination sphere around the central Cu-atom consists
of two N-atoms and two O-atoms. The chelating N-atom and O-atom are at the distance of
2.009(3) and 1.883 (2) Å, respectively from central Cu-atom. The bond angles N1-Cu1-O1,
N1i-Cu1-O1, N1i-Cu1-O1i and N1-Cu1-O1i in the coordination sphere are 91.05 (14)°, 88.98
(14)°, 91.05 (14)° and 88.92 (14)°, thus forming a slightly distorted square planar geometry.
In the half molecule of C3 (C1-C13/N1/O1/Br1/Br2), the (Z)-3-iminoprop-1-en-1-ol moiety
A (C1/C6/C7/N1/O1), first bromobenzene moiety B (C1-C6/Br1) and the second
bromobenzene moiety C (C8-C13/Br2) are planar with r.m.s deviation of 0.0315, 0.0085,
0.0146 Å, respectively. The dihedral angles between A/B, A/C and B/C are 1.13 (2)°, 54.71
(1)° and 54.65 (1)°, respectively showing that the moieties A and are almost parallel to each

other. No intra or intermolecular H-bonding is found. The molecules are connected with each
other through weak non-covalent interaction of type C-H…π as shown in Fig. 3.
Fig. 3. Graphical presentation of weak C-H…π interaction for C3 with distances shown are in Å.
In the black coloured single crystal of C4 (Fig 4, Table 1), the asymmetric unit consist of half
of the molecule (C1-C13/N1/O1/Br1/I1) with Copper atom at the center of inversion. The
other half of the molecule (C1i-C13i/N1i/O1i/Br1i/I1i)) is symmetrically generated with
symmetry code 1- x, 1- y, - z. The coordination sphere around the central Cu-atom consists
of two N-atoms and two O-atoms. The chelating N-atom and O-atom are at the distance of
2.017 (4) and 1.880 (4) Å, respectively from central Cu-atom. The bond angles N1-Cu1-O1,
N1i-Cu1-O1, N1i-Cu1-O1i and N1-Cu1-O1i are 90.93 (16)°, 89.07 (16)°, 90.93 (16)° and

89.09 (16)°, thus forming a slightly distorted square planar geometry. In the asymmetric unit,
the (Z)-3-iminoprop-1-en-1-ol moiety A (C1/C6/C7/N1/O1), bromobenzene moiety B (C1-
C6/Br1) and the iodobenzene moiety C (C8-C13/I1) are planar with r.m.s deviation of
0.0476, 0.0053, 0.0197 Å, respectively. The dihedral angles between A/B, A/C and B/C are
2.21 (7)°, 40.03 (1)° and 39.2 (1)°, respectively showing that moieties A and B are almost
parallel to each other. No intra or intermolecular H-bonding is found.
Z1

C3
C4
Fig. 4. The ORTEP of Z1, C3 and C4 complexes with thermal ellipsoids plotted at the 50% probability level.
Hydrogen atoms are shown by small circles of arbitarary radii.
2.7. DNA binding studies
2.7.1. UV–Vis absorption titrations
Interaction of the synthesized compounds with FS-DNA (Fish Sperm-DNA) was investigated
using absorption spectroscopy in 50 mM Tris-HCl buffer at pH 7.5, in order to investigate the
possible binding modes to FS-DNA and to calculate the binding constants (Kb). Stock
solutions of all the synthesized compounds were freshly prepared by dissolving them in
DMSO and then diluting suitably with Tris-HCl buffer to required concentrations. The used
reference solutions were solution of Tris-HCl with 3% DMSO by volume. Interaction of the
ligands and complexes with FS-DNA was studied using absorption spectroscopy. For FS-
DNA, stock solutions were prepared in Tris-HCl buffer which after adequate dilution with the
buffer, its concentration per nucleotide was determined by UV spectrophotometry using 6600
M−1 cm−1 as the molar absorption coefficient at 260 nm. FS-DNA had a ratio of UV

absorbance at 260 and 280 nm of 1.9:1 (A260/A280=1.9), indicating that DNA was sufficiently
free of protein [54]. The absorption titration experiments were performed by keeping constant
the compounds concentration (80 µM), while gradually increasing the concentration of the
FS-DNA. Absorption spectra were recorded after equilibrium at 20°C for 2 min. While
measuring the absorption spectra, equal amounts of DNA was added to both compounds and
references to eliminate the absorbance of DNA, therefore Tris buffer was subtracted through
base line correction.
2.7.2. Molecular docking studies
In this study, molecular docking calculations were performed to simulate the interaction of
the compounds with DNA, using the AutoDock Vina software [55]. The crystal structure of
duplex DNA (PDB ID: 423D) with sequence d(ACCGACGTCGGT)2 was downloaded from
Brookhaven Protein Data Bank (http://www.rcsb.org/pdb) at resolution of 1.60 Å. The 3D
structures of the ligands and complexes was generated using the CIF files of their X-ray
crystal structures. The CIF files were converted to the PDB format by using the Mercury
software (http://www.ccdc.cam.ac.uk/). Water molecules of the pdb files were removed,
missing hydrogen atoms and Gasteiger charges were added. Flexible-ligand docking was
performed by AutoDock 4.2 molecular-docking program using the implemented empirical
free energy function and the Lamarckian Genetic Algorithm [56]. The Gasteiger charges
were added to prepare the macromolecule input files for docking and the Auto Grid was used
to calculate Grids. To study the interaction of the synthesized compounds and DNA model, a
blind docking with 126 lattice points along X, Y, and Z axes was performed to find the active
site of ligands to the biomacromolecules. The dimensions of the grid map were selected 60
points with a grid point spacing of 0.375 Å, after determination of the active site. For each
run, 200 docking runs with 25,000,000 energy evaluations were used.

3. Results and discussion
3.1. Syntheses
Condensation of 2-hydroxy-5-bromobenzaldehyde with equimolar amounts of the respective
aniline leads to the formation of an important class of the bidentate Schiff base ligands. The
Schiff base ligands HL1, HL2, HL3 and HL4 were prepared by the reaction of 2-hydroxy-5-
bromobenzaldehyde with the corresponding 4-flouroaniline, 4-chloroaniline, 4-bromoaniline
and 4-iodoaniline in nearly 80–90% yield in ethanol. These Schiff base ligands are the stable
solids and can be stored without precautions. Treatment of the Schiff base ligands HL1–4 with
the respective metal salt, Zn(OAc)2.2H2O and Cu(OAc)2.H2O, in a 2:1 M ratio under reflux
condition led to the zinc(II) complexes (Z1–Z4) and copper(II) complexes (C1–C4). Crystals
of complexes Z1, C3 and C4 suitable for X-ray diffraction could be isolated from DMF after
slow evaporation of the solvent over a period of two week. The spectroscopic data is in good
agreement with the chemical formula proposed for Schiff base complexes. The synthetic
procedure of Schiff base ligands and their complexes presented in Scheme 1.
3.2. lH NMR Spectra
1H NMR spectra of the compounds were recorded in deuterated chloroform (CDCl3). The
results are given in Table 2 and the spectra of the compounds are shown in Figs. S1-S16. In
the 1H NMR spectra of the HL1-4 (Figs. S1, S5, S9 and S13), signals at  = 13.15,  = 13.06, 
= 13.04 and  = 13.03 ppm which corresponded to the phenolic OH resonances are
disappeared in the spectra of the Zn complexes (Figs. S3, S7, S11 and S15). These clearly
indicates that the Schiff base ligands are coordinated as an anionic ligands to the Zn(II) ions.
In the 1H NMR spectra of the Zn complexes, the signals at  = 8.24 ppm are attributed to the
Hi-C=N- proton of imine. There are slight shifts of the imine protons to lower field in the

1
obtained H NMR spectra of the complexes compared to the ligands. This shift confirms the
coordination of the phenolic oxygen and imine nitrogen to metal ions.
1
In H NMR spectra of the compounds, the absorption peaks of aromatic ring protons are
between 6 and 8 ppm (Figs. S1-S16). The Ha proton is coupled to the Hb proton and shows
doublet peaks at 6.95 ppm [3J(a,b) = 8.8 Hz]. The Hb proton coupled to Ha shows doublet and
gives another doublet by coupling Hc as being 7.48 ppm [3J(a,b) = 8.8 Hz, 4J(b,c) = 2.4 Hz]. The
Hc proton is coupled to the Hb proton and shows doublet at 7.53 ppm [4J(b,c) = 2.4 Hz]. The Hd
proton coupled to He shows doublet and gives triplet by coupling Hd′ and He′ [3J = 8.8 Hz, 4J
= 2.4 Hz]. The He proton coupled to Hd shows doublet and gives triplet by coupling He′ and
Hd′ [3J = 8.8 Hz, 4J = 2.4 Hz]. These results are in accordance with the literature values [57].
Table 2. Characteristic 1H NMR chemical shift values (ppm), peak multiplicity and coupling constant J (Hz) for
the synthesised compounds recorded in CDCl3
compound
Ha
Hb
7.48 dd
J = 8.8; 2.4
7.45 dd
J = 9.2; 2.8
7.48 dd
J = 8.8; 2.4
7.45 dd
J = 9.2; 2.8
7.48 dd
J = 8.8; 2.4
7.45 dd
J = 9.2; 2.8
7.48 dd
Hc
Hd, Hd′
7.27-7.32 m
He, He′
7.12-7.18 m
Hi
8.55 s
Hp
13.15 s
HL1
6.95 d
J = 8.8
6.86 d
J = 9.2
6.95 d
J = 8.8
6.86 d
J = 9.2
6.95 d
J = 8.8
6.86 d
J = 9.2
6.95 d
J = 8.8
6.86 d
J = 9.2
7.53 d
J = 2.4
7.33 d
J = 2.8
7.53 d
J = 2.4
7.33 d
J = 2.8
7.53 d
J = 2.4
7.33 d
J = 2.8
7.53 d
J = 2.4
7.33 d
J = 2.8
Z1
HL2
Z2
6.98-7.00 m
6.98-7.00 m
8.24 s
8.55 s
8.24 s
8.55 s
8.24 s
8.55 s
8.24 s

13.06 s

7.24 dt
J = 8.8; 2.4
6.98 dt
J = 8.8; 2.8
7.17 dt
J = 8.8; 2.4
6.92 dt
J = 8.8; 2.8
7.05 d, br
J = 8.8
7.42 dt
J = 8.8; 2.4
7.27 dt
J = 8.8; 2.8
7.57 dt
J = 8.8; 2.4
7.42 dt
J = 8.8; 2.8
7.78 d, br
J = 8.8
HL3
Z3
13.04 s

HL4
Z4
13.03 s

J = 8.8; 2.4
7.45 dd
J = 9.2; 2.8
6.80 dt
J = 8.8; 2.8
7.62 dt
J = 8.8; 2.8
3.3. Optimized Structures
Optimized geometries of complexes Z1, C3 and C4 are shown in Fig. 3. Selected calculated
bond lengths and angles along with the experimentally determined data for Z1, C3 and C4
are listed in Table 3. The calculated bond lengths and angles at B3LYP/Def2-TZVP level of
theory in the gas phase are in agreement with the corresponding experimental values. There

are some differences between theoretical and experimental values because the DFT
calculations were donein the gas phase without any scaling, but experimental values obtained
in the solid phase [58]. Therefore, it is probable that the difference in the bond lengths and
angles in complexes is a result of negligible inter or intramolecular interactions in DFT
calculations. In agreement with X-ray crystal structures, the coordination around the metallic
center of Z1, C3 and C4 in the gas phase through the nitrogen and oxygen atoms exhibit the
distorted tetrahedral, square planar and square planar geometries, respectively (Figs. 1, 3).
C3
C4
Z1
Fig 3. Optimized structures of Z1, C3, and C4 complexes at B3LYP/Def2-TZVP level of theory.

Table 3. Some selected bond lengths (A°) and bond angles (°) of complexes Z1, C3, and C4.
Z1 C3
C4
Exp
Calc
Exp
Calc
Exp
Calc
Bond lengths
M1–O1
M1–O2(1i)
M1–N1
M1–N2(1i)
1.899(4)
1.907(4)
2.014(4)
2.011(4)
1.956
1.956
2.048
2.048
1.883(3)
1.883(3)
2.010(3)
2.010(3)
1.923
1.923
2.016
2.016
1.899(4)
1.907(4)
2.014(4)
2.011(4)
1.923
1.923
2.017
2.017
Bond angles
O1–M1–N1
O2(1i)–M1–N2(1i)
N1–M1–N2(1i)
O1–M1–O2(1i)
O1–M1–N2(1i)
N1–M1–O2(1i)
96.33(17)
95.27(16)
102.34(17)
114.38(18)
124.70(19)
125.96(18)
95.65
95.65
119.08
115.23
116.40
116.40
91.05(13)
88.95(13)
180.0
180.0
88.95(13)
88.95(13)
93.02
93.04
155.67
149.83
93.26
93.24
90.93(16)
90.93(16)
180. 0
180.0
89.07(16)
89.06(16)
93.05
93.05
155.45
150.05
93.25
93.25
3.4. IR Spectral Studies
The IR spectra of ligands and complexes were shown in the supplementary information. In
the IR spectra of the free ligands, the azomethene (-C=N) bands are observed at 16012-1618
cm-1; these bands shift to 1606-1602 cm-1 upon coordination to metal. While the C–O
stretching band of the Schiff base ligands shifts from 1274 cm-1 to higher wave numbers
after complexation (1350 cm-1). This indicates that the nitrogen and oxygen atoms from the
ligand participate in the coordination to the metal ion (Figs. S17-S20). The frequency
calculation could predict all of vibrational modes without any imaginary frequencies.
Typical selected experimental and calculated vibrational modes of the Z1, C3, and C4
complexes are collected in Table 4. Theoretical calculations confirmed good agreement
between experimental and calculated results.
Table 4. Some selected experimental and calculated vibrational modes (cm-1) of the Z1, C3 and C4 complexes.
휐(M‒O)
Calc
휐(M‒N)
Calc
휐(C=N)
Calc
휐(C‒O)
Calc
complex
Z1
C3
Exp
661
650
650
Exp
495
495
495
Exp
Exp
657
660
660
517
511
510
1606
1604
1602
1625
1619
1615
1379
1369
1369
1350
1352
1352
C4
3.5. Electronic Spectral Studies
In order to calculate the electronic properties in the Z1, C3 and C4 complexes, TD-DFT calculations

were performed at the B3LYP/Def2-TZVP level of theory. The electronic absorption spectra of the
ligands and their Zn(II) and Cu(II) complexes were recorded in DMSO (Figs. S21-S24). The nature
of electronic transitions in TD-TDFT data for Z1, C3 and C4 were analyzed by NBO-CMO
calculations. The electronic spectroscopic data of the Z1, C3 and C4 complexes are listed in Table
5. Typically, the most important transition is the one with the least energy. The lowest energy
transition of Z1 in charge transfer table was calculated at 3.068 eV and attributed to
HOMO→LUMO (89%) and HOMO-1→LUMO+1 (11%). For the C3 and C4 the lowest calculated
energy are 3.106 eV and 3.049, respectively attributed to [HOMO→LUMO(22%),
HOMO→LUMO+1(36%)], and [HOMO→L(35%), HOMO→LUMO+1(41%), HOMO-2→LUMO
(10%)], respectively. The major contribution in these absorption bands has inter ligand charge-
transfer (ILCT) character. Fig. 4 shows the shape of the HOMO-1, HOMO, LUMO and LUMO+1 in
the Z1, C3 and C4 complexes.
Table 5. UV−Vis absorption data from TD-DFT calculations based on B3LYP/Def2-TZVP method for
complexes Z1, C3 and C4.
E(eV) Fos
λmax(nm)
Assignment Transition
Character
ILCT
Calc
404
Exp
397
H→L(89%)
Z1
3.068
3.097
3.244
3.869
4.314
0.310
π → π*
H-1→L+1(11%)
H-1→L(72%)
H→L+1(27%)
0.328
0.077
0.478
0.273
401
382
320
287
348
274
228
π → π*
π → π*
π → π*
H-1→L+1(89%)
H→L(11%)
H-2→L(70%)
H-3→L+1(24%)
H-4→L+1(44%)
H-5→L(29%)
ILCT
ILCT
ILCT
C3
C4
3.106
3.159
3.342
3.479
3.049
3.062
3.352
3.481
0.227
0.138
0.041
0.039
0.518
0.078
0.059
0.097
399
392
370
356
406
404
369
356
442
333
275
231
437
π → π*
π → π*
π → π*
π → π*
π → π*
H→L(22%),H→L+1(36%)
H→L+1(36%),H→L+2(36%),H-3→L(11%)
H-1→L(10%),H-1→L+1(57%),H→L+1(14%) ILCT
H-2→L+1(38%),H-1→L+1(11%)
H→L(35%),H→L+1(41%),H-2→L(10%)
H→L+1(38%),H→L+2(49%)
H-1→L+2(62%),H→L+1(13%)
H-2→L+1(25%)
ILCT
ILCT
ILCT
ILCT
π → π*
π → π*
341
276,
228
ILCT
ILCT
The assignments are evaluated by NBO analysis at the B3LYP/Def2-TZVP level of approximation.

Z1
C3
C4
LUMO+1
LUMO
HOMO
HOMO-1
Fig. 4. Shape of the orbitals HOMO-1, HOMO, LUMO and LUMO+1 for Z1, C3 and C4 complexes.
3.6. Interaction with DNA
3.6.1. UV–Vis Absorption Titrations

UV–Vis absorption spectroscopy is found to be an effective tool to examine the binding
mode of DNA with metal complexes. Hence, to explore the possibility of binding of the
synthesized complexes to FS-DNA, electronic absorption of the complexes in the absence or
the presence of DNA were measured and given in Fig. 5. The absorption spectrum of all of
the ligands and complexes showed significant hypochromic effect upon the addition of FS-
DNA and also moderate red shift was observed in some complexes, revealing strong binding
of these compounds with DNA. Such spectral changes was clearly resulted from the
intercalative mode of binding and have been attributed to π–π stacking interactions between
DNA base pairs and the π electron cloud of the interacting ligand [59, 60]. As shown in fig. 5,
the absorption spectra of the ligands HL1 and HL2 exhibited both hypochromism and
hyperchromism without shifts which led to appearance of distinctive isosbestic point at 280
nm in both titrations. These findings pointed out the equilibrium between the bound and free
ligands [61]. To quantitatively evaluate the affinity of the compounds with FS-DNA, the
intrinsic binding constant Kb was determined by monitoring the changes in absorbance using
the Benesi–Hildebrand equation (1) [62]:
[DNA]/(a-f) = [DNA]/(b-f) + 1/Kb(b-f)
(eq.1)
Where [DNA] is the concentration of FS-DNA; the absorption coefficients εa, εf, and εb
correspond to the apparent extinction coefficient, the extinction coefficient for free
compounds and the extinction coefficient for the compounds in fully bound form,
respectively. εf was determined by calibration curve and εa is the ratio of Aobs to [compound].
A plot of [DNA]/(εa -εf) versus [DNA] gives Kb as ratio of slope to y-intercept [27]. The
binding constants of FS-DNA with the synthesized compounds are given in Table 6.
Table 6. DNA-binding constant (Kb) of ligands and their metal complexes.
Compounds
HL1
Kb (M-1)
1.4 × 105
3.5 × 105
Compounds
Kb (M-1)
1.9 × 105
4.0 × 105
Compounds
Z1
Kb (M-1)
6.6 × 105
7.6 × 105
C1
HL2
C2
Z2

HL3
HL4
4.0 × 105
3.4 × 105
C3
C4
4.6 × 105
5.8 × 105
Z3
Z4
1.0 × 106
2.0 × 106
It can be seen that except for the ligands, in each column, Iodo-substituted compound has
higher binding constant than the other analogues suggesting much stronger binding. The
binding constant of HL2, HL3 and HL4 ligands are about the same, and it is independent of
the halogen atom. Generally, the order of binding efficiency is as follow:
(HL1<HL2≈HL3≈HL4), (C1<C2<C3<C4), (Z1<Z2<Z3<Z4)
TabatabaeiDakhili, et al studied FDI-6 drug, halogen containing and it is interestinge that
they concluded the 4-(halo)phenyl ring is essential for their anticancer activity. They also
declared “there was an inverse correlation between the electronegativity of the halogen atom
and the potency of the corresponding derivative, in which the lower the electronegativity of
the halogen atom, the higher the potency” that our results is in a good agreement with this
conclusion [30]. It is noteworthy to note that in each raw, the binding energy of zinc
complexes are more than copper ones and ligands.
HL1
HL2

HL3
HL4
C1
C2
C3
C4

Z1
Z2
Z3
Z4
Fig 5. The change of electronic absorption spectra of the synthesized compounds (8  10-5 M) upon addition of
various amounts of FS-DNA (4  10-4 M).
3.6.2. Molecular Docking Studies
Herein, to obtain further insight into the nature of DNA binding of the synthesized
compounds, molecular docking studies were performed. The results revealed that all the
ligands and the Zn(II) complexes binds in the minor groove of DNA, while all the Cu(II)
complexes preferred major groove (Fig. 6). The binding mode, the nucleotides around each of
the synthesized compounds and also their bonds with DNA are shown in this figure. In figure
6, the small green spheres show H-bond interaction in these compounds. As shown, all the
ligands and Cu(II) complexes formed hydrogen bond with nucleotide of DNA. The ligands
form hydrogen bonding through imine nitrogen and hydroxyl oxygen with some key residues