Synthesis, in vitro anticancer activities, and quantum chemical investigations on 1,3-bis-(2-methyl-2-propenyl)benzimidazolium chloride and its Ag(I) complex

Article abstract of DOI:10.1177/1747519820950219

1,3-Bis-(2-methyl-2-propenyl)benzimidazolium chloride and its Ag(I) complex are synthesized and the structures are elucidated using spectroscopies techniques. The molecular and crystal structures of the benzimidazolium salt are confirmed by X-ray crystallography. The molecular geometries of the benzimidazolium and its Ag(I) salt are analyzed using the B3LYP functional with the 6–311+G(d,p)/LANL2DZ basis set. The observed Fourier transform infrared and nuclear magnetic resonance isotropic shifts are compared with the calculated values. Besides, the quantum chemical identifiers, significant intramolecular interactions, and molecular electrostatic potential plots are used to show the tendency/site of the chemical reactivity behavior. The three-dimensional Hirshfeld surfaces and the associated two-dimensional fingerprint plots are applied to obtain an insight into the behavior of the interactions in the crystal. Both compounds are tested for their in vitro anticancer activities against DU-145 and MCF-7 cancer cells and L-929 non-cancer cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Full text of DOI:10.1177/1747519820950219

9
research-arti
5cle2020 0219CHL0010.1177/1747519820950219Journal of Chemical ResearchSerdaroğlu et al.
Research Paper
Journal of Chemical Research
–12
1
Synthesis, in vitro anticancer activities,
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and quantum chemical investigations on
1
,3-bis-(2-methyl-2-propenyl)benzimidazolium
chloride and its Ag(I) complex
1
2
Goncagül Serdaroğlu , Serap Şahin-Bölükbaşı ,
Duygu Barut-Celepci , Resul Sevinçek , Neslihan Şahin4,5,6,
3
3
5
,6
5,6
Nevin Gürbüz and İsmail Özdemir
Abstract
1
,3-Bis-(2-methyl-2-propenyl)benzimidazolium chloride and its Ag(I) complex are synthesized and the structures are
elucidated using spectroscopies techniques. The molecular and crystal structures of the benzimidazolium salt are
confirmed by X-ray crystallography. The molecular geometries of the benzimidazolium and its Ag(I) salt are analyzed
using the B3LYP functional with the 6–311+G(d,p)/LANL2DZ basis set. The observed Fourier transform infrared and
nuclear magnetic resonance isotropic shifts are compared with the calculated values. Besides, the quantum chemical
identifiers, significant intramolecular interactions, and molecular electrostatic potential plots are used to show the
tendency/site of the chemical reactivity behavior. The three-dimensional Hirshfeld surfaces and the associated two-
dimensional fingerprint plots are applied to obtain an insight into the behavior of the interactions in the crystal. Both
compounds are tested for their in vitro anticancer activities against DU-145 and MCF-7 cancer cells and L-929 non-
cancer cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.
Keywords
anticancer activity, crystal structure, density-functional theory studies, Hirshfeld analysis, N-heterocyclic carbene
Date received: 16 June 2020; accepted: 23 July 2020
1Department of Science Education, Faculty of Education, Sivas
Cumhuriyet University, Sivas, Turkey
Department of Biochemistry, Faculty of Pharmacy, Sivas Cumhuriyet
5Department of Chemistry, Faculty of Arts and Sciences, İnönü
University, Malatya, Turkey
Catalysis Research and Application Center, Inönü University, Malatya, Turkey
2
6
University, Sivas, Turkey
Department of Physics, Faculty of Sciences, Dokuz Eylül University,
3
Corresponding author:
İzmir, Turkey
Goncagül Serdaroğlu, Department of Science Education, Faculty of
Education, Sivas Cumhuriyet University, 58140 Sivas, Turkey.
Email: gserdaroglu@gmail.com
4
Department of Basic Education, Faculty of Education, Sivas Cumhuriyet
University, Sivas, Turkey
Creative Commons Non Commercial CC BY-NC: This article is distributed under the terms of the Creative Commons
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reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and
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2
Journal of Chemical Research 00(0)
Introduction
H
N
N-heterocyclic carbenes (NHCs) are aromatic organic com-
pounds that contain at least three carbon and two nitrogen
atoms. NHCs were first reported by Öfele, Wanzlick, and
THF
60
N
N
DMF
80
N
Cl-
+
+
NaH
+
Cl
+
Cl
o
o
N
C
C
N
1
1
,2
Schönherr. In general, NHCs are not easy to isolate as
single carbene monomers due to their decomposition in the
presence of water or their dimerization. All approaches to
obtain a stable N-heterocyclic carbene had failed, until
Scheme 1. Synthesis of NHC ligand 1.
3
Arduengo reported the first isolated NHC in 1991. Recently,
the use of N-heterocyclic carbenes in coordination chemis-
try has attracted considerable attention due to their large
steric demand and excellent electronic properties, namely,
N
N
N
+
CH
Cl
2
2
Cl-
+
Ag O
2
Ag Cl
N
Light
4–8
high σ-basicity and low π-acidity, which foster increased
excluded, r.t.
9–16
activity in catalytic systems.
Benzimidazole-based
N-heterocyclic carbenes are stable systems and are the sub-
ject of significant interest because of pharmacological activ-
ities such as antitumor, antibacterial, and antifungal.
1
2
1
7
18
19
Scheme 2. Synthesis of Ag(I)–NHC complex 2.
Most NHCs are prepared by deprotonation of azolium pre-
2
0,21
cursors with a simple metal salt or a strong base.
Also,
supramolecular assembly of such complexes. Quantum
chemical studies were conducted on two compounds to
estimate the electronic, spectroscopic, and biological reac-
tivity behavior. With this aim, the geometric structures of
the two compounds were predicted, then the assigned NMR
shifts and IR assignments of these compounds were com-
pared with the corresponding experimental values. A fron-
tier molecular orbital (FMO) investigation was applied, and
molecular electrostatic potential (MEP) diagrams were
drawn to estimate/evaluate the chemical reactive behavior/
site of two compounds. The in vitro anticancer activity of
the benzimidazolium salt 1 and the Ag(I) complex 2 was
investigated against DU-145 human prostate cancer cells,
MCF-7 human breast cancer cells, and mouse L-929 non-
cancer adipose cells from the mouse for 24, 48, and 72h
using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo-
NHCs can be obtained from imidazolidine sources.2
2
Halide anions have been the subject of increasing
research in investigations of both environmental and supra-
molecular chemistry, since halides are among the most
common anions in natural environments. Among halides,
chloride plays a vital role in all body fluids because it is
responsible for maintaining acid/base balance, transmitting
2
3,24
nerve impulses, and so on.
In addition, water is an
essential molecule in all aspects of human life, so these
water−chloride interactions are of fundamental importance
to be able to understand solution phenomena, materials
chemistry, drug design, catalysis, and atmospheric
2
5,26
research.
In recent years, monochloride hydrates
[
Cl(H O)n]– have been extensively investigated using
2
experimental and theoretical techniques, and they have
addressed issues such as stability and structure. In addition,
the Pt(0) complexes of benzimidazolylidene carbene
ligands have been developed and investigated in terms of
32
lium bromide (MTT) assay.
2
7
their ability to catalyze alkene hydrosilylation reactions.
Results and discussion
2
8
29
Recently, the catalytic activity of Pd(II) and Co(II) com-
plexes of structurally related benzimidazole-based NHCs
have been reported. In a study related to different types of
Molecular structures of the NHC ligands
and Ag(I)–NHC complexes
Ag(I)–L complexes, the antiproliferative activity of such NHC ligand 1 was obtained by binding two 2-methyl-
metal complexes against cancer cells was investigated and 2-propenyl units to benzimidazole. The synthesis reaction
the results showed that they had selectivity toward the steps are shown in Scheme 1.
3
0
human breast cancer cells.
The synthesized NHC ligand 1 and Ag O were mixed in
2
The aim of this paper is to report the preparation and dichloromethane with the exclusion of the light to give
characterization of benzimidazolium salt 1 and its Ag(I)– Ag(I)–NHC complex 2 in excellent yield. The synthetic
NHC complex 2. Characterization was performed using route is shown in Scheme 2.
1
13
H nuclear magnetic resonance (NMR), C NMR, and
The optimized parameters of the compounds were veri-
Fourier transform infrared (FTIR) spectroscopies for fiedbyfrequencycalculationsattheB3LYP/6–311+G(d,p)/
both compounds. Single-crystal X-ray diffraction was LANL2DZ are summarized in Table 1. These values were
used to elucidate the molecular and crystal structure of the then compared with the experimental values of compound
benzimidazolium salt. The X-ray results revealed that the 1 determined by X-ray crystallography. The optimized
asymmetric unit hosts a cation, a chloride anion, and a geometries and atom labeling of each compound are shown
water molecule, which are bonded to each other through an in Figure 1.
intricate hydrogen-bonding network. It was reported that
First, it should be noted that there are small differences
the chloride hydrate structures ([Cl (H O) ] –) in the crys- between the experimental and computational data because
2
2
2 2
tal structure, due to the formation of the hydrogen- the experimental results were recorded for the solid-state
3
1
bonded cluster, have caused a supermolecular structure.
structure of the molecule. From Table 1, the N11–C13 bond
Crystallographic studies are useful to investigate the length was recorded as 1.321Å and calculated (for 1 and 2)

Serdaroğlu et al.
3
Table 1. The selected geometric parameters of compounds 1
and 2.
2. However, the N11–C16–C17 and N12–C25–C26 bond
angles observed at 112.0° and 111.5° were estimated as
113.4° and 112.6° for 1 and as 114.00° for 2. Here, it should
be noted that the calculated angles deviate from the experi-
mental angle value by approximately 2°. However, the
C13–N12–C25-C26 dihedral angles for the two compounds
were calculated as −98.7° and −110.7°, being almost planar
to the ring of each compound, while this angle deviated by
Exp.a
1
2
Bond lengths (Å)
N11–C13
N11–C1
N11–C16
N12–C13
N12–C2
N12–C25
C1–C2
C2–C3
C3–C4
C4–C5
C5–C6
C6–C1
C16–C17
C17–C20
C17–C24
C25–C26
1.321(3)
1.338
1.398
1.476
1.332
1.398
1.484
1.404
1.394
1.387
1.409
1.389
1.395
1.515
1.505
1.334
1.516
1.334
1.506
1.357
1.396
1.470
1.357
1.397
1.470
4.402
1.394
1.392
1.405
1.392
1.394
1.516
1.505
1.334
1.516
1.394(3)
1.470(4)
1.325(4)
1.392(3)
1.470(3)
1.381(3)
1.386(3)
1.369(3)
1.392(3)
1.370(3)
1.386(3)
1.494(4)
1.492(4)
1.308(4)
1.498(4)
1.314(4)
1.476(4)
3
.7° and 15.7° from the observed value of −95° for 1.
Furthermore, the dihedral angles of N11–C16–C17-C20 for
compounds 1 and 2 were calculated as −55.7° and −54.4°
with a deviation of −13.9° and −15.2° from the recorded
value for 1 of −69.6°. Recently, the C3–C2–C1–N11 and
C6–C1–C2–C3 dihedral angles of a structurally related
3
4
compound were calculated as 179.0°. In this study, the
same dihedral angle was recorded as 177.4° and calculated
as 177.9° for compound 1 and as 179.1° for compound 2,
respectively. Here, it is worth mentioning that the simulated
data are in good agreement with the counterparts observed
in the experiment, even though there are some differences
C26–C33
C26–C29
1.334 between them.
1.505
Bond angles (°)
C13–N11–C16
C13–N12–C25
N11–C16–C17
N12–C25–C26
C1–N11–C16
C2–N12–C25
C16–C17–C20
C29–C26–C33
C16–C17–C24
C25–C26–C33
Torsion angles (°)
N11–C1–C2–N12
N11–C1–C2–C3
C13–N12–C2–C1
C13–N12–C2–C3
C13–N12–C25–C26
C13–N11–C1–C6
N11–C1–C6–C5
N11–C16–C17–C20
N11–C16–C17–C24
N12–C25–C26–C29
N12–C25–C26–C33
Vibrational analysis
126.0(2)
126.4(2)
112.0(2)
111.5(2)
125.9(2)
125.6(2)
123.0(3)
123.6(3)
120.5(3)
120.8(3)
125.3
124.8
124.8
114.0
114.0
124.6
124.6
116.7
123.1
120.0
120.0
125.9
113.4
112.6
126.8
126.2
116.8
123.5
119.6
119.3
The infrared spectra of the NHC 1 and Ag(I)–NHC 2 are
presented in Figures S3(a) and (b) in supplemental mate-
rial; a comparison of the experimental and the scaled theo-
retical vibrational frequencies can be found in Table S1 (see
the supplemental material).
In the literature, the stretching vibrations of the C–H
bonds have been reported in the region of 3000–
−1 35–37
3
100cm .
In this study, the vibrations of the C–H aro-
matic stretching (νCH RA) modes of 1 and 2 occurred at
−1
3
113 and 3104cm , whereas the counterparts of these
−0.4(4)
177.4(4)
0.3(2)
−177.1(2)
−95.0(3)
177.2(2)
−177.2(3)
−69.6
−0.2
177.9
0.3
−177.5
−98.7
178.5
−178.0
−55.7
127.1
61.0
0.0
179.1
0.3
−178.7
−110.7
178.6
−178.8
−54.4
128.7
modes for 1 and 2 were simulated in the range of 3113–
088cm− and at 3112cm , respectively. Besides, the
1
−1
3
ν C–H (ν C24–H2 and ν C33–H2) vibrational modes of
as
as
as
the carbene parts of 1 and 2 were assigned as 3116 and
−1
−1
3
118cm , and 3112cm as a pure mode, whereas the sym-
metric stretching modes of these groups (νC24–H2 and
−1
νC33–H2) were predicted as 3037–3028cm (1) and as
1
3
033–3032cm− (2). The symmetric stretching modes of
112.4(3)
57.7(3)
−124.8(3)
the methyl groups (νC20–H3 and νC29–H3) for the com-
55.2
−127.9
pounds were recorded as 2937cm− (1) and as 2914cm
1
−1
−121.6
−1
(
2
2), and assigned in the range of 2926cm (85%)–
916cm (87%) for 1 and as 2927cm (87%) for 2. From
aThe experimental parameters are based on the single-crystal X-ray
structure of compound 1.
−1
−1
−
1
Table S1, the appearing peaks for 1 at 3052 and 3032 cm
were assigned as the νC24–H2 and νC33–H2 modes calcu-
as 1.338 and 1.357Å. The N11–C16 single bond lengths lated at 3037cm− (98%) and 3028 cm (99%).
1
−1
characterized by single bonding for 1 and 2 were computed
The aromatic ring C–C stretching (νCC RA) mode for 1
as 1.476 and 1.470Å, with the corresponding experimental was assigned as 1682cm− (63%) and 1053 cm (72%) as
1
−1
bond length being 1.47Å. In the literature, the C–N bond a pure mode, while this mode has a contribution to the
−
1
length and N–C–N bond angle for benzimidazolium chlo- bending modes in the spectral region of 1671–427 cm .
3
3
ride hydrate have been observed at 1.4Å and 111.1° and For example, the observed peaks for 1 at 1552, 1186, and
−1
calculated for the structurally related benzimidazolium 800cm were assigned by potential energy distribution
chloride at 1.4Å and 110.8° at the B3LYP/6–311++G(d,p) (PED) analysis at 1549, 1176, and 801cm− as combined
1
3
4
level of theory. Furthermore, the C13–N11–C16 bond modes with ipb (in-plane bending) HCC RA. However, the
−1
angles for 1 and 2 are calculated as 125.3° and 124.8°, νCC RA mode for 2 was assigned at 1676cm (59%) and
which are ~1° different from the observed angle of 126.0°. 1057cm− (56%) as a pure mode, calculated at 1672, 1541,
1
−1
Similarly, the C13–N12–C25 bond angle observed at 1534, and 1168cm as a mixed with ipb HCC RA and at
1
26.4° for 1 was predicted at 125.9° for 1 and at 124.8° for 1400 and 818cm− as contaminated with the νNC mode. It
1

4
Journal of Chemical Research 00(0)
Figure 1. The optimized structures of 1 and 2 at the B3LYP/6–311+G(d,p)/LANL2DZ level in CHCl3.
is challenging to predict the NC stretching modes because approachesto(δ)tetramethylsilane(TMS)[δ =σ –σ ].
iso
TMS
iso
these modes are generally coupled with C–C stretching The observed NMR spectra of both compounds are given in
modes and with the other stretching modes of the unsatu- Figures S4(a)–(d). The chemical shifts were simulated in
rated ring. In our previous study, the νNC stretching mode CHCl and recorded in CDCl and can be found in Table
3
3
of a benzimidazolium ligand was observed at 1553– S2. The correlation equations obtained from regression
−
1
−1 38
1
464cm and was predicted to be at 1586–1458cm .
analysis are given in the supplementary material (Table S2).
−
1
Here, the observed peaks at 1616cm with a strong IR Accordingly, it can be said that the observed and simulated
intensity for 1 was assigned at 1619cm (58%). The νNC chemical shifts of both compounds are very comparable
modes for 2 were observed at 1426, 1396, 1377, 1212, with each other; the regression coefficients with regard to
190, and 800cm and assigned at 1414, 1400, 1379, 1211, the C isotropic shifts for compounds 1 and 2 were calcu-
186, and 813cm , in addition to the assigned modes at lated as R =0.9942 and R =0.9939, respectively, whereas
−
1
−
1
13
1
1
1
−
1
2
2
−
1
1
534, 1446, and 1441cm . Here, the electropositive metal
H isotropic shifts for these compounds were predicted as
2
2
center caused the negative shifts because it attracts electron R =0.8786 and R =0.9835, respectively, in CHCl (Table
3
3
9
density. In Table S1, it can be seen that the assigned S2(b)).
−
1
modes at 1446 and 1186cm for 2 are predicted as a pure
Accordingly, the characteristic sharp singlet for the
νNC mode, and the remaining assigned modes are contami- acidic NCHN proton of 1 was observed at 11.75ppm in the
1
nated with the other vibrational modes.
H NMR spectrum. The absence of this peak was also
1
3
In this study, the methyl group symmetric bending proof of the formation of Ag(I)–NHC 2. The C NMR
umbrella, νCH) for compounds 1 and 2 was observed at spectrum of NHC ligand 1 exhibited the characteristic sig-
441 and 1439cm , respectively. Moreover, the corre- nal of the NCHN carbon at 137.4ppm. As reported in the
sponding mode for two compounds was assigned at literature,
carbene because of the fluxional behavior of the NHC
60%)–1438cm (74%) for 2. In the literature, the νCH complexes.
(
1
−
1
4
2–44
this peak was not observed for the Ag–
−
1
−1
−1
1
(
(
443cm (72%)–1435cm (80%) for 1, and at 1439cm
−
1
45–47
Furthermore, the chemical shifts of the
−
1,38
umbrella) mode has been observed at 1424cm
and it is acidic NCHN proton of the benzimidazolium ligand deriv-
−
1 38
48
49
predicted at the B3LYP level as 1368 and 1414cm . The ative has been reported at 11.04 and 11.25ppm. In a
scissoring modes (for σC16–H2 and σC25–H2) of the recent study, it was reported that the carbon atom chemical
methylene group for compounds 1 and 2 were computed in shifts for benzimidazole complexes were reported in the
the ranges of 1527–1477 and 1444–1349cm , respectively, range of 142.6–149.5ppm. As expected, the unsaturated
and were observed at 1489 and 1478cm for 1 and at ring C shifts (atom nos. 1–6 and13) for compounds 1
478cm for 2. Moreover, the twisting modes for the same and 2 occurred in the ranges of 116.1–137.4 and 116.1–
bonds were determined at 1549–1263cm for 1 and at 137.5ppm, whereas they were simulated in the ranges of
441–1231cm for 2, the wagging modes in the range of 118.1–140.4 and 118.4–142.5ppm in CHCl . Furthermore,
415–1368cm for 1 and 1441–1231cm for 2, and the the aromatic H shifts for compounds 1 and 2 occurred in
−
1
48
−
1
13
−
1
1
−
1
−
1
1
1
3
−
1
−1
1
−
1
rocking modes were in the range of 984–969cm for 1 and the NMR spectra between 7.64–11.75 and 7.39–7.71ppm,
268–700cm for 2. Thus, not only methyl and methylene respectively, whereas these shifts were simulated at 7.95–
−
1
1
groups but also the other vibrational modes were in good 9.40 and 7.64–7.81ppm (CHCl ), respectively. Here, it is
3
agreement with both the experimental values and previous worth mentioning that the methylene (C16 and C25) and
1
3
reports.
methyl groups (C20 and C29) were responsible for the C
NMR spectral peaks at 53.5 and 19.7ppm for 1 and at 55.5
and 19.7ppm for 2, respectively. Also, the methylene
group protons of these compounds produced the peaks at
NMR spectral analysis
The NMR shifts for compounds 1 and 2 were obtained 5.32 ppm (H27 and H28) for 1 and at 4.99–5.31ppm (H18
4
0,41
using the gauge-independent atomic orbital (GIAO)
and H19) for 2.

Serdaroğlu et al.
5
Table 2. The calculated quantum chemical parameters for 1
and 2.
Natural bond orbital (NBO) analysis
The natural bond orbital analysis and second-order pertur-
bative theory results defined by Weinhold et al.
5
0,51
Gas
CHCl3
are
increasingly used to elucidate the possible intramolecular
interactions for a specific organic or inorganic molecular
system via the prediction of the electronic parameters such
as the stabilization energy (E ), the donor/acceptor orbital
occupancy (qi/qj), the donor and acceptor orbital energies
1
2
1
2
HOMO (-I)
LUMO (-A)
ΔE (energy gap)
Χ
Η
Ω
ΔNmax
−0.191
−0.086
2.837
−3.767
1.419
−0.228
−0.234
−0.076
4.293
−4.216
2.147
−0.255
−0.056
5.422
−4.224
2.711
(
2)
−0.067
4.400
−4.013
2.200
3.660
1.824
(
εi and εj), and off-diagonal Fock matrix element (Fij). In
this study, NBO analysis was applied to elucidate and com-
pare the significant intramolecular interactions of the stud-
ied ligand and complex molecules (Table S3).
5.002
2.656
4.139
1.964
3.291
1.558
From Table S3, the possible numbers of intramolecular
HOMO: highest occupied molecular orbital; LUMO: lowest unoccupied
interactions for 1 are higher than for 2. Accordingly, the molecular orbital; I: ionization energy; A: electron affinity; Χ: electronic
chemical potential; H: global hardness; Ω: electrophilicity index; ΔN
charge transfer capability.
The HOMO and LUMO energies are in au; the other parameters are
:
most robust resonance interaction between the donor–
max
acceptor orbital was determined as LP(1) N11→π* N12–
(2)
C13 for 1 (E =88.76kcal/mol) and π C2–N12→π* given in eV.
(
2)
N11–C13 for 2 (E =37.84kcal/mol), respectively, which
means that a significant electron density will be present on
the antibonding π* N12–C13 orbital for compound 1 in
comparison with the same bond for compound 2. In other
words, the electron delocalization for compound 1 is higher
than that of compound 2, which causes the N12–C13 bond
length for compound 1 to be smaller in comparison to the
same bond for compound 2. Here, it is worth remembering
that the bond lengths of compounds 1 and 2 were calculated
changed as 1 (0.086au)>2 (0.067au) in the gas and 1
(0.076au)>2 (0.056au) in CHCl . Besides, the energy gap
3
value of each compound rose with an increase in the polar-
ity of the stimulation media. As far as the energy gap values
in both the vacuum and the polar environment are con-
cerned, it can be observed that intermolecular interactions
for 2 are more likely than in 1 because the ΔEgap for the
compounds is calculated as 2 (5.422eV)>1 (4.293eV) in
as 1.332 and 1.357Å, respectively. Moreover, the E(2) value
CHCl and as 2 (4.400eV)>1 (2.837eV) in the gas phase.
of the resonance interaction occurring in the benzene ring
of 1 was calculated in the range of 15.40 and 22.54kcal/
mol; the lowest energy interaction is predicted as π C1–
C2→π* N12–C13 and the highest energy interaction is
estimated as π C5–C6→π* C1–C2. However, the π C1–
C2→π* C3–C4 interaction contributing to the stabilization
energy for 2 does not have as much energy as the other
interactions occurring in this compound. From Table S3,
the highest contribution to the stabilization energy for the
benzene ring of 2 has been estimated as then π C5–C6→π*
C3–C4 resonance interaction with an energy of 19.27kcal/
mol and a remarkable orbital occupancy. It can also be seen
from Table S3 that there is an anomeric interaction (n→σ*)
3
However, it can be said that compound 2 is harder than
compound 1 for both phases, as expected. As seen from the
MEP diagrams and the net charge analysis, compound 2 is
more acidic than compound 1 because of the electroposi-
tive Ag atom. It is well known that the electron acceptors
are Lewis acids and that electron donors are the Lewis
5
6
bases. In this study, the electrophilicity index values of
the compounds in the CHCl (condensed) phase also sup-
3
port the relative acidic characterization. In Table 2, com-
pound 1 (5.002eV) has a more electrophilic character than
compound 1 (3.660eV) in the gas phase as well as in CHCl3
phase. Furthermore, compound 1 (2.656 eV) has more
capability of charge transfer than compound 2 (1.824eV) in
for 1 of 12.02kcal/mol (ED =0.03647e) for the intramo-
j
5
7–60
the gas phase. It is well known
that the ΔEgap has been
lecular charge transfer from a quite polarizable donor
*
commonly used to provide information on the kinetic sta-
bility and reactivity of related molecular systems. Thus, the
nucleophilicity of compound 2 is greater than compound 1,
which can be the reason for the anticancer activity of com-
pound 2.
orbital LP(4) Cl to the antibonding orbital σ O38–H40.
Moreover, the polarity of this orbital has been reduced by
the presence of the Ag atom of 2, and the hybridization of
3
.52
the LP(4) Cl orbital has been calculated to be sp . An
important interaction occurring in 2 is that of LP(5)
Ag→π* N11–C13 with a stabilization energy of 5.06kcal/
The MEP plots also imply the electrophilic and nucleo-
6
1
philic sites. The positive potential is specified with a
blue color which demonstrates the electrophilic attack
center, whereas the negative potential is visualized by red,
indicating the nucleophilic attack center. In Figure 2, the
mol (ED =1.97270).
i
Frontier molecular orbital analysis
FMO investigations have been widely used to provide MEP plot for 1 shows that the negative potential is mostly
information on the chemical stability and reactivity ten- due to the chloride ion and the water molecule and that the
dency of molecular systems via evaluation of the quantum positive potential regions are mainly over the two N atoms
5
2–55
chemical tensors.
analysis for compounds 1 and 2.
Table 2 shows the results of the FMO belonging to the heterocyclic part of the compound.
Similarly, the red color for 2 seems to be mostly over the
Accordingly, the ionization energy of the compounds Cl atom, but it should also be noted that the medium sized-
changed as 2 (0.228au)>1 (0.191au) in the gas phase and electrostatic potential with the orange color, implying the
2
(0.255au)>1 (0.234au) in CHCl . The electron affinity electrophilic center, is concentrated on the aromatic part of
3

6
Journal of Chemical Research 00(0)
Figure 3. dnorm mapped on the Hirshfeld surface for visualizing
the intermolecular contacts of compound 1.
specific molecular system. In this context, the two-dimen-
sional (2D) histograms, known as fingerprint plots, are
used to explain the types of intermolecular interactions and
6
2,63
show the relative region of the related interactions.
Figure 3 shows the Hirshfeld surfaces for 1 generated
using Crystal Explorer (version 17.5), which uses the crys-
64
tallographic information file (CIF) file as the input. Then,
Hirshfeld surfaces are visualized over the dnorm ranges from
−0.4522 to 1.3003Å to give details of the interactions.
Accordingly, the most effective interactions, which occurred
between the oxygen (O) and chloride (Cl) atoms, are marked
as bright red areas. Furthermore, Figure 4 (the 2D finger-
print plots) illustrate the possible contributions of the inter-
molecular interactions to the Hirshfeld surfaces. Long
spikes are characteristic of hydrogen bonds, which represent
Figure 2. HOMO and LUMO (isoval: 0.02), MEP (isoval:
the H···Cl/Cl···H type interactions. The left spike (near the de
0
.0004) plots, and the NBO charges for selected atoms of
compounds 1 and 2 in CHCl .
axis) represents the interaction of the molecule as a donor,
3
HOMO: highest occupied molecular orbital; LUMO: lowest unoccupied
molecular orbital; MEP: molecular electrostatic potential; NBO: natural
bond orbital.
while the other represents as an acceptor. In addition to this
interaction, there are two pairs of little wings of the H···C/
C···H type, which represent the C–H···pi type interactions.
These C–H···pi type interactions are not strong enough to
warrant extensive discussion herein.
2
and the blue color, indicating the nucleophilic center, is
over the remaining part of compound 2. Also, Figure 2
shows the essential net charges obtained from the natural
bond orbital calculations; the full atomic charges for both
In vitro anticancer activities
compounds are given in Table S4. Here, the natural atomic In this study, three different cell lines were used to deter-
charge calculations revealed that the positive charge was mine the anticancer activities of ligand 1 and complex 2.
located on the electropositive Ag atom as expected; the DU-145 cells are androgen insensitive with high metastatic
net atomic charges for the Cl atoms of compound 2 were potential and do not express prostate-specific antigen
calculated as +0.517e and −0.761e. However, the net (PSA). MCF-7 breast cancer cells are ER(+). L-929 non-
charge for the Cl atom of compound 1 was predicted as cancer cells were used to determine the toxicities of ligand
−
0.910e. The net charges of the N atoms in compounds 1 1 and complex 2 in normal cells. The evaluation of the
and 2 were calculated as −0.367e and −0.426e, respec- effect of ligand 1 and complex 2 on cancer cell viability
tively. Furthermore, the charge distribution over the imi- was applied using the MTT assay at 24, 48, and 72h.32
dazoline moiety of compound 2 changed due to the Figure 5(a)–(f) shows the dose and time-dependent antican-
presence of the electropositive Ag atom, and the N atom cer activities of ligand 1 and complex 2 toward the cancer
charges for compound 2 are more negative than those of cells and non-tumorigenic cells. The IC (concentration of
5
0
compound 1.
the test compound to achieve 50% of cell death) values for
the compounds are listed in Table 3 for all the cell lines.
Although the IC values of ligand 1 against all the tested
5
0
Hirshfeld surface analysis
cell lines were >20µM at all the time points, complex 2
Hirshfeld surfaces provide a useful perspective to represent showed different IC values depending on the time and cell
5
0
the intermolecular interactions in the crystal structure of a line type. Complex 2 did not have IC50 values against

Serdaroğlu et al.
7
Figure 4. The 2D fingerprint plots of the title compound 1 showing all interactions with the percentage contribution to the total
Hirshfeld surface area. The parameter d is the closest internal distance from a given point on the Hirshfeld surface, while d is the
i
e
closest external contact.
DU-145 and L-929 cells at 24-h exposure, at least at doses single-crystal X-ray diffraction. NBO analysis revealed
equal to 20µM. These results showed that complex 2 had that the main contribution to the stabilization energy lower-
lower IC values compared to ligand 1. As lower IC val- ing was due to the resonance interactions for both com-
5
0
50
ues indicate higher activity, complex 2 showed higher anti- pounds; the greatest contribution to the lowering of the
cancer activity than ligand 1. The lowest IC50 values were stabilization energy was calculated as LP(1) N11→π*
(
2)
determined against MCF-7 breast cancer cells with com- N12–C13 (E =88.76kcal/mol) for 1 and π C2–N12→ π*
(
2)
plex 2 (13.6, 4.83, and 2.18µM after 24, 48, and 72h expo- N11-C13 (E =37.84kcal/mol) for 2, respectively.
sure, respectively), compared to the DU-145 and L-929 Moreover, it can be concluded that compound 2 is more
cells. Therefore, MCF-7 breast cancer cells were most sus- chemically reactive than compound 1 as it has a higher
ceptible to complex 2. The selectivity index (SI) values of ΔEgap value: the ΔEgap values for the compounds were cal-
complex 2 were calculated as >1.47, 2.6, and 2.97 against culated as 2 (5.422eV)>1 (4.293eV) in CHCl and 2
3
MCF-7 breast cancer cells and >1.2, and 1.15 against (4.400eV)>1 (2.837eV) in a vacuum. The in vitro anti-
DU-145 prostate cancer cells at 24, 48, and 72h, respec- cancer activities of the compounds were also investigated
tively. The SI values indicated that complex 2 was more against DU-145 prostate cancer cells, MCF-7 breast cancer
cytotoxic and selective against MCF-7 cells than DU-145 cells, and L-929 non-cancer cells using the MTT cell via-
cells. More importantly, complex 2 had higher IC50 values bility assay for 24, 48, and 72 h. The results showed that
for L-929 normal cells and was more cytotoxic toward
DU-145 and MCF-7 cancer cells. Therefore, complex 2
demonstrated selectivity between both prostate and breast
cancer cells as well as between healthy and cancer cells.
Although ligand 1 had no anticancer activity in any cell
lines, complex 2 showed dose and time-dependent antican-
cer activity against all cell lines. More importantly, com-
plex 2 displayed lower anticancer activities on L-929
non-cancer cells than cancer cells.
complex 2 demonstrated time and dose-dependent antican-
cer activities toward DU-145 and MCF-7 cancer cells. The
results also indicated that ligand 1 had lower anticancer
activity against cancer cells compared to the Ag(I) complex
2
. As the lower IC values indicate higher anticancer activ-
50
ity, complex 2 displays the highest anticancer activity
against MCF-7 cell lines at all time points studied. More
importantly, complex 2 displayed lower anticancer activity
toward L-929 non-cancer cells than cancer cells.
Conclusion
Experimental
This paper has focused on the synthesis of benzimidazo-
lium salt and its Ag(I)–NHC complex, and their structural
Materials and measurements
determination, theoretical studies, the comparison of in All experiments were performed under argon in flame-
vitro anticancer activities of both compounds, and the dried glassware using standard Schlenk techniques. All rea-
Hirshfeld surface analysis of the benzimidazolium salt. gents were purchased from Sigma-Aldrich Co. (Dorset,
Both compounds were characterized by spectroscopic tech- UK). The solvents used were purified by distillation over
niques in addition to characterizing compound 1 by appropriate drying agents and were transferred under argon.

8
Journal of Chemical Research 00(0)
Figure 5. The dose and time-dependence of the in vitro anticancer activities of ligand 1 and complex 2 against DU-145 and MCF-7
cancer cells and L-929 non-cancer. Control cells were treated with DMSO. Data are representative of the mean of three separate
experiments performed in triplicate and are reported as SEM. (a), (c), (e) in vitro anticancer activities of ligand I against DU-145,
MCF-7 cancer cells and L-929 non-cancer cells, respectively. (b), (d), (f) in vitro anticancer activities of complex 2 against DU-145,
MCF-7 cancer cells and L-929 non-cancer cells, respectively.
DMSO: dimethyl sulfoxide; SEM: standard error mean.
*p<0.05 versus control, **p<0.005 versus control, ***p<0.0005 versus control, and ****p<0.0001 versus control.
Melting points were determined using an Electrothermal 1,3-Bis-(2-methyl-2-propenyl)
100 melting point detection apparatus in capillary tubes, benzimidazolium chloride (1)
and the melting points are uncorrected. FTIR spectra were
9
−
1
Benzimidazole (10 mmol) was added to a solution of
NaH (10 mmol) in dry tetrahydrofuran (THF) (30 mL)
and the mixture was stirred for 1 h at room temperature.
2-Methyl-2-propenylchloride (10.1 mmol) was added
dropwise and the obtained solution was heated for 24 h at
recorded in the range of 400–4000 cm on a Perkin Elmer
1
13
Spectrum 100 FTIR. H NMR and C NMR spectra were
obtained using a Bruker As 400 Mercury spectrometer
1
13
operating at 400MHz ( H) and 100MHz ( C) in CDCl
3
1
with TMS as the internal reference. H NMR peaks are
labeled as singlet (s) and multiplet (m). Chemical shifts and
coupling constants are reported in ppm and Hz, respec-
tively. All the measurements were taken at room tempera-
ture using freshly prepared solutions.
6
0 °C. Next, the solvent was removed under vacuum.
Dichloromethane (50 mL) was added to the solid. The
mixture was filtered, and the obtained clear solution was
concentrated under vacuum. The remaining solution was
distilled to give 1-(2-methyl-2-propenyl)benzimidazole.
1
2
-(2-Methyl-2-propenyl)benzimidazole (1 mmol) and
-methyl-2-propenylchloride (1 mmol) were stirred in
Synthesis
NHC ligand 1 and its Ag(I)–NHC complex 2 were prepared dimethylformamide (DMF) (5 mL) for 24 h at 80 °C, and
45
under an argon gas atmosphere according to the literature.
the product precipitated. The solution was filtered and

Serdaroğlu et al.
9
the solid was rinsed with diethyl ether and dried under 24h in the dark. Next, the mixture was filtered through
vacuum. The crude product was recrystallized from Celite. The clear filtrate was evaporated under vacuum to
dichloromethane/diethyl ether. Yield: 84%, m.p. 168– afford the crude product, which was then recrystallized
−
1 1
1
69 °C. IR: ν(CN): 1552 cm . H NMR (400 MHz, CDCl ): from dichloromethane/diethyl ether. Yield: 79%, m.p. 151–
3
−
1
1
δ = 1.90 (s, 6H, NCH C(CH )CH ), 4.99 (s, 2H, NCH C 153 °C, IR: ν(CN): 1378 cm . H NMR (400 MHz,
2
3
2
2
(
CH )CH ), 5.14 (s, 2H, NCH C(CH )CH ), 5.32 (s, 4H, CDCl ): δ=1.73 (s, 3H, NCH C(CH )CH ), 1.80 (s, 3H,
3 2 2 3 2 3 2 3 2
NCH C(CH )CH ), 7.64–7.65 and 7.75–7.76 (m, 4H, NCH C(CH )CH ), 4.83 (s, 1H, NCH C(CH )CH ), 4.98
2
3
2
2
3
2
2
3
2
1
3
NC H N), 11.75 (s, 1H, NCHN). C NMR (100 MHz, (s, 1H, NCH C(CH )CH ), 4.99 (s, 2H, NCH C(CH )CH ),
6
4
2
3
2
2
3
2
CDCl ): δ = 19.7 (NCH C(CH )CH ), 53.5 (NCH C(CH ) 5.03 (s, 1H, NCH C(CH )CH ), 5.14 (s, 1H, NCH C(CH )
3
2
3
2
2
3
2
3
2
2
3
CH ), 113.8 (NCH C(CH )CH ), 137.4 (NCHN), 116.1, CH ), 5.31 (s, 2H, NCH C(CH )CH ), 7.37–7.40, 7.45–
2
2
3
2
2
2
3
2
13
1
27.3, and 131.5 (ArC) and 144.3 (NCH C(CH )CH ).
7.48, 7.61–7.64, and 7.69–7.73 (m, 4H, NC H N). C NMR
2
3
2
6 4
(
100MHz, CDCl ): δ=19.7 and 20.0 (NCH C(CH )CH ),
3 2 3 2
Chloro[1,3-bis-(2-methyl-2-propenyl)
53.6and55.5(NCH C(CH )CH ),112.1(NCH C(CH )CH ),
113.8 (NCH C(CH )CH ), 139.1 (NCH C(CH )CH ), 144.3
2 3 2 2 3 2
2 3 2 2 3 2
benzimidazole-2-ylidene] Ag(I) (2)
(
NCH C(CH )CH ), 114.5, 116.1, 124.3, 127.2, 133.9, and
2 3 2
Asolution ofAg O (0.5mmol) and of NHC (1mmol) ligand
2
137.5 (ArC), Ag–C (carbene) not observed.
1
in CH Cl (25mL) was stirred at room temperature for
2 2
X-ray crystallography and refinement of 1
Table 3. In vitro anticancer activities of ligand 1 and complex
against DU-145, MCF-7, and L-929 cells.
2
Single-crystal X-ray diffraction data of the NHC ligand
were collected at room temperature on a Rigaku–Oxford
Xcalibur diffractometer with an electro-optical system
IC50 (µM)a
Ligand 1
Cell lines
Time
h)
(
Complex 2
(
EOS)-charge-coupled device (CCD) detector using
DU-145b
graphite-monochromatedMoKαradiation(λ = 0.71073 Å)
24
>20
>20
>20
>20
>20
>20
>20
>20
>20
>20
Pro
65
with CrysAlis software. Data reduction and analyti-
cal absorption correction were performed using the
4
7
8
2
6.20±0.06
5.61±0.03
13.6±0.25
4.83±0.02
2.18±0.01
>20
MCF-7b
L-929c
24
Pro
66
67
CrysAlis program. Utilizing OLEX2, the structure
was solved using the intrinsic phasing method with
4
7
8
2
2
SHELXT and refined by full-matrix least squares on F in
68,69
24
SHELXL.
Anisotropic thermal parameters were
4
7
8
2
12.6±0.19
6.48±0.18
applied to all non-hydrogen atoms. Hydrogen atoms were
placed using standard geometric models and with their
thermal parameters riding on those of their parent atoms
MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; SEM:
standard error mean.
(
C–H = 0.93–0.96–0.97 Å). The details of the crystal data
Each IC50 value represents the mean±SEM of three independent
and structure refinement of the title compound are given
in Table 4.
Crystallographic data as .cif file for the structure reported
in this paper have been deposited at the Cambridge
Crystallographic Data Center with CCDC 1822823.
experiments (nine replicates).
a
Cell viability after treatment for 24, 48, and 72h was determined by
MTT staining as described in section “Experimental” (µM).
b
Cancer cells.
c
Non-cancer cells.
Table 4. Crystallographic data and structure refinement parameters for 1.
Empirical formula
C H N OCl
15 21 2
−
1
Formula weight (gmol )
Temperature (K)
280.79
294(2)
Crystal system, space group
a, b, and c (Å)
Triclinic, P-1
9.1633(8), 9.7958(8), and 9.9415(9)
α, β, and γ (°)
V (Å )
63.630(9), 78.612(7), and 78.184(7)
776.78(12)
3
Z
2
−
3
Densitycalc (mgm )
Absorption coefficient (mm )
F(000)
1.200
0.241
300
−
1
Crystal size (mm)
Limiting indices
Reflections collected/independent
Parameters
0.520 × 0.255 × 0.225
−10 11, −12 10, −12 12
4756/3139
177
1.028
2
Goodness-of-fit on F
Final R indices [I>2σ(I)]
R indices (all data)
Largest diff. peak and hole (eÅ )
R =0.053, wR =0.110
1
2
R =0.085, wR =0.129
1
2
−
3
−0.261/0.303

1
0
Journal of Chemical Research 00(0)
LANL2DZ basis set using Gaussian 09W software73 and
verified by the non-negative in frequency. The optimized
structures of the compound were used for further calcula-
tions in both a vacuum and in CHCl . The vibrational
3
7
4
modes of both compounds have been scaled with factor of
.9688 for high frequencies and 1.0189 for low frequencies
and assigned by PED analysis using the vibrational energy
0
7
5
distribution analysis (VEDA) program. NMR chemical
3
6,37
shifts of both compounds were obtained using the GIAO
approach by subtracting the shielding constants of TMS.
5
0,51
52–55
NBO
and FMO
analyses were conducted to investi-
gate the intramolecular interactions and biological activity
tendency of both compounds. FMO amplitudes and MEP
plots provided information on the possible reactive regions
of the compounds, and this was visualized using GaussView
Figure 6. Atom-by-atom superimposition of the calculated
structure (red) on the X-ray structure (green) for 1.
7
6
6
.0.16. All quantum chemical calculations in the polar
Table 5. Hydrogen-bonding interactions (Å, °) for
compound 1.
environment were performed using the polarized contin-
uum model (PCM).
7
7,78
D–H∙∙∙A
D–H
H∙∙∙A
D∙∙∙A
D–H∙∙∙A
Cell cultures
O1w–H1wA∙∙∙Cl1i
O1w–H1wB∙∙∙Cl1
C8–H8B∙∙∙Cl1
C12–H12A∙∙∙Cl1
0.85
0.85
0.97
0.97
0.97
2.35
2.58
2.75
2.78
2.72
3.182(3)
3.187(3)
3.668(3)
3.687(3)
3.681(3)
168
129
159
156
173
ii
The human cancer cell lines DU-145 (HTB-81, human pros-
tate carcinoma), and MCF-7 (HTB-22, human breast adeno-
carcinoma), were purchased from American Type Culture
Collection (ATCC) (Manassas, VA, USA). L-929 (non-
cancer cells adipose from mouse) were purchased from
European Collection of Animal Cell Culture (ECACC,
Salisbury, UK). Eagle’s minimum essential medium
ii
i
iii
C12–H12B∙∙∙Cl1
Symmetry codes: (i) −1+x, y, z; (ii) 1−x, 2−y, 1−z; and (iii) 1−x, 1−y,
−z.
1
(
EMEM, 30-2003), fetal bovine serum (FBS, 30-2020),
Figure 6 displays the overlay of the X-ray and calcu- and penicillin and streptomycin (30-2300) were pur-
lated molecules in the asymmetric unit, which reveals that chased from ATCC. Dulbecco’s modified Eagle’s medium
their structures are virtually equivalent. The root-mean- (DMEM, D6429) and trypsin-ethylenediaminetetraacetic
square deviation (RMSD) value was found to be 0.356Å acid (EDTA) solution (T-3924) were purchased from
with inversion and 0.384Å without inversion. The crystal Sigma-Aldrich (Sigma-Aldrich Chemie GmbH, Steinheim,
structure of the title molecule is consolidated by hydrogen Germany).
bonds involving the chloride anion, propenyl moieties of
the cation, and the water molecule, which are linked
through an intricate H-bonding network consisting of two
MTT assay
Ow–Hw∙∙∙Cl and three C–H∙∙∙Cl interactions (Table 5). The MTT method was used to determine the anticancer
3
2
Accordingly, the chloride anion behaves as an H-bond activity of ligand 1 and complex 2. The DU-145 cell line
acceptor in the crystal structure, resulting in the formation was cultured in EMEM; MCF-7 and L-929 cells were cul-
of the one-dimensional supramolecular array (see Figure tured in the DMEM supplemented with 10% FBS and 1%
−
S1). Besides, the Cl ions were hydrated by forming an penicillin/streptomycin solution. All cells were cultured in
2
−
anionic hydrogen-bonded cluster [Cl (H O) ] via the an incubator with 5% CO at 37°C. Cells were passaged
2
2
2
2
i
ii
intermolecular O1w–H1wA∙∙∙Cl1 and O1w–H1wB∙∙∙Cl1
when the confluence of the cells reached 80% or higher.
hydrogen bonds. These chloride–water tetrameric clusters Cells were seeded in a 96-well plate at a density of
5
have a rectangular-like geometry and generate a cyclic 1×10 cells/well and allowed to adhere for 24h at 37°C in
R (8) graph-set motif in Etter’s graph notation. They a CO incubator. 1μL of different concentrations (1–20µM)
2
4
70
2
ii
were also held by two cations through the C8–H8B∙∙∙Cl1
of the compounds were added to each well, and the cells
i
2
4
and C12–H12A∙∙∙Cl1 interactions to form a R (12) -type were treated for 24, 48, and 72h. Control and negative con-
hydrogen-bonded motif, as shown in Figure S2. There is trol wells were treated with culture medium and sterile
i
another tetrameric cluster formed by the C12–H12A∙∙∙Cl1 DMSO. At the end of the time points, 10μL of the MTT
iii
and C12–H12B∙∙∙Cl1 hydrogen bonds, which reveals the solution was added to each well and allowed to incubate at
2
4
R (8) graph-set notation. All these bifurcated hydrogen 37°C for a further 2h.After complete removal of the media,
bonds are responsible for the stabilization and packing in DMSO was added to each well to dissolve the formazan;
the supramolecular architecture of the crystal structure.
then, the dye plates were incubated for 15min at room tem-
perature. Optical density was measured at 570nm in
enzyme-linked immunosorbent assay (ELISA) (Biotek,
Epoch, USA). Data represent the average values of three
Density-functional theory studies
The molecular geometries of compounds 1 and 2 were opti- independent measurements with standard error means
7
1,72
mized using B3LYP
functional and the 6–311+G(d,p)/ (±SEM).

Serdaroğlu et al.
11
4
5
. Herrmann WA. Angew Chem Int Ed 2002; 41; 1290.
. Crudden CM and Allen DP. Coord Chem Rev 2004; 248:
247.
Statistical analysis
All experiments were carried out in triplicate, and the results
are expressed as means±SEM. Data were analyzed using
one-way analysis of variance and differences were con-
sidered statistically significant at *p<0.05, **p<0.005,
2
6. Díez-González S and Nolan SP. Coord Chem Rev 2007; 251:
874.
7. Nolan SP. N-heterocyclic carbenes in synthesis. London:
Wiley, 2006.
*
**p<0.0005, and ****p<0.0001. The IC50 values were
determined using statistical software, GraphPad Prism7
GraphPad Software, San Diego, CA, USA).
8
9
. Kantchev EA, O’Brien CJ and Organ MG. Angew Chem Int
Ed 2007; 46: 2768.
. DePasquale J, White NJ, Ennis EJ, et al. Polyhedron 2013;
(
5
8: 162.
Acknowledgements
1
0. Şahin N, Demir S and Özdemir İ. Arch Org Chem 2015; 2:
Dokuz Eylül University is acknowledged for the use of the
20.
Rigaku–Oxford Xcalibur EoS Diffractometer (purchased under 11. Laï R, Daran JC, Heumann A, et al. Inorg Chim Acta 2009;
University Research Grant No. 2010.KB.FEN.13). Also, the
362: 4849.
authors thank Sivas Cumhuriyet University Scientific Research 12. Van Rensburg H, Tooze RP, Foster DF, et al. Inorg Chem
Projects Department (Project No. CUBAP: EĞT-086) and İnönü
2004; 43: 2468.
University Scientific Research Projects Department (Project No. 13. Pizzolato SF, Giannerini M, Bos PH, et al. Chem Commun
FOA-2018-1135) for their financial support. All calculations were
2015; 51: 8142.
carried out at TUBITAK ULAKBIM, High Performance and Grid 14. Berardi S, Carraro M, Iglesias M, et al. Chem Eur J 2010; 16:
Computing Center (TR-Grid e-Infrastructure). In vitro anticancer
10662.
activity studies were performed at Advanced Technology 15. Rouen M, Queval P, Falivene L, et al. Chem Eur J 2014; 20:
Research and Application Center (CUTAM), Sivas Cumhuriyet
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University.
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Author contributions
2
All authors contributed to the study conception and design.
1
1
2
2
2
8. Schneider H, Schmidt D, Eichhöfer A, et al. Eur J Inorg
Chem 2017; 19: 2600.
9. Betzer JF, Nuter F, Chtchigrovsky M, et al. Bioconjugate
Chem 2016; 27: 1456.
0. Haque RA, Asekunowo PO, Razali M, et al. Heteroatom
Chem 2014; 25: 194.
1. Stachowicz J, Krajewska-Kułak E, Łukaszuk C, et al. Indian
J Pharm Sci 2014; 76: 287.
1
13
Synthesis, H NMR, C NMR, and FTIR spectra were performed
by Neslihan Şahin, Nevin Gürbüz, and İsmail Özdemir.
Crystallographic studies were performed by Duygu Barut-Celepci
and Resul Sevinçek. Density-functional theory studies were per-
formed by Goncagül Serdaroğlu. Cell culture studies were per-
formed by Serap Şahin-Bölükbaşı. The first draft of the paper was
written by Serap Şahin-Bölükbaşı, Goncagül Serdaroğlu, Neslihan
Şahin, and Duygu Barut-Celepci. All authors commented on the
paper and read and approved the final paper.
2. Jahnke CM and Hahn FE. Introduction to N-heterocyclic
carbenes: synthesis and stereoelectronic parameters.
Cambridge: RSC Publishing, 2011, p. 1.
Declaration of conflicting interests
2
3. National Library of Medicine. Genetics home reference.
Bethesda, MD: The Library.
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this 24. Safin DA, Babashkina MG, Robeyns K, et al. New J Chem
paper.
2017; 41: 8263.
2
2
2
5. Butchard JR, Curnow OJ, Garrett DJ, et al. Angew Chem Int
Ed 2006; 45; 7550.
6. Kopylovich MN, Tronova EA, Haukka M, et al. Eur J Inorg
Chem 2007; 29: 4621.
7. Buisine O, Berthon-Gelloz G, Brière J-F, et al. Chem
Commun 2005; 30: 3856.
Ethical approval
All ethical guidelines have adhered.
Funding
The author(s) received no financial support for the research, 28. Şahin N, Gürbüz N, Karabıyık H, et al. J Organomet Chem
authorship, and/or publication of this paper.
2020; 907: 121076.
2
3
3
3
3
9. Şahin N, Yıldırım İ, Özdemir N, et al. J Organomet Chem
2
020; 918: 121285.
ORCID iD
0. Çevik-Yıldız E, Şahin N and Şahin-Bölükbaşı S. J Mol
Struct 2020; 1199: 126987.
1. Trzybinski D and Sikorski A. CrystEngComm 2013; 15:
Goncagül Serdaroğlu
https://orcid.org/0000-0001-7649-9168
Supplemental material
6
808.
2. Skehan P, Storeng R, Scudiero D, et al. J Natl Cancer Inst
990; 82: 1107.
3. Şahin N, Kılıç-Cıkla I, Özdemir N, et al. Mol Cryst Liq Cryst
018; 664: 109.
Supplemental material for this paper is available online.
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