Synthesis, X-ray characterization, and in vitro biological approach of dimeric and polymeric mercury(II) complexes with α-keto stabilized sulfur ylide

Article abstract of DOI:10.1080/00958972.2018.1510493

Reaction of α-keto stabilized sulfur ylide (Me)₂SCHC(O)C₆H₄-p-CN (Y) with HgX₂ (X = Cl, Br, and I) led to the formation of new dinuclear products of the type [HgX₂(Y)]₂ (X = Cl (1), Br (2),

Full text of DOI:10.1080/00958972.2018.1510493

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Synthesis, X-ray characterization and in vitro
biological approach of dimeric and polymeric
mercury(II) complexes with α-keto stabilized sulfur
ylide
Seyyed Javad Sabounchei, Mojdeh Sadat Hashemi, Roya Karamian, Seyed
Hamed Moazzami Farida, Parviz Gohari Derakhshandeh, Robert W. Gable &
Kristof Van Hecke
To cite this article: Seyyed Javad Sabounchei, Mojdeh Sadat Hashemi, Roya Karamian, Seyed
Hamed Moazzami Farida, Parviz Gohari Derakhshandeh, Robert W. Gable & Kristof Van Hecke
(2018): Synthesis, X-ray characterization and inꢀvitro biological approach of dimeric and polymeric
mercury(II) complexes with α-keto stabilized sulfur ylide, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2018.1510493
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Synthesis, X-ray characterization and in vitro biological approach of dimeric
and polymeric mercury(II) complexes with α-keto stabilized sulfur ylide
SEYYED JAVAD SABOUNCHEI*ª, MOJDEH SADAT HASHEMIa, ROYA KARAMIANb, SEYED HAMED
MOAZZAMI FARIDAb, PARVIZ GOHARI DERAKHSHANDEHc, ROBERT W. GABLEd and
KRISTOF VAN HECKE*c
a Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 65174, Iran
b Department of Biology, Faculty of Science, Bu-Ali Sina University, P. O. Box 65175/4161, Hamedan, Iran
c XStruct, Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281-S3, B-9000
Ghent, Belgium
d School of Chemistry, University of Melbourne, Victoria 3010, Australia
Reaction of α-keto stabilized sulfur ylide (Me)2SCHC(O)C6H4-p-CN (Y) with HgX2 (X = Cl, Br
and I) led to the formation of new dinuclear products of the type [HgX2(Y)]2 (X = Cl (1), Br (2)
and I (3)). Furthermore, the reaction of the corresponding sulfur ylide (Y) with Hg(NO3)2∙H2O in
equimolar ratio, using methanol as a solvent, was shown to produce the polynuclear complex
[(Y)Hg(NO3)2]n (4). The obtained compounds were characterized using elemental analysis, IR,
1H and 13C NMR techniques. The structures of compounds Y and 1 were characterized by single-
crystal X-ray diffraction analysis. Also, in order to confirm the crystalline nature of complexes
1-3, powder X-ray diffraction (XRD) pattern was used. Likewise, the antioxidant property of the
complexes was examined by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging
which revealed the strong-to-moderate radical scavenging ability (IC50; 0.163 ± 0.004 to 0.936 ±
0.012 mg∙mL-1) of the synthesized compounds. Further, results from this study indicated that the
compounds possess moderate antibacterial activity.
Keywords: Synthesis; Sulfur ylide; Hg(II) Complexes; Single-crystal X-ray diffraction;
Antioxidant; Biological activity
1. Introduction
Sulfur ylides R2S=C(R′)(R″) which are conveniently produced by the treatment of sulfonium
salts with base have been recognized as important reagents in organic chemistry [1-6]. Because
of high stability and the ambidentate character of α-keto stabilized sulfur ylides, these
*Corresponding authors. Email: jsabounchei@yahoo.co.uk (S.J. Sabounchei); kristof.VanHecke@UGent.be
(K. van Heck)
1

compounds are a suitable choice for organometallic synthesis [7-10]. About 40 years ago,
Weleski et al. [11] reported a halide-bridged dimeric structure for the Hg(II) halide complexes
with sulfur ylides. Soon after, in 1984, Tewari et al. [12] managed to report the synthesis of a
series of transition metal complexes with various sulfur ylides without further characterization.
Sulfur ylides can coordinate to metal ions through the carbanion (C-coordinate) or the enolate
(O-coordinate) in three distinct modes: mononuclear (D or E), dinuclear (F) and multinuclear
structures (G) (scheme 1) [13-15]. Soft metal ions such as Pd(II), Pt(II), Ag(I), Hg(II), Au(I) and
Au(III) coordinate through carbon and this type of coordination is more predominant [16-18].
Whereas O-coordination dominates when the metals involved are hard, e.g., Ti(IV), Zr(IV), and
Hf(IV) [19].
Scheme 1. Canonical binding modes of (Me)2SCHC(O)C6H4-p-CN to metal ions.
Although a large spectrum of microorganisms coexists in a natural equilibrium with the human
body and living environments, uncontrolled fast thriving of microbes can lead to troublesome
problems [20, 21]. Therefore, scientists have attempted to develop materials which are capable to
prevent the bacterial growth and also to scavenge the free radicals in order to use them in
hospital equipment and industrial products such as textile, soap, detergents, household cleaner,
health and skin care products. In this context, inorganic materials have received extensive
2

interest more than organic compounds because of their outstanding advantages such as chemical
stability, thermal resistance, safe use and a long active period [22-24]. This paper includes the
synthesis, spectroscopic and structural characterization of dinuclear and polymeric complexes of
Hg(II) with sulfur ylide. In addition, we assessed in vitro antioxidant and antibacterial activities
of the synthesized complexes.
2. Experimental
2.1. Physical measurements and materials
All reactions were carried out in the air. All solvents and materials were prepared from
commercial sources and were utilized without purification. Melting points were measured with
an SMP3 apparatus. IR spectra were recorded on KBr pellets using a Shimadzu 435-U-04
1
spectrophotometer from 4000-400 cm-1. H and 13C NMR spectra were recorded on 250 MHz
Bruker and 90 MHz Jeol spectrometers in DMSO-d6 as the solvent at 25 °C. Chemical shifts (δ)
are reported relative to internal TMS (1H and 13C). Coupling constants are given in Hz.
Elemental analysis for carbon, nitrogen, hydrogen, and sulfur atoms have been confirmed by
utilizing a Perkin Elmer 2400 series analyzer. Powder X-ray diffraction (XRD) patterns were
determined with a Philips PW1730 (X-ray diffractometer with Cu as anode material, K-alpha [Å]
= 1.54184 and the generator settings 30 mA, 40 KV).
2.2. X-ray crystallography
Single-crystals of Y and 1 were obtained by continuous and gradual evaporation from DMSO.
Suitable crystals were selected and mounted on cryoloop and nylonloop with X-ray intensity data
collected at 130 K (for Y) and 100 K (for 1) on a Rigaku Oxford Diffraction Supernova Dual
Source (Cu at zero) diffractometer equipped with an Atlas CCD detector using  scans and
CuK ( = 1.54184 Å) radiation. Interpreted and integrated were the images with the program
CrysAlisPro [25]. With the use of Olex2 [26], the structures were solved by direct methods using
the ShelXS structure solution program and refined by full-matrix least-squares on F2 using the
ShelXL program package [27, 28]. Non-hydrogen atoms were anisotropically refined and the
hydrogen atoms in the riding mode and isotropic temperature factors were fixed at 1.2 times
U(eq) of the parent atoms (1.5 times for methyl groups).
3

2.3. Evaluation of biological activities
2.3.1. Antioxidant activity. Antioxidant activities of the complexes were evaluated by DPPH
radical scavenging as reported by Mensor et al. [29]. Briefly, 2.5 ml of different concentrations
of each sample (0.2-1 mg∙mL-1 in DMSO) were added to 1 ml of 0.3 mM DPPH solution and
incubated 30 min at room temperature under dark. The reduction of free radicals was measured
by reading the absorbance at 517 nm. Ascorbic acid and quercetin were used as reference
standards. The antioxidant activity of each sample was calculated from the following formula:
DPPH free radical scavenging (%) = [1 – (As – Ab)/Ac] × 100
where As is the absorbance of the reaction mixture containing 2.5 mL of sample + 1 mL of
DPPH, Ab is the absorbance of the reaction mixture containing 2.5 mL of sample + 1 mL
methanol and Ac is the absorbance of the control sample containing 1 mL of DPPH + 2.5 mL
methanol. Also, the IC50 value, defined as the concentration of the sample leading to 50%
reduction of the initial DPPH concentration, was calculated from the linear regression plot of the
concentration of the test sample against the mean percentage of the antioxidant activity [30].
2.3.2. Antibacterial activity. The synthesized complexes were screened for their antibacterial
activities against Escherichia coli, Salmonella typhimurium, Klebsiella oxytoca, and Shigella
dysenteriae as Gram-negative bacteria and Listeria monocytogenes, Bacillus subtilis, Bacillus
cereus and Staphylococcus aureus as Gram-positive bacteria. The complexes were dissolved in
DMSO to a final concentration of 1 mg∙mL-1 and filtrated using a 0.45 µm Millipore. All
complexes were carried using 10 mL of a suspension containing 1.5×108 bacteria mL-1 and
spread on nutrient agar medium. The antibiotics Penicillin, Ampicillin, Vancomycin and
Tetracycline were used as positive reference standards, and negative controls were prepared by
using DMSO. The inhibition zone diameter and the amount of swelling from the edge of each
disc in the plate are given in mm.
2.3.3. Statistical analysis. All data obtained from both antioxidant and antibacterial assessments
were performed in triplicate. Data were analyzed using a one-way ANOVA and Duncan test and
expressed as the mean ± SD. All significance tests were set at P ≤ 0.05, and the statistics were
4

analyzed using the SPSS software (IBM Corp. Released 2013. IBM SPSS Statistics for
Windows, Version 22.0. Armonk, NY: IBM Corp.). In order to depict the synthesized
compounds grouping, cluster analysis (CA) was performed for IC50 values of the compounds
based on Euclidean similarity index using Unweighted Pair-Group Method with Arithmetic
Means (UPGMA) method. Visualization of CA data was performed using PAST software.
2.4. Synthesis
2.4.1. Synthesis of [(Me)2SCH2C(O)C6H4-p-CN]Br (S). 0.11 g (0.5 mmol) of 2-bromo-4׳-
cyanoacetophenone was dissolved in 15 mL acetone. Then, to the solution was added 0.09 g
(1.5 mmol) of dimethyl sulfide. The resulting mixture was allowed to be stirred for 15 h. After
the solvent evaporation, being washed with acetone, white sediment was obtained. Yield: 90%
1
13
(0.13 g); decomposition at 158-162 °C. The product was characterized on the basis of H, C
NMR and CHNS analysis data that well fitted its structure. Anal. Calc. for C11H12SBrON (%): C,
46.16; H, 4.23; S, 11.20. Found: C, 46.32; H, 4.39; S, 11.36. IR (KBr disk), ν (cm-1): 1688
(C=O); 831 (S+-C-) and 2234.76 (CN). 1H NMR, DMSO-d6, δ (ppm): 3.02 (s, 6H, S(CH3)2); 5.64
(s, 2H, CH2); 7.92-8.23 (m, 4H, Ph). 13C NMR, DMSO-d6, δ (ppm): 26.64 (s, S(CH3)2); 54.92 (s,
CH2); 115.35 (s, CN); 116.21 (s, Ph); 117.09 (s, Ph); 118.82 (s, Ph); 119.04 (s, Ph); 195.88 (s,
CO).
2.4.2. Synthesis of (Me)2SC(H)C(O)C6H4-p-CN (Y). 0.18 g (0.62 mmol) of S was added to
25 mL of NaOH (10%) aqueous solution and then stirred at 25 °C for 15 min. The ylide Y was
extracted, washed and dried. Yield: 70% (0.09 g); decomposition at 165-166 °C. The product
was characterized on the basis of 1H, 13C NMR, CHNS analysis data that well fitted its structure.
Anal. Calc. for C11H11NOS (%): C, 64.36; H, 5.40; S, 15.62. Found: C, 64.42; H, 5.46; S, 15.69.
1
IR (KBr disk), ν (cm-1): 1572 (C=O), 861.31 (S+-C-) and 2225.61 (CN). H NMR, DMSO-d6,
13
δ (ppm): 2.95 (s, 6H, S(CH3)2); 4.31 (s, 1H, CH); 7.24-7.81 (m, 4H, Ph). C NMR, DMSO-d6,
δ (ppm): 26.75 (s, S(CH3)2); 53.25 (s, CH); 112.55 (s, CN); 118.94 (s, Ph); 126.42 (s, Ph);
131.80 (s, Ph); 145.01 (s, Ph); 180.33 (s, CO).
2.4.3. Synthesis of the complexes. General procedure: 0.2 g (1 mmol) of the sulfur ylide (Y)
was added to 15 mL of a methanol solution of HgX2 (X = Cl, Br and I) (1 mmol, 5 mL) or
5

Hg(NO3)2∙H2O (1 mmol, 5 mL) and stirred for 4 h at room temperature. The formed precipitate
was filtered, washed with diethyl ether and dried.
2.4.3.1. Data for [(Y)HgCl2]2 (1). Yield 0.2 g, 92%. Anal. Calc. for C22H22Cl4Hg2N2O2S2 (%): C,
27.71; H, 2.33; S, 6.73; N, 2.94. Found: C, 27.80; H, 2.42; S, 6.80; N, 3.03. Decomposition at
1
208-210 ºC. IR (KBr disk), ν(cm-1): 1655 (CO); 856 (C--S+) and 2237 (CN). H NMR,
13
DMSO-d6, δ (ppm): 2.91 (s, 6H, S(CH3)2); 5.49 (s, 1H, CH); 7.91-8.11 (m, 4H, Ph). C NMR,
DMSO-d6, δ (ppm): 27.12 (s, S(CH3)2); 64.58 (s, CH); 115.22 (s, CN); 118.60 (s, Ph); 128.63 (s,
Ph); 132.93 (s, Ph); 139.13 (s, Ph); 190.56 (s, CO).
2.4.3.2. Data for [(Y). HgBr2]2 (2). Yield 0.2 g, 89%. Anal. Calc. for C22H22Br4Hg2N2O2S2 (%):
C, 23.36; H, 1.96; S, 5.67; N, 2.48. Found: C, 23.54; H, 2.14; S, 5.85; N, 2.66. Decomposition at
200-202 ºC. IR (KBr disk): ν(cm-1) 1653 (CO); 745 (C--S+) and 2237 (CN). 1H NMR, DMSO-d6,
13
δ (ppm): 2.89 (s, 6H, S(CH3)2); 5.43 (s, 1H, CH); 7.92-8.11 (m, 4H, Ph). C NMR, DMSO-d6,
δ (ppm): 27.21 (s, S(CH3)2); 64.52 (s, CH); 114.98 (s, CN); 118.67 (s, Ph); 128.60 (s, Ph);
132.90 (s, Ph); 139.69 (s, Ph); 189.58 (s, CO).
2.4.3.3. Data for [(Y).HgI2]2 (3). Yield 0.2 g, 87%. Anal. Calc. for C22H22I4Hg2N2O2S2 (%): C,
20.03; H, 1.68; S, 4.86; N, 2.12. Found: C, 20.21; H, 1.82; S, 5.04; N, 2.3. Decomposition at
1
186-188 °C. IR (KBr disk), ν(cm-1): 1640 (CO); 825 (C--S+) and 2234 (CN). H NMR,
13
DMSO-d6, δ (ppm): 2.90 (s, 6H, S(CH3)2); 5.32 (s, 1H, CH); 7.74-8.12 (m, 4H, Ph). C NMR,
DMSO-d6, δ (ppm): 27.35 (s, S(CH3)2); 64.22 (s, CH); 114.65 (s, CN); 118.57 (s, Ph); 128.57 (s,
Ph); 132.85 (s, Ph); 140.37 (s, Ph); 188.35 (s, CO).
2.4.3.4. Data for [(Y). Hg(NO3)2]n (4). Yield 0.2 g, 91%. Anal. Calc. for C11H11O7N3SHg (%): C,
24.93; H, 2.09; S, 6.05; N, 7.93. Found: C, 25.09; H, 2.27; S, 6.23; N, 8.11. Decomposition at
193-195 °C. IR (KBr disk), ν(cm-1): 1661 (CO); 1384 (NO); 858 (C--S+) and 2234 (CN).
1H NMR, DMSO-d6, δ (ppm): 2.71, 2.98 (s, 6H, S(CH3)2); 5.51- 5.97 (d, 1H, CH); 7.61-8.33 (m,
4H, Ph). 13C NMR, DMSO-d6, δ (ppm): 26.95 (s, S(CH3)2); 60.36, 67.55 (s, CH); 115.23 (s,
CN); 114.10 (s, Ph); 121.18 (s, Ph); 121.65 (s, Ph); 130.86 (s, Ph); 135.8 (s, Ph); 160.15 (s, Ph);
192.10, 194.57 (s, CO).
6

3. Results and discussion
3.1. Synthesis
Reaction of dimethyl sulfide with the 2-bromo-4׳-cyanoacetophenone in equimolar ratio gave the
compound S. The resulted S was treated with NaOH 10% to obtain the sulfur ylide. The reaction
of sulfonium salt with HgX2 (X = Cl, Brand I) and Hg(NO3)2∙H2O in [1:1] ratio yielded the
dimeric and polymeric complexes, 1-3 and 4 (scheme 2). X-ray quality crystals of compounds Y
and 1 were grown by slow evaporation from DMSO over 3 weeks. Because of the very low
solubility of these complexes in most common solvents such as chloroform, acetone, and
ethanol, DMSO was found to be a suitable solvent for the NMR spectroscopy and crystallization.
Scheme 2. (i); acetone for 15 h, (ii); 30 min, (iii) and (iv); methanol for 4 h.
3.2. Spectroscopy
1
All structures were characterized by H and 13C NMR spectroscopy and other conventional
techniques such as IR and elemental analysis. The CHNS elemental analysis of the mercury
complexes 1-4 shows a 1:1 stoichiometry between the sulfur ylide and HgX2 (X = Cl, Br, I or
NO3). Table 1 summarizes the spectroscopic data for synthesis of compounds.
7

The ν(CO) in the IR spectrum of the sulfonium salt is observed as a sharp band at
1688 cm-1, showing a higher frequency shift than the related sulfur ylide (1579 cm-1). This
absorption band, that is very sensitive to variations in bond order, is observed for complexes 1-4
at higher frequencies (1640-1661 cm-1) compared to the sulfur ylide. Also, the infrared spectrum
of complex 4 is a good indicator for detection of polymerization. The NO2 group in the infrared
spectrum has two strong peaks at 1300-1390 and 1530-1600 cm-1. These peaks were assigned to
the symmetric and asymmetric stretching vibrations of the NO2 group in the Hg(NO3)2∙H2O,
respectively. The peak of the asymmetric stretching vibration has been removed and the peak at
1384 cm-1 is related to the vibration of N-O stretching in complex 4 [31].
1
The H NMR spectrum of the sulfur ylide exhibits methinic proton signals at lower
frequencies in contrast to that of the sulfonium salt. This upfield shift is due to the vicinity of a
formal negative charge on the methinic carbon, which increase the electron density in C-H bond.
The chemical shifts of the methinic protons of complexes can be used to determine the
coordination mode of the ligands to the metal center. The 1H NMR signals for SCH group of all
complexes, due to removal of some electron density in S-C bonds, occur at higher frequencies in
comparison to those of the sulfur ylide [32]. Based on our results, the coordination of the sulfur
ylide to metal ions occurs through the ylidic carbon atom.
13
The most interesting aspect of the C NMR spectra of the complexes, due to the change
in hybridization of the ylidic carbon atom from sp2 to sp3, is the lower shielding of the ylidic
carbon atoms. The 13C chemical shifts of the CO group in all complexes were found to be around
190 ppm, relative to 180 ppm noted for the same carbon in the parent ylides, indicating a
decreased shielding of this carbon atom in mercury complexes. No coupling to (199Hg, 16.8%
abundance, I = 1/2) was observed at room temperature in 1H and 13C NMR spectra [12].
3.3. Crystal structure analysis
X-ray quality crystals of the ligand Y and complex 1 were grown by the slow evaporation from
DMSO over 3 weeks. The molecular structures of Y and 1 were determined by single-crystal
X-ray diffraction analysis. The molecular structure of these compounds is shown in figures 1
and 2, respectively. Summarized in table 2 are crystallographic data concerning data collection
and structure solution and refinement. Selected bond lengths and angles are presented in
tables S1 and S2 of Supporting Information. Compound Y was crystallized in the
8

centrosymmetric monoclinic space group P21/c. In the structure of Y, the S1-C1 bond length of
1.7127(12) Å is significantly less than that of the two S-C single bonds (S1-C10 = 1.8002(13) Å
and S1-C11 = 1.7993(12) Å). The dihedral angle between the aromatic ring and the keto group is
15.80(6)°. Weak C-H… N and C-H… O interactions link the molecules into a 2D polymer lying
in the plane. Compound 1 is crystallized in the centrosymmetric triclinic space group P-1. The
asymmetric unit consists of one Y ligand, one Hg(II) ion and two Cl- ions. A dinuclear structure
is built up around an inversion center, similar to previously reported C-coordinated Hg(II) halide
complexes of dimethyl sulfur ylides [12, 13, 16]. Each Hg(II) center is four-coordinate and
shows an sp3 hybridization, with its coordination environment, including a short terminal Hg-Cl
bond (2.386(2) Å), one Hg-C bond (2.164(7) Å), and two asymmetric bridging Hg-Cl bonds
(2.6915(15) and 2.7537(15) Å). When compared to analogous C-coordinated dinuclear Hg(II)
chloride complexes of triphenyl phosphonium ylides, the Hg-C bond distances are significantly
shorter in the sulfur ylides than the equivalent distances in the phosphonium analogs, pointing
towards a higher basicity of the sulfur ylides, as previously explained [12, 13]. The six angles
subtended by the different ligands at the Hg(II) center vary from 84.39(5)° to 142.35(16)°,
indicating a highly distorted tetrahedral coordination environment. The two Hg(II) atoms and
two bridging chlorides are perfectly coplanar, while the internuclear distance between the two
Hg(II) atoms is 4.0344(5) Å. Comparable features have been previously reported for similar
dimethyl sulfur ylides [12, 13, 16]. In the crystal packing, short π-π ring interactions are
observed between the cyanophenyl rings (centroid-centroid distances of 3.921(4) Å and
3.910(4) Å).
3.4. Evaluation of biological activities
3.4.1. Antioxidant activity. DPPH has been broadly used to test the antioxidant potential of
different compounds. The antioxidants have the ability to reduce stable radicals changing the
characteristic deep purple color (λmax = 515-517 nm) of DPPH to the yellow-colored nonradical
diphenyl-picrylhydrazine (DPPH-H) [33, 34]. Results of DPPH assay are summarized in table 3
(see also table S3 in Supporting Information). According to our results, most of the synthesized
compounds display tremendous dose-dependent (0.2-1 mg∙mL-1) antiradical activity (46.81-
70.53%) (table 3). The scavenging activity is higher when the IC50 value is low. The
effectiveness of the samples as DPPH radical scavengers ranged in the following descending
9

order: (i) ylide (IC50 = 0.16±0.01 mg∙mL-1) < (ii) [HgCl2(Y)]2 (IC50 = 0.19±0.05 mg∙mL-1) <
(iii) [HgI2(Y)]2 (IC50 = 0.52±0.01 mg∙mL-1) < (iv) [HgBr2(Y)]2 (IC50 = 0.53±0.01 mg∙mL-1) <
(v) [Hg(NO3)2(Y)]n complexes (IC50 = 0.94±0.01 mg∙mL-1). Results showed that (i) and (ii) were
compared with ascorbic acid and quercetin as standard antioxidant in radical scavenging. A
comparison between the DPPH radical scavenging activity of the synthesized compounds and
some of other ylide-based compounds studied in the literature is shown in table 4. The results
exhibited that 1 was nearly twice as active in DPPH radical scavenging abilities as those of C3,
being the strongest antioxidant complex studied by our group [35]. In addition to 1, the other
studied complexes in this work had higher antioxidant properties than those previously reported
[35]. Altogether, the compounds with sulfur ylides and their Hg(II) complexes can significantly
improve the radical scavenging activity in comparison to phosphorus ylides and their Pd(II)
complexes. Based on the IC50 values, the studied compounds could be divided into three distinct
parts (figure 3). The first part which consisted of quercetin, ascorbic acid, and Y showed low
IC50 values (0.13-0.16 mg∙mL-1). It could be pointed out that these compounds possess the high
antioxidant potential. The second part was made of 1, 2 and 3. This group which has dimeric
structure of mercury(II) halides was characterized by a moderate amount of IC50. The IC50 values
of this compound varied from 0.19 to 0.53 mg∙mL-1. The third part constituted of complex 4 and
showed high IC50 values (0.94 mg∙mL-1) (figure 3). This compound has polymeric structure of
mercury(II) nitrate.
3.4.2. Antibacterial activity. Results showed that both Gram-negative and -positive bacteria
were annihilated by the complexes (table 5). However, the complexes represented antibacterial
activity against the Gram-negative bacteria more than -positive ones, which can be attributed to
the differences in their cell wall structures in that the cell wall of Gram-positive bacteria is made
of a thick layer of peptidoglycan, comprising of linear polysaccharide chains cross-linked by
short peptides thus forming more rigid structure leading to the difficult penetration of the
compounds while in the Gram-negative bacteria, the cell wall possesses only a thinner layer of
peptidoglycan [33].
According to our results, the Hg(II)-ligand (average inhibition zone: 32 mm) and the
HgNO3 complex (average inhibition zone: 27 mm) represented a significant effect on Gram-
negative and -positive bacteria, respectively. Apparently, Escherichia coli (-) and Klebsiella
10

oxytoca(-) were the most sensitive bacteria and conversely, Listeria monocytogenes (+) was one
of the most resistant synthesized compounds. In a comparison of their antibacterial activities
with those of reference antibiotics, the complexes seem to have extraordinary inhibitory potency
against the bacteria tested. As can be seen in table 6, the antibacterial activity of Hg(II) complex
with sulfur ylide showed the significant effect against Gram-positive bacteria, especially
B. cereus and S. aureus, in comparison to the other metal complexes with different ylide ligands.
Generally, the antibacterial activity of a compound is ascribed mainly to its major components.
On the other hand, our findings suggest that the synthesized Hg(II) complexes can be considered
as potential biocides in composite materials.
3.5. Powder XRD studies
The XRD pattern of 1-3 was considered in a domain of 10 to 80 degrees. This pattern indicates
the crystalline nature for the complexes. Peak width (FWHM) was investigated. The prominent
peaks of the diffraction pattern were indexed (graph 1). The obtained data are collected in
table 7. The crystallite size D of the complexes was calculated using the Debye-Sherrer formula
D = Kλ/(ßCosθ), with λ being the X-ray wavelength (λ = 0.154 nm), K is the Scherrer constant
(0.9), ß the peak width of half-maximum (FWHM) and θ is the Bragg diffraction angle. The
interplanar distance was calculated via the Bragg equation: dhkl = λ/(2sin θ), (λ : Cu radiation
(0.154184 nm).
11

3500
3000
2500
2000
1500
1000
500
1
2
3
0
0
20
40
60
80
100
̊2 Theta
Graph 1. XRD graph of complexes 1-3.
4. Conclusion
This study portrays the synthesis and characterization of dimeric and polymeric Hg(II)
complexes of sulfur ylide. The structure of the compounds was determined successfully by IR,
13
1H, C NMR spectroscopic techniques and elemental analysis. Based on the physicochemical
and spectroscopic data, we propose a monodentate C-coordinate of the sulfur ylide to the metal,
which is further confirmed by the X-ray crystal structure of 1. In this complex, the related ligand
is coordinated to one mercury atom through the ylidic carbon atom. In the following, a
symmetric halide-bridged dimeric structure to the Hg(II) chloride is formed. Furthermore, our
results revealed the antioxidant potency and antibacterial activity of the complexes on the growth
of both Gram-positive and -negative bacteria. The XRD pattern indicated crystalline nature
for 1-3.
Supplementary material
CCDC 1559666-1572297 contain the supplementary crystallographic data for Y and 1. These
data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: +44-
1223-336033; or E-mail: deposit@ccdc.cam.ac.uk).
12

Acknowledgements
We are grateful to Bu-Ali Sina University for financial support. KVH thanks the Hercules
Foundation (project AUGE/11/029 "3D-SPACE: 3D Structural Platform Aiming for Chemical
Excellence") for funding and the Research Foundation - Flanders (FWO) (project 1.5.216.15N)
for financial support.
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15

Figure 1. ORTEP view of the X-ray crystal structure of Y with atom labeling scheme. H atoms
are omitted for clarity.
Figure 2. ORTEP view of the X-ray crystal structure of 1, with atom labeling scheme. H atoms
are omitted for clarity.
16

Group II
Group III
Group I
Figure 3. Dendrogram obtained from the cluster analysis of the synthesized compounds and
antioxidant standards based on the antioxidant activity (IC50 value).
17

Table 1. Spectroscopic data for compounds S, Y and 1-4.
Compound
IR; ν(CO) cm-1
1H NMR; δ(SCH) ppm
13C NMR; δ(SCH) ppm
13C NMR; δ(CO) ppm
S
Y
1
1688
1579
1655
1653
1640
1661
5.64
4.31
54.92
53.25
195.88
180.33
5.49
64.58
190.56
2
5.43
64.52
189.58
3
5.32
64.23
188.39
4
5.51 and 5.97
60.36 and 67.55
192.10 and 194.57
18

Table 2. Crystallographic data for Y and 1.
Y
1
Empirical formula
Formula weight/gmol-1
C11H11NOS
C22H22Cl4Hg2N2O2S2
953.52
205.27
T/K
130.01 (10)
100.0 (1)
Radiation/Å
CuKα (λ = 1.54184)
CuKα (λ = 1.54184)
Crystal system
Monoclinic
Triclinic
P-1
Space group
P21/c
a/Å
5.38363(11)
6.9757(6)
7.7187(5)
14.0471(10)
77.598(6)
87.630(7)
b/Å
8.15920(18)
c/Å
22.8755(5)
α/°
90
β/°
91.4503(19)
γ/°
90
66.785(7)
Volume/Å 3
1004.51(4)
678.09(10)
Z
4
1
ρcalc /gcm-3
1.357
2.335
μ/mm-1
2.566
25.284
F (000)
432.0
444.0
Crystal size/mm3
2Θ range for data collection/°
Index ranges
0.337 × 0.252 × 0.056
7.732 to 153.746
0.127 × 0.056 × 0.044
6.45 to 150.404
-6 ≤ h ≤ 5, -10 ≤ k ≤ 10, -28 ≤ l ≤ 28
8244
-8 ≤ h ≤ 8, -9 ≤ k ≤ 9, -17 ≤ l ≤ 17
12920
Reflections collected
Independent reflections
Data / restraints / parameters
Final R indices [Io > 2σ (Io)]
Final R indexes [all data]
Largest diff. peak/hole /e Å-3
Goodness-of-fit on F2
2110 [Rint = 0.0202, R sigma = 0.0170]
2110 / 0 / 129
2752 [Rint = 0.0693, R sigma = 0.0435]
2752 / 0 / 156
R1 = 0.0296, wR2 = 0.0821
R1 = 0.0303, wR2 = 0.0832
0.30/-0.33
R1 = 0.0396, wR2 = 0.0987
R1 = 0.0432, wR2 = 0.1013
1.32/-1.53
1.042
1.062
19

Table 3. Scavenging activity (%) and IC50 value of [HgX2(Y)]2 (Y:
(Me)2SC(H)C(O)C6H4-p-CN, X: Cl (1), Br (2), I (3), NO3 (4)) at different
concentrations (mg∙mL-1), quercetin and ascorbic acid as antioxidant standards.
Concentration (mg∙mL-1)
IC50 Value
Sample
Average
(mg∙mL-1)
0.2
0.4
0.6
0.8
1
61.20±1.65b 65.47±0.70b 70.83±1.15b 75.04±1.37b 80.12±0.54a
53.50±0.73c 48.26±0.14e 64.80±1.15c 68.33±0.64c 71.40±0.73b
54.73±1.01c 57.80±0.79d 56.38±0.76e 56.57±0.25e 57.28±0.25c
61.01±1.22b 60.82±0.45c 57.60±0.59d 60.39±0.88d 59.27±0.36c
45.79±0.65d 45.89±0.31f 43.06±0.63f 46.44±0.57f 53.40±0.49d
71.47±1.00a 73.75±0.99a 77.07±1.51a 78.86±1.53a 80.89±1.09a
70.53
61.25
56.56
59.81
46.92
76.41
0.16±0.01c
0.19±0.05c
0.52±0.01b
0.53±0.01b
0.94±0.01a
0.14±0.01c
Y
1
2
3
4
Ascorbic
acid
Quercetin
76.11±0.69a 81.13±1.01a 86.85±1.81 a 88.13±0.92a 91.85±1.32a
84.81
0.13±0.01c
a
Experiment was performed in triplicate and expressed as mean ± SD. Values along
each column with different superscripts are significantly different (P< 0.05).
20

Table 4. Comparison of DPPH radical scavenging activity (%) of the studied
compounds with the other ylide derivates as reported in literature.
Average percentage of
Compound
Reference
scavenging activity (%)
61.25
56.56
59.81
46.92
30.55
32.86
35.53
31.67
This work
This work
This work
This work
[35]
1
2
3
4
C1
C2
C3
C4
[35]
[35]
[35]
Note: [(dppe)Pd(Ph2PCH2PPh2C(H)C(O)PhX)] (OSO2CF3)2 (X = Br (C1), Cl (C2),
NO2(C3), OCH3(C4))
21

Table 5. Antibacterial activity of [HgX2(Y)]2 (Y: (Me)2SC(H)C(O)C6H4-p-CN, X: Cl (1), Br (2), I (3),
NO3 (4)), antibiotics (positive controls) and DMSO (negative control) against the studied bacterial
strains.
Inhibition zone (mm)
Sample
S.
K.
S.
L.
B.
B.
cereus
S.
aureus
E.coli
typhimurium oxytoca dysenteriae monocytogenes subtilis
15±0.43
13±0.56
17±0.51
16±0.82
18±0.37
18±0.14
12±0.10
20±0.18
28±0.59
30±0.63
30±0.22
32±0.72
12±0.12
13±0.12
19±0.17
25±0.35
Na
20±0.78
15±0.84
21±0.18
20±0.24
26±0.24
18±0.14
14±0.17
22±0.22
30±0.22
Na
29±0.35
18±0.29
12±0.17
7±0.25
30±1.08
16±0.16
14±0.11
21±0.19
24±0.31
Na
44±0.65
20±0.17
31±0.35
36±0.33
20±0.66
10±0.12
12±0.08
26±0.45
28±0.26
Na
30±0.26 14±0.24 38±0.96
15±0.29 25±0.12 26±0.24
20±0.73 30±0.27 14±0.75
21±1.00 28±0.51 7±0.14
21±0.22 32±0.28 40±0.49
13±0.12 14±0.13 13±0.10
14±0.09 12±0.11 16±0.13
18±0.16 18±0.20 13±0.17
23±0.22 25±0.17 26±0.21
Y
1
2
3
4
Penicillin
Ampicillin
Vancomycine 22±0.22
Tetracycline
DMSO
28±0.54
Na
Na
Na
Na
Experiment was performed in triplicate and expressed as mean ± SD.
22

Table 6. Comparison of the average inhibition zone resulted from the synthesized compounds
with the other metal-ylide complexes as reported in literature.
Inhibition zone (mm)
Microorganism
B. cereus
S. aureus
E. coli
Hg(II) complex of sulfurylide (this work)
Hg(II) complex of phosphoniumylide [36]
Hg(II) complex of sulfurylide [37]
28.75
44
21.75
30
16
-
19.66
-
24
20.33
-
Pd(II) complex of phosphine ylide [38]
Cu(I) complex of phosphine ylide [39]
15.25
17.25
12.25
14.75
23

Table 7. X-ray diffraction (XRD) data.
Peak width (degree)
(FWHM)
Entry
Complexes
2θ
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
12.67
11.97
11.89
12.94
12.3
0.196
0.147
0.147
0.147
0.196
0.344
0.246
0.196
0.295
0.246
0.196
0.196
0.344
0.246
0.196
0.393
0.196
0.344
0.295
0.196
0.246
0.196
0.246
0.246
1
2
3
4
5
6
7
8
13.82
26.46
28.69
25.91
28.12
28.69
28.42
31.55
32.01
31.48
37.30
37.01
37.04
39.29
39.67
39.42
47.29
46.40
46.34
24

Graphical abstract
25