Synthesis and characterization of novel simultaneous C and O-coordinated and nitrate-bridged complexes of silver(i) with carbonyl-stabilized sulfonium ylides and their antibacterial activities

Article abstract of DOI:10.1039/c2dt31902k

Reaction of sulfonium ylides (Me)₂SCHC(O)C₆H ₄R (R = H; m-NO₂; p-NO₂; p-OMe; p-Me and p-Br) with AgNO₃ in dichloromethane leads to various compounds. Single crystal X-ray diffraction analysis reveals that the adducts take 3 forms: (i) two-dimensional polymer, [AgNO₃(Me₂SCHC(O)C ₆H₅)]_n (1), with nitrate bridges in which each nitrate coordinates to three silver atoms through two oxygen atoms and two Me₂SCHC(O)C₆H₅ ligands coordinate to silver centers through carbon atoms; (ii) cationic binuclear, [Ag(Me ₂SCHC(O)C₆H₄-m-NO₂) ₂]₂(NO₃)₂·2H₂O (2), in which Me₂SCHC(O)C₆H₄-m-NO₂ ligands simultaneously coordinate through both carbon and oxygen atoms with nitrate as a counter ion, and (iii) cationic mononuclear and anionic binuclear, [Ag(Me₂SCHC(O)C₆H₄-p-NO₂) ₂]₂[{AgNO₃(μ-NO₃) (Me ₂SCHC(O)C₆H₄-p-NO₂)} ₂]·2CH₃OH (3), in which nitrate groups act as bridging as well as terminal ligands, and Me₂SCHC(O)C ₆H₄-p-NO₂ ligands display C-coordination. Characterization of the obtained compounds was also performed by infrared, ¹H- and ¹³C-NMR spectroscopy and analytical data indicated a 1:2 stoichiometry between the silver(i) nitrate and ylide p-OMe (4) and 1:1 for ylides p-Me (5) and p-Br (6). In addition, the antibacterial effects of DMSO-solutions of complexes 1-6 were evaluated by the agar disc diffusion method against three Gram positive and three Gram negative bacteria. All complexes displayed antibacterial activity against these bacteria, with high levels of inhibitory potency exhibited against the Gram negative species.

Full text of DOI:10.1039/c2dt31902k

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Synthesis and characterization of novel simultaneous
C and O-coordinated and nitrate-bridged complexes of
silver(I) with carbonyl-stabilized sulfonium ylides and
their antibacterial activities†
Cite this: Dalton Trans., 2013, 42, 2520
Seyyed Javad Sabounchei,*a Fateme Akhlaghi Bagherjeri,a Zeinab Mozafari,a
Colette Boskovic,b Robert W. Gable,b Roya Karamianc and Mostafa Asadbegyc
Reaction of sulfonium ylides (Me)2SCHC(O)C6H4R (R = H; m-NO2; p-NO2; p-OMe; p-Me and p-Br) with
AgNO3 in dichloromethane leads to various compounds. Single crystal X-ray diffraction analysis reveals
that the adducts take 3 forms: (i) two-dimensional polymer, [AgNO3(Me2SCHC(O)C6H5)]n (1), with nitrate
bridges in which each nitrate coordinates to three silver atoms through two oxygen atoms and two
Me2SCHC(O)C6H5 ligands coordinate to silver centers through carbon atoms; (ii) cationic binuclear,
[Ag(Me2SCHC(O)C6H4-m-NO2)2]2(NO3)2·2H2O (2), in which Me2SCHC(O)C6H4-m-NO2 ligands simul-
taneously coordinate through both carbon and oxygen atoms with nitrate as a counter ion, and (iii) cat-
ionic mononuclear and anionic binuclear, [Ag(Me2SCHC(O)C6H4-p-NO2)2]2[{AgNO3(μ-NO3) (Me2SCHC(O)-
C6H4-p-NO2)}2]·2CH3OH (3), in which nitrate groups act as bridging as well as terminal ligands, and
Me2SCHC(O)C6H4-p-NO2 ligands display C-coordination. Characterization of the obtained compounds
was also performed by infrared, 1H- and 13C-NMR spectroscopy and analytical data indicated a 1 : 2 stoi-
chiometry between the silver(I) nitrate and ylide p-OMe (4) and 1 : 1 for ylides p-Me (5) and p-Br (6). In
addition, the antibacterial effects of DMSO-solutions of complexes 1–6 were evaluated by the agar disc
diffusion method against three Gram positive and three Gram negative bacteria. All complexes displayed
antibacterial activity against these bacteria, with high levels of inhibitory potency exhibited against the
Gram negative species.
Received 20th August 2012,
Accepted 12th November 2012
DOI: 10.1039/c2dt31902k
www.rsc.org/dalton
Introduction
In contrast to the numerous reported examples of silver(I) com-
plexes of phosphonium ylide, sulfonium analogs have not
been observed so far. Only one type of silver(I) complex for
α-keto stabilized phosphorus ylides is known, [Ag(Y)2]X,
with Y = Ph3PCHCOR (R = aryl or alkyl) and X = NO3, ClO4
or OTF.1–4 The potential richness in terms of coordinative
versatility of sulfur–ylides (Scheme 1), and the use of these
compounds in organic5–8 and organometallic reactions, led us
to the present study. Herein we report the synthesis of various
stable silver(I) complexes, which are the first with carbonyl-
Scheme 1 The canonical forms of (Me)2SCHC(O)C6H4R (R = H; m-NO2; p-NO2;
p-OMe; p-Me and p-Br) and their various coordination modes to a silver(I)
center.
aFaculty of Chemistry, Bu-Ali Sina University, Hamedan, 65174, Iran.
E-mail: jsabounchei@yahoo.co.uk; Fax: +98 8118273231; Tel: +98 8118272072
bSchool of Chemistry, University of Melbourne, Victoria, 3010, Australia
cDepartment of Biology, Faculty of Science, Bu-Ali Sina University, Hamedan, 65174,
Iran
stabilized sulfur ylides and the single crystal X-ray structures
of examples of three structural types. The development of
materials with the ability to inhibit bacterial growth have been
†Electronic supplementary information (ESI) available. CCDC 881007, 881006
and 865650. For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/c2dt31902k
2520 | Dalton Trans., 2013, 42, 2520–2529
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of great interest in recent years due to their potential use in noted for the same carbon in the parent ylides, indicating
everyday products like paints, kitchenware, school and hospi- decreased shielding of this carbon atom in silver complexes.
tal utensils, etc. Nowadays, microorganisms resistant to mul- Interestingly, although ylide Me2SCHC(O)C6H4-m-NO2 coordi-
tiple antimicrobial agents are serious problems worldwide in nates to complex 2 through carbon and oxygen simultaneously,
the fight against infectious diseases, increasing morbidity and but the infrared and NMR spectra show only C-coordination. It
mortality with an overall increase in health care costs.9–11 For should arise from an extremely poor band between oxygen and
these reasons, there is an urgent need to develop novel anti- silver centers that can also be confirmed with the related bond
microbial agents with difficult mechanisms of action aimed at a length in the X-ray crystal structure. No coupling to Ag (109Ag,
better understanding of the antimicrobial resistance. It is well 48.18% abundance, I = 1/2) was observed at room temperature
known that silver ions and silver-based compounds are highly in 1H and 13C NMR spectra. It is possible that a fast equili-
toxic to microorganisms.12,13 Various forms of silver and its brium between complexes and the free ylides is responsible for
compounds have been investigated in the past few decades the failure to observe either NMR couplings or the presence of
due to the antimicrobial activity of silver ions, and there is an two diastereoisomers.1
increased interest in the potential use of silver(I) as a thera-
X-ray crystallography
peutic agent for different antimicrobial applications.14–20 It is
well established that only silver in its ionic or complex forms The molecular structures of 1, 2 and 3 were determined
has antimicrobial activity, while elemental silver, even in the through single crystal X-ray diffraction methods. The molecu-
so-called “nanocrystalline” state is not.21 Silver containing lar drawing of complexes 1, 2 and 3 are shown in Fig. 1–3.
compounds are attractive because of the fact that in the range Crystallographic data and parameters concerning data collec-
of the applicable concentrations, silver ions have limited tion and structure solution and refinement are summarized in
toxicity because there is some research that has shown that Table 1 and selected bond distances and angles are presented
although not
a large amount, the ions do have some in Tables 2 and 3, respectively. Crystallographic data for all of
toxicity.22–24 In the present work, a series of silver(I) complexes the structures in this paper can be found in the ESI.†
were prepared and characterized and their antibacterial activi-
ties were evaluated (Scheme 2).
Compound 1 is a polymer and one formula unit, devoid of
crystallographic symmetry, comprising the asymmetric unit
of the structure (Fig. 1a and 1b). The silver(I) center in the
monomer is four-coordinate with sp3 hybridization. This
environment involves one nitrate Ag–O4 bond (connects the
monomers together and comprises the polymer), one Ag–C
bond and two asymmetric bridging Ag–O bonds of two
Results and discussion
Spectroscopy
In the infrared spectra the carbonyl stretch that is sensitive to different nitrates. The angles subtended by the ligands at the
complexation, occurs at about 1551–1580 cm−1 for the parent silver(I) center vary from 83.46(7)° to 158.88(9)° indicating a
ylides, as in the case of other resonance stabilized ylides.25 very distorted tetrahedral coordination geometry. The unsym-
Coordination of the ylide through carbon causes an increase metrical nitrate coordination is reflected in its geometry,
in ν(CO), while for O-coordination a decrease of ν(CO) is with N1–O4 longer than N1–O2 and O4–N1–O2 reduced to
expected. The infrared absorption bands observed for all our 118.8(2)°. Vicente et al.1 reported a quasi-linear structure for the
complexes at about 1661–1686 cm−1 suggest coordination of phosphorus analog with the same substituent in which nitrate
the ylide through the carbon atom. The infrared data were ions are loosely associated with the metal center. The Ag–Cα
inconclusive in this project because of overlap of ν(NO) and (ylide), CvO and CO–Cα bond lengths (Table 2) are very close
ν(NO2) bonds of the NO3− group with the ylide bonds.1
to the sulfonium analog, complex 1, within experimental error.
Although two diastereoisomers (RR (1) and SS/RS (2 and 3)) This similitude is worthy of note, taken into account that
are possible for each complex (because the methine carbons sulfur ylides are more basic than phosphorus ylides, provided
are chiral), 1H NMR spectroscopy does not distinguish that the two have the same substituents.27
between them at room temperature, even at 400 MHz and
The configuration at the chiral carbon atoms in compound
the methine resonances are intermediate between these 2 are RS for Ag1 and SS for Ag2. The silver atoms display
diastereoisomers.1–3 The 1H NMR signals for the SCH group of two different coordination geometries one of which is two-
complexes 1–6 are shifted downfield compared to those of the coordinate and quasi-linear and the other is three-coordinate,
free ylides, as a consequence of the inductive effect of the actually it can be said there are two quasi linear complexes
metal center. The appearance of single signals for the SCH one of which coordinates to the oxygen of the ligand of
1
group in H NMR at ambient temperature indicates the pres- the other complex. This bond is weak (2.710 Å) and it causes
ence of only one geometrical isomer for all complexes as a slight increase in length of the C24–O4 bond rather than
expected for C-coordination. It must be noted that O-coordi- the other carbonyl bond length (Table 2). Two nitrate
nation of the ylide leads to the formation of cis and trans ions appear as counter ions and there is no Ag–ONO2
isomers giving rise to two different signals in 1H NMR spec- interactions.
trum.26 The 13C chemical shifts of the carbonyl carbon atoms
There are two cation (+1) and one anion (−2) parts in the
in complexes 1–6 are around 187 ppm, relative to ∼182 ppm unit cell of complex 3 which are all silver(I)–ylide complexes.
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Scheme 2 Different structures of complexes 1–6 in dichloromethane as solvent.
The configuration at the chiral carbon atoms in the cation and similar to analogous phosphorus ylide complexes reported to
anion are RS and SS, respectively. In the anionic part, one date.1–4 The conformation about the molecular axis C1–C11 is
formula unit comprises the asymmetric unit of the structure almost eclipsed (Fig. 3). The coordination geometry at silver is
and silver atom being related by the inversion centre in the tri- essentially linear, although bond lengths and angles at the
ˉ
clinic space group P1 to form the whole molecule. The array silver are slightly distorted (Tables 2 and 3).
about the silver(I) center is similar to complex 1 but herein
There are no phosphorus analogs with the same substitu-
nitrate coordinated through O10, cf. O4 in complex 1, is a ents for complexes 2 and 3 to compare the corresponding
terminal ligand. The configuration of the cationic part is quite bond length and angle values.
2522 | Dalton Trans., 2013, 42, 2520–2529
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Fig. 2 ORTEP view of the X-ray crystal structure of 2. The H atoms, tow nitrate
counter ions and two water molecules have been omitted and the phenyl rings
have been shown as wire form for clarity.
Fig. 1 ORTEP view of the X-ray crystal structure of 1. (a) Asymmetric unit and
(b) polymeric chain. The H atoms have been omitted for clarity. Symmetry code:
a3/2 − X, 1/2 + Y, +Z; b3/2 − X, −1/2 + Y, +Z.
Although, we could not obtain good qualified single crystals to
determine the true structures 4–6 by X-ray crystallography, never-
theless we investigated the spectroscopy and analytical data to
suggest the possible structures. Infrared, 1H- and 13C-NMR spectra
for complexes 4–6 are quite similar to complexes 1–3 so the
analytical data helped us to predict possible structures for com-
plexes 4–6. Analytical data shows the stoichiometry between the
silver(I) nitrate and ylide p-OMe (4) is 1 : 2 that is similar to
complex 2, a cationic binuclear, and 1 : 1 for ylides p-Me (5) and p-
Br (6) which is similar to complex 1, a two-dimensional polymer.
Fig. 3 ORTEP view of the X-ray crystal structure of 3. The H atoms and two
methanol molecules (solvent) have been omitted and the phenyl rings have
been shown as wire form for clarity. Symmetry code: a1 − X, −Y, 1 − Z.
are shown in Table 11. The new complexes and their free
ligands all displayed antibacterial activity against all bacteria
tested especially on Gram negative ones. A comparative study
of the growth inhibition zone values of ligands and its com-
plexes indicate that complexes exhibit higher antibacterial
activity than the free ligands. However, the presence of the
Antibacterial activity
Results from the antibacterial assessment of the samples are
presented in Tables 4–10 and positive and negative controls
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Table 1 Crystal data and refinement details for 1, 2 and 3
1
2
3
Identification code
Formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
fa-assg
10H12AgNO4S
350.14
130(2)
1.54184
fa-agmGau
C20H24N3O10S2Ag
638.41
130(2)
1.54184
Triclinic
ˉ
P1
fa-asng
C62H74N10O32S6Ag4
2095.15
130(2)
0.71073
Triclinic
ˉ
P1
C
Orthorhombic
Pbca
Unit cell dimensions
a = 8.45746(19)
b = 9.22142(17)
c = 30.5647(7)
α
10.6373(4)
11.2057(3)
23.4336(6)
80.762(2)
11.7239(4)
12.3813(3)
15.3188(4)
70.686(3)
β
83.424(3)
68.015(3)
γ
71.797(3)
2612.88(14)
4, 1.623
8.192
1296
88.073(2)
1935.54(10)
1, 1.797
1.252
Volume (Å3)
2383.73(9)
8, 1.951
15.259
Z, calculated density (Mg m−3
)
Absorption coefficient (mm−1
F(000)
)
1392
1056.0
Crystal size (mm)
θ range for data collection (°)
Limiting indices
0.29 × 0.10 × 0.08
2.88–76.80
−10 ≤ h ≤ 10
−9 ≤ k ≤ 11
−38 ≤ l ≤ 38
22 299
0.36 × 0.16 × 0.06
3.83–77.17
−13 ≤ h ≤ 12
−13 ≤ k ≤ 14
−28 ≤ l ≤ 29
26 669
0.22 × 0.10 × 0.05
2.85–30.06
−16 ≤ h ≤ 15
−16 ≤ k ≤ 16
−21 ≤ l ≤ 21
21 179
Reflections collected/unique
2518 [R(int) = 0.0401]
99.97%
10 925 [R(int) = 0.0325]
99.91%
10 020 [R(int) = 0.0299]
99.88%
Completeness
Absorption correction
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
Gaussian
Gaussian
Gaussian
Full-matrix least-squares on F2
2518/0/156
1.095
Full-matrix least-squares on F2
10 925/62/659
1.064
Full-matrix least-squares on F2
10 020/12/524
1.039
R1 = 0.0278, wR2 = 0.0663
R1 = 0.0310, wR2 = 0.0688
0.670 and −0.81
R1 = 0.0540, wR2 = 0.1587
R1 = 0.0609, wR2 = 0.1665
2.77 and −1.84
R1 = 0.0356, wR2 = 0.0705
R1 = 0.0532, wR2 = 0.0791
0.68 and −0.66
Largest diff. peak and hole (e Å3)
attributed mainly to their major components. However, today
it is well known that the synergistic or antagonistic effect of
one compound present in a minor percentage of a mixture has
to be considered.28 When antimicrobial activities of the tested
samples were compared with some reference antibiotics, the
inhibitory potency of the tested ligands and chiefly complexes
was found to be remarkable (Tables 4–11). Although all bac-
teria tested are resistant to penicillin and E. coli to gentamicin,
the antibacterial effects of all ligands and their complexes
were higher than those of antibiotics on these bacteria. The
complexes showed more activity against some bacteria under
identical experimental conditions. This would suggest that the
structure of the complexes may reduce the polarity of the
metal ion mainly. In addition, silver(I) ions reportedly adhere
to the negatively charged bacteria cell walls and change the
cell wall permeability. This action coupled with protein de-
naturation induces cell lyses and death.29 The antimicrobial
activity of silver ion is also related to its ability to modify DNA
replication mechanisms as well as to cause abnormalities in
the size, cytoplasmic contents, cell membrane, and outer cell
layers of sensitive cells.30 Overall the present study revealed
Gram negative bacteria to be more susceptible to the antibac-
Table 2 Selected bond lengths (Å) for 1, 2 and 3 and comparison of complex
1 with triphenylphosphonium analog
1
[1]
2
3
Ag1–C1 2.198(3) 2.219(9) Ag1–C1 2.192(5) Ag1–C1
2.215(2)
Ag1–O4a 2.303(2) 2.751(10) Ag1–C10 2.202(5) Ag1–C11 2.206(3)
Ag1–O2 2.590(2) 2.77(1)
Ag2–C21 2.177(5) Ag2–C21 2.233(3)
C1–C2
C2–O1
C1–S1
1.454(4) 1.471(13) Ag2–C31 2.177(5) Ag2–O14 2.668(3)
1.239(3) 2.233(16) C21–C24 1.445(8) Ag2–O14a 2.414(2)
1.765(3)
C31–C34 1.464(6) Ag2–O10 2.359(2)
C1–C11 1.447(7) C1–C2 1.448(3)
O4–Ag1b 2.302(2)
N1–O2
N1–O3
N1–O4
1.256(3)
1.234(3)
C10–C13 1.443(7) C11–C12 1.449(4)
C34–O1 1.224(6) C21–C22 1.501(5)
1.267(3) 1.269(20) C24–O4 1.249(6) C22–O7
C13–O10 1.245(7) C12–O4
1.240(3)
1.236(3)
1.234(3)
1.759(3)
1.758(3)
1.256(3)
1.244(3)
1.259(3)
1.208(3)
1.234(3)
C11–O7 1.243(6) C2–O1
C21–S3
C31–S4
C10–S2
C1–S1
1.760(5) C21–S3
1.768(5) C1–S1
1.767(5) N4–O10
1.766(5) N4–O12
N5–O14
N5–O15
N5–O13
See Fig. 1–3 for the atom numbering. a3/2 − X, 1/2 + Y, +Z; b3/2 − X,
−1/2 + Y, +Z (1); a1 − X, −Y, 1 − Z (3)
different coordination modes does not exert much effect on terial effects of silver(I) complexes than Gram positives, pre-
the antibacterial activity of the tested complexes and almost all sumably due to their thinner wall, which may allow more
complexes exhibit equal antibacterial activity (Tables 5–10). rapid absorption of the ions into the cell.31,32 The above
Generally, antibacterial activities of the compounds are results indicate that the studied complexes may be used in the
2524 | Dalton Trans., 2013, 42, 2520–2529
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Table 3 Selected bond angles (°) for 1, 2 and 3
1
2
3
O4a–Ag1–O2
O4a–Ag1–C1
C1–Ag1–O2
Ag1–O2–N1
O3–N1–O2
O3–N1–O4
O4–N1–O2
S1–C1–Ag1
O1–C2–C1
C2–C1–Ag1
N1–O4–Ag1b
83.46(7)
C1–Ag1–C10
C11–C1–Ag1–
C13–C10–Ag1
S1–C1–Ag1
S2–C10–Ag1
O7–C11–C1
O10–C13–C10
C21–Ag2–C31
C24–C21–Ag2
C34–C31–Ag2
S3–C21–Ag2
S4–C31–Ag2
O4–C24–C21
O1–C34–C31
168.19(19)
102.2(3)
104.1(3)
111.0(2)
109.5(2)
122.1(4)
122.6(5)
167.05(18)
99.2(3)
107.0(3)
113.2(2)
106.3(2)
123.9(4)
123.4(5)
C1–Ag1–C11
C2–C1–Ag1
C12–C11–Ag1
S1–C1–Ag1
S2–C11–Ag1
O14–Ag2–O
C21–Ag2–O10
C21–Ag2–O14
C21–Ag2–O14a
O14a–Ag2–O14
N4–O10–Ag2
N5–O15–Ag2
S3–C20–Ag2
C21–C20–Ag2
166.14(9)
99.95(16)
99.61(16)
106.22(12)
112.06(13)
106.76(10)
142.08(9)
103.74(9)
133.70(9)
69.54(11)
109.7(3)
158.88(9)
113.00(8)
116.60(16)
120.8(2)
120.4(2)
118.8(2)
108.50(12)
123.0(2)
107.18(17)
111.84(16)
117.9(3)
106.72(18)
105.2(3)
Table 4 Antibacterial activity of free ligands 1–6
Inhibition zone (mm)
Compounds
Concentration
P. vulgaris (−)
E. coli (−)
B. cereus (+)
S. aureus (+)
B. megaterium (+)
S. marcescens (−)
Ligand 1
1 (mg ml−1
)
9
7
Na
0.22a
0.14b
7
Na
Na
0.18
7
Na
Na
0.00
0.12
0.15
0.15
0.15
0.18
8
Na
Na
0.00
9
7
Na
0.12a
0.28b
10 0.24a
8
Na
0.1 (mg ml−1
0.01 (mg ml−1
)
0.14b
)
)
)
)
)
Ligand 2
Ligand 3
Ligand 4
Ligand 5
Ligand 6
1 (mg ml−1
0.1 (mg ml−1
0.01 (mg ml−1
)
8
7
Na
0.24a
0.18b
10 0.15a
7
Na
8
Na
Na
7
Na
Na
0.10
8
Na
Na
0.00
0.22
11 0.24a
)
0.14b
9
0.14b
Na
1 (mg ml−1
0.1 (mg ml−1
0.01 (mg ml−1
)
9
8
Na
0.16a
0.15b
7
Na
Na
0.26
8
Na
Na
9
7
Na
0.00a
0.24b
7
Na
Na
8
7
0.24a
0.18b
)
Na
1 (mg ml−1
0.1 (mg ml−1
0.01 (mg ml−1
)
10 0.15a
8
Na
8
Na
Na
0.26
7
Na
Na
7
Na
Na
0.33
0.00
0.00
Na
Na
Na
11 0.24a
)
0.33b
9
7
0.18b
0.18c
1 (mg ml−1
0.1 (mg ml−1
0.01 (mg ml−1
)
8
Na
Na
0.16
9
7
Na
0.33a
0.00b
8
Na
Na
7
Na
Na
9
8
Na
0.33a
0.26b
9
7
0.24a
0.18b
)
Na
1(mg ml−1
0.1(mg ml−1
0.01(mg ml−1
)
9
8
7
0.28a
0.14b
0.18c
8
7
Na
0.45a
0.10b
7
Na
Na
8
Na
Na
8
7
Na
0.33a
0.14b
10 0.12a
)
9
0.36b
)
Na
Experiment was performed in triplicate and expressed as mean SD. Values with different superscripts within each column (for each bacterium
in different concentrations) are significantly different (P < 0.05). Na: Not active.
treatment of diseases caused by the bacteria tested. Further Stuart SMPI apparatus. Elemental analysis for C, H and N were
studies are needed to evaluate the in vivo potential of these performed using a Perkin-Elmer 2400 series analyzer. Fourier
compounds in animal models.
transform infrared spectra were recorded on a Shimadzu
435-U-04 spectrophotometer and samples were prepared as
KBr pellets.
Experimental
All solvents were reagent grade and used without further puri-
fication. NMR spectra were obtained on 400 MHz Varian
Preparation of ligands
MR400 and 90 MHz Jeol spectrometers in CDCl3 and DMSO-d6 The synthesis and infrared, 1H and 13C NMR spectroscopic
as the solvent. Chemical shifts (δ) are reported relative to characterization of all ligands except the new ylide, Me2SCHC-
internal TMS (1H and 13C). Melting points were measured on a (O)C6H4-m-NO2, have been reported previously33–35 and ESI.†
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Table 5 Antibacterial activity of complex 1
Table 8 Antibacterial activity of complex 4
Inhibition zone (mm)
Inhibition zone (mm)
Concentration
Concentration
Concentration
(0.01 mg ml−1
Concentration
Concentration
Concentration
(0.01 mg ml−1
)
Microorganism
(1 mg ml−1
)
(0.1 mg ml−1
10 0.14b
)
)
Microorganism
(1 mg ml−1
)
(0.1 mg ml−1
)
P. vulgaris (−)
E. coli (−)
B. cereus (+)
S. aureus (+)
B. megaterium (+)
S. marcescens (−)
12 0.22a
11 0.34a
12 0.24a
11 0.18a
10 0.16a
13 0.18a
8
0.16c
P. vulgaris (−)
E. coli (−)
B. cereus (+)
S. aureus (+)
B. megaterium (+)
12 0.43a
12 0.33a
10 0.16a
10 0.18a
10 0.16b
8
8
7
9
0.16c
0.18c
0.11c
0.14c
8
0.12b
Na
7
8
7
8
8
9
0.18b
0.12b
10 0.18b
10 0.24b
0.14c
0.22c
0.12c
0.00c
10 0.22b
Na
9
0.28b
9
0.24a
Na
9
11 0.33b
S. marcescens (−) 14 0.34a
11b 0.22b
0.18c
Experiment was performed in triplicate and expressed as mean SD. Experiment was performed in triplicate and expressed as mean SD.
Values with different superscripts within each column (for each Values with different superscripts within each column (for each
bacterium in different concentrations) are significantly different bacterium in different concentrations) are significantly different
(P < 0.05). Na: Not active.
(P < 0.05). Na: Not active.
Table 6 Antibacterial activity of complex 2
Table 9 Antibacterial activity of complex 5
Inhibition zone (mm)
Inhibition zone (mm)
Concentration
Concentration
(0.1 mg ml−1
Concentration
(0.01 mg ml−1
)
Microorganism
(1 mg ml−1
)
)
Concentration
Concentration
Concentration
(0.01 mg ml−1
)
Microorganism
(1 mg ml−1
)
(0.1 mg ml−1
)
P. vulgaris (−)
E. coli (−)
B. cereus (+)
S. aureus (+)
12 0.22a
13 0.34a
10 0.24a
11 0.18a
9
0.14b
8
0.16c
10 0.22b
10 0.18b
Na
7
8
P. vulgaris (−)
E. coli (−)
B. cereus (+)
S. aureus (+)
12 0.22a
12 0.28a
10 0.12a
11 0.17a
10 0.38b
8
0.12c
0.14c
0.22c
8
7
0.15b
0.00b
Na
Na
9
Na
9
9
7
0.24b
0.12b
B. megaterium (+) 10 0.16a
S. marcescens (−) 14 0.18a
Na
8
10 0.18b
0.22c
0.14c
11 0.33b
0.00c
B. megaterium (+) 12 0.33a
S. marcescens (−) 12 0.28a
9
0.24b
10 0.33b
Experiment was performed in triplicate and expressed as mean SD.
Values with different superscripts within each column (for each
bacterium in different concentrations) are significantly different
(P < 0.05). Na: Not active.
Experiment was performed in triplicate and expressed as mean SD.
Values with different superscripts within each column (for each
bacterium in different concentrations) are significantly different
(P < 0.05). Na: Not active.
Table 7 Antibacterial activity of complex 3
Inhibition zone (mm)
Table 10 Antibacterial activity of complex 6
Concentration
Concentration
Concentration
(0.01 mg ml−1
)
Microorganism
(1 mg ml−1
)
(0.1 mg ml−1
)
Inhibition zone (mm)
P. vulgaris (−)
E. coli (−)
12 0.34a
12 0.45a
10 0.22a
11 0.28a
10 0.15b
10 0.18b
8
7
Na
9
7
0.11c
0.14c
Concentration
Concentration
Concentration
(0.01 mg ml−1
)
Microorganism
(1 mg ml−1
)
(0.1 mg ml−1
)
B. cereus (+)
S. aureus (+)
9
0.18b
10 0.4b
0.14b
10 0.24b
0.16c
0.00c
0.11c
P. vulgaris (−)
E. coli (−)
B. cereus (+)
S. aureus (+)
12 0.34a
12 0.56a
10 0.22a
11 0.18a
10 0.22b
8
7
0.11c
0.00c
B. megaterium (+) 10 0.18a
S. marcescens (−) 12 0.12a
9
8
7
0.16b
0.00b
7
Na
8
Na
7
10 0.14b
0.18c
0.00c
Experiment was performed in triplicate and expressed as mean SD.
Values with different superscripts within each column (for each
bacterium in different concentrations) are significantly different
(P < 0.05). Na: Not active.
B. megaterium (+) 12 0.25a
9
0.12b
10 0.24b
S. marcescens (−)
13 0.28a
Experiment was performed in triplicate and expressed as mean SD.
Values with different superscripts within each column (for each
bacterium in different concentrations) are significantly different
(P < 0.05). Na: Not active.
Preparation of [Me2SCHC(O)C6H4-m-NO2]. To an acetone
solution (10 ml) of dimethylsulfide (0.062 g, 1.00 mmol) was
added 2-bromo-3′-nitroacetophenone (0.244 g, 1.00 mmol) and
the mixture was stirred for 12 h. The solid product (sulfonium
salt) was isolated by filtration, washed with ether and dried
under reduced pressure. Further treatment with aqueous 10%
NaOH solution led to elimination of HBr, giving the free
ligand. Yield 0.168 g, 75%. Anal. Calc for C10H11O3SN:
C, 53.32; H, 4.92. Found: C, 53.01; H, 4.85. M.p. 110–112 C. IR
(KBr disk): ν (cm−1) 1583 (CvO). 1H NMR (CDCl3): δ (ppm)
2.98 (s, 6H, S(CH3)2); 4.36 (1H, CH); 7.41 (m, 2H, Ph); 8.12 (dd,
3JHH = 3.6 Hz, 1H, Ph); 8.54 (s, 1H, Ph). 13C-NMR (CDCl3,
ppm): δ 28.28 (s, S(CH3)2); 55.40 (s, CH); 120.72 (s, Ph); 123.20
2526 | Dalton Trans., 2013, 42, 2520–2529
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Table 11 Antibacterial activities of antibiotics as positive controls and DMSO as negative control
Inhibition zone (mm)
Positive controls
Negative control
DMSO
Microorganism
Gentamicin
Penicillin
Nitrofurantion
Neomycin
P. vulgaris (−)
E. coli (−)
30 0.14
Na
25 0.18
35 0.24
25 0.33
27 0.18
Na
Na
Na
Na
Na
Na
15 0.22
25 0.22
10 0.12
30 0.34
20 0.28
18 0.14
22 0.16
20 0.33
20 0.36
25 0.45
20 0.55
22 0.28
Na
Na
Na
Na
Na
Na
B. cereus (+)
S. aureus (+)
B. megaterium (+)
S. marcescens (−)
Experiment was performed in triplicate and expressed as mean SD. Na: Not active.
3
(s, Ph); 128.38 (s, Ph); 131.98 (s, Ph); 142.29 (s, Ph); 147.55 (s, 3JHH = 8.9 Hz, 2H, Ph); 8.19 (d, JHH = 8.9 Hz, 2H, Ph).
Ph); 178.05 (s, CO).
13C-NMR (DMSO-d6, ppm): δ 28.05 (s, S(CH3)2); 57.34 (s, CH);
Preparation of complex [AgNO3(Me2SCHC(O)C6H5)]n (1). To 123.11 (s, Ph(m)); 127.46 (s, Ph(o)); 144.96 (s, Ph(i)); 147.95
a dichloromethane solution (15 ml) of AgNO3 (0.169 g, (s, Ph(p)); 180.19 (s, CO).
1.00 mmol) was added a methanolic solution (10 ml) of ylide
Preparation of complex [Ag(Me2SCHC(O)C6H4-p-OMe)2]NO3
Me2SCHC(O)C6H5 (0.180 g, 1.0 mmol). The solution was pro- (4). Complex 4 was prepared following the same method
tected from light with aluminum foil and stirred at room used for 1. Thus, AgNO3 (0.168 g, 1.00 mmol) was reacted
temperature. After 3–4 h the mixture was filtered through with ylide Me2SCHC(O)C6H4-p-OMe (0.420 g, 2.0 mmol)
Celite and the filtrate concentrated to 3–5 ml. Addition of giving 4.
petroleum ether (15–30 ml) precipitated the product.
Yield 0.407 g, 69%. Anal. Calc for AgNO7S2C22H28: C, 44.75;
Yield 0.213 g, 61%. Anal. Calc for AgNO4SC10H12: C, 34.30; H, 4.78; N, 2.37. Found: C, 45.25; H, 5.0; N, 2.3. Decomposition
H, 3.45; N, 4.00. Found: C, 34.06; H, 3.50; N, 3.89. Decompo- at 136–138 °C. IR (KBr disk): ν (cm−1) 1661 (CO). 1H-NMR
sition at 120–122 °C. IR (KBr disk): ν (cm−1) 1668 (CO). (CDCl3, ppm): δ 3.77 (s, 3H, OCH3); 2.75 (s, 6H, S(CH3)2); 4.78
3
3
1H-NMR (CDCl3, ppm): δ 2.86 (s, 6H, S(CH3)2); 4.69 (s, 1H, (s, 1H, CH); 6.70 (d, JHH = 8.9 Hz, 2H, Ph); 7.79 (d, JHH
=
CH); 7.32 (dd, JHH = 7.8 Hz, 2H, Ph); 7.41 (dd, JHH = 7.8 Hz, 8.9 Hz, 2H, Ph). 13C-NMR (DMSO-d6, ppm): δ 28.43 (s, S(CH3)2);
3
3
1H, Ph); 7.84 (d, JHH = 8.0 Hz, 3H, Ph). 13C-NMR (DMSO-d6, 53.75 (s, CH); 55.73 (s, OCH3); 113.64 (s, Ph(p)); 129.00 (s,
3
ppm): δ 28.28 (s, S(CH3)2); 54.12 (s, CH); 127.11 (s, Ph(p)); Ph(m)); 130.83 (s, Ph(o)); 162.01 (s, Ph(i)); 187.94 (s, CO).
128.57 (s, Ph(m)); 131.66 (s, Ph(o)); 138.15 (s, Ph(i)); 188.74
(s, CO).
Preparation of complex [AgNO3(Me2SCHC(O)C6H4-p-Me)]n
(5). Complex 5 was prepared following the same method used
Preparation of complex [Ag(Me2SCHC(O)C6H4-m-NO2)2]2- for 1. Thus, AgNO3 (0.168 g, 1.00 mmol) was reacted with ylide
(NO3)2·2H2O (2). Complex 2 was prepared following the same Me2SCHC(O)C6H4-p-Me (0.194 g, 1.0 mmol) giving 5.
method used for 1. Thus, AgNO3 (0.168 g, 1.00 mmol)
was reacted with ylide Me2SCHC(O)C6H4-m-NO2 (0.448 g, 36.28; H, 3.87; N, 3.58. Found: C, 36.9; H, 3.80; N, 3.80. M.p.
2.0 mmol) giving 2.
111–112 °C. IR (KBr disk): ν (cm−1) 1671 (CO). 1H-NMR
Yield 0.209 g, 75%. Anal. Calc for Ag2N2O8S2C22H28: C,
Yield 0.415 g, 67%. Anal. Calc for C20H22AgN3O9S2: (CDCl3, ppm): δ 2.30 (s, 3H, CH3); 2.76 (s, 6H, S(CH3)2); 4.84 (s,
C, 38.72; H, 3.57; N, 6.77. Found: C, 38.59; H, 3.64; N, 6.65. 1H, CH); 7.16 (d, 3JHH = 8.1 Hz, 2H, Ph); 7.74 (d, 3JHH = 8.1 Hz,
M.p. 168–170 °C. IR (KBr disk): ν (cm−1) 1686 (CO). 1H-NMR 2H, Ph). 13C-NMR (DMSO-d6, ppm): δ 21.66 (s, CH3); 26.98 (s,
(DMSO-d6, ppm): δ 2.84 (s, 6H, S(CH3)2); 5.04 (br, 1H, CH); S(CH3)2); 52.50 (s, CH); 128.20 (s, Ph(p)); 129.52 (s, Ph(m));
7.67 (m, 2H, Ph); 8.20 (m, 1H, Ph); 8.54 (s, 1H, Ph). 13C-NMR 132.45 (s, Ph(o)); 144.20 (s, Ph(i)); 192.97 (s, CO).
(DMSO-d6, ppm): δ 28.36 (s, S(CH3)2); 55.15 (s, CH); 121.17
(s, Ph)); 125.42 (s, Ph); 130.10 (s, Ph)); 133.10 (s, Ph); 139.93 Complex 6 was prepared following the same method used for
(s, Ph); 148.04 (s, Ph); 183.39 (s, CO). 1. Thus, AgNO3 (0.168 g, 1.00 mmol) was reacted with ylide
Preparation of complex [Ag(Me2SCHC(O)C6H4-p-NO2)2]2- Me2SCHC(O)C6H4-p-Br (0.259 g, 1.0 mmol) giving 6.
[{AgNO3(μ-NO3)(Me2SCHC(O)C6H4-p-NO2)}2]·2CH3OH (3). Yield 0.334 g, 78%. Anal. Calc for AgNO4BrSC10H11: C,
Preparation of complex [AgNO3Me2SCHC(O)C6H4-p-Br] (6).
Complex 3 was prepared following the same method used for 27.99; H, 2.58; N, 3.26. Found: C, 28.5; H, 2.7; N, 2.90.
1. Thus, AgNO3 (0.336 g, 2.00 mmol) was reacted with ylide Decomp. 114–117 °C. IR (KBr disk): ν (cm−1) 1678 (CO).
Me2SCHC(O)C6H4-p-NO2 (0.672 g, 3.0 mmol) giving 3.
1H-NMR (CDCl3, ppm): δ; 2.81 (s, 6H, S(CH3)2); 4.80 (s, 1H,
Yield 0.731 g, 72%. Anal. Calc for Ag4N10O30S6C60H66: C, CH); 7.37 (d, 3JHH = 8.1 Hz, 2H, Ph); 7.68 (d, 3JHH = 8.1 Hz, 2H,
35.48; H, 3.28; N, 6.90. Found: C, 35.12; H, 3.35; N, 6.74. M.p. Ph). 13C-NMR (DMSO-d6, ppm): δ 28.20 (s, S(CH3)2), 53.68 (s,
109–110 °C. IR (KBr disk): ν (cm−1) 1675 (CO). 1H-NMR CH), 125.31 (s, Ph(m)); 129.16 (s, Ph(p)); 131.49 (s, Ph(i));
(CDCl3, ppm): δ 3.02 (s, 6H, S(CH3)2); 4.40 (s, 1H, CH); 7.88 (d, 137.08 (s, Ph(o)); 187.29 (s, CO).
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alternative system of medicine. However, possible deleterious
side-effects of these compounds on human health must be
further investigated. Future research will involve studies on
X-ray crystallography
2.2. X-ray crystallography
Data collection from suitable crystals of 1, 2 and 3 was per- possible modification of these complexes to increase their
formed on an Oxford Diffraction single-crystal X-ray diffracto- antibacterial activity.
meter using mirror monochromated Cu and Mo Kα radiation
(1.54184 and 0.71073 Å, respectively) at 130 K (Table 1). Gaus-
sian absorption corrections were carried out using a multi-
faceted crystal model, using CrysAlisPro.36 All three structures
were solved by direct methods and refined by the full-matrix
Acknowledgements
least-squares method on F2 using the SHELXTL-97 crystallo- We are grateful to the Bu-Ali Sina University for a grant and
graphic package.37,38 All non-hydrogen atoms were refined an- Mr Zebarjadian for recording the NMR spectra. F. Akhlaghi
isotropically. Hydrogen atoms were inserted at calculated Bagherjeri thanks the University of Melbourne for hosting her
positions using a riding model, with isotropic displacement as an exchange visitor.
parameters.
Antibacterial activity
The potential antibacterial effects of the complexes were inves-
tigated by agar disc diffusion method against three Gram
Notes and references
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