Syntheses, crystal structures, and antimicrobial activities of nickel(II) and cadmium(II) complexes with 4-methylsulfonyl cinnamate and diamines

Article abstract of DOI:10.1080/00958972.2012.744001

Two metal complexes, [Ni^II(mscinn)₂(pda)₂] (1) and [Cd^II(mscinn)₂(dmeda)₂·2H ₂O] (2) (mscinn=4-methylsulfonyl cinnamate, pda=propane-1,3-diamine, dmeda=N′, N′-dimethylethane-1,2-diamine), were synthesized by reacting 4-methylsulfonyl cinnamate with the diamines and metal salts. Their structures were determined by single-crystal X-ray diffraction analysis. Crystal parameters of 1: C₂₆H₃₈N₄NiO₈S ₂, M=657.43, monoclinic, P2₁/c, a=16.6123(8) A, b=8.5956(4) A, c=11.2047(5) A, β=107.423(1)°, V=1526.54(12) A³, Z=2, D_calcd=1.430 g cm^-3, F(000)=692, μ=0.825mm^-1, R₁=0.0257, wR ₂=0.0669. Crystal data of 2: C₂₈H₄₂CdN ₄O₈S₂ · 2(H₂O), M=775.24, monoclinic, P2₁/c, a=9.8278(4) A, b=11.6611(5) A, c=15.3972(7) A, β=96.195(1)°, V=1754.26(13) A³, Z=2, D_calcd=1.468 g cm^-3, F(000)=804, μ=0.798mm ^-1, R₁=0.0299, wR₂=0.0770. Antimicrobial activities for 1 and 2 against Escherichia coli, Pseudomonas putida, Bacillus subtilis, and Bacillus cereus had better antibacterial activity than their parent carboxylic acid against Gram-positive bacteria (B. subtilis and B. cereus). The cadmium complex of the cinnamate displayed high inhibitory activity with an MIC value of 5 μgmL^-1 against P. putida, while the nickel complex also exhibited good inhibitory potency with an MIC value of 5 μgmL^-1 against B. subtilis.

Full text of DOI:10.1080/00958972.2012.744001

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Syntheses, crystal structures, and
antimicrobial activities of nickel(II)
and cadmium(II) complexes with 4-
methylsulfonyl cinnamate and diamines
a
a
a
a
Shao-Song Qian , Yue-Hu Chen , Qi-Peng Long , Fang Wang
&
a
Hai-Liang Zhu
a
School of Life Sciences, Shandong University of Technology ,
Zibo 255049 , China
Accepted author version posted online: 30 Oct 2012.Published
online: 16 Nov 2012.
To cite this article: Shao-Song Qian , Yue-Hu Chen , Qi-Peng Long , Fang Wang & Hai-Liang Zhu
(
2012) Syntheses, crystal structures, and antimicrobial activities of nickel(II) and cadmium(II)
complexes with 4-methylsulfonyl cinnamate and diamines, Journal of Coordination Chemistry,
5:24, 4419-4429, DOI: 10.1080/00958972.2012.744001
6
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Journal of Coordination Chemistry
Vol. 65, No. 24, 20 December 2012, 4419–4429
Syntheses, crystal structures, and antimicrobial activities of
nickel(II) and cadmium(II) complexes with 4-methylsulfonyl
cinnamate and diamines
SHAO-SONG QIAN, YUE-HU CHEN, QI-PENG LONG, FANG WANG
and HAI-LIANG ZHU*
School of Life Sciences, Shandong University of Technology, Zibo 255049, China
(
Received 19 May 2012; in final form 17 September 2012)
II
[Ni (mscinn)
II
[Cd (mscinn)
Two
metal
complexes,
2
(pda)
2
]
(1)
and
2
(dmeda)
2
0
ꢀ
2
H
2
O] (2) (mscinn ¼ 4-methylsulfonyl cinnamate, pda ¼ propane-1,3-diamine, dmeda ¼ N ,
0
N -dimethylethane-1,2-diamine), were synthesized by reacting 4-methylsulfonyl cinnamate
with the diamines and metal salts. Their structures were determined by single-crystal X-ray
diffraction analysis. Crystal parameters of 1: C26
˚
H
38
˚
N
4
NiO
8
S
2
, M ¼ 657.43, monoclinic,
˚
ꢁ
˚
3
P2 /c, a ¼ 16.6123(8) A, b ¼ 8.5956(4) A, c ¼ 11.2047(5) A, ꢀ ¼ 107.423(1) , V ¼ 1526.54(12) A ,
Z ¼ 2, Dcalcd ¼ 1.430 g cm , F(000) ¼ 692, ꢁ ¼ 0.825 mm , R
1
ꢂ3
ꢂ1
1
¼ 0.0257, wR ¼ 0.0669. Crystal
2
˚
data of 2:
b ¼ 11.6611(5) A,
C
28
H
42CdN
c ¼ 15.3972(7) A,
4
O
8
S
2
ꢀ 2(H
2
˚
O), M ¼ 775.24, monoclinic, P2
1
/c, a ¼ 9.8278(4) A,
ꢁ
˚
3
˚
ꢀ ¼ 96.195(1) ,
V ¼ 1754.26(13) A ,
Z ¼ 2,
ꢂ3
ꢂ1
D
calcd ¼ 1.468 g cm , F(000) ¼ 804, ꢁ ¼ 0.798 mm , R
1
¼ 0.0299, wR ¼ 0.0770. Antimicrobial
2
activities for 1 and 2 against Escherichia coli, Pseudomonas putida, Bacillus subtilis, and Bacillus
cereus had better antibacterial activity than their parent carboxylic acid against Gram-positive
bacteria (B. subtilis and B. cereus). The cadmium complex of the cinnamate displayed high
ꢂ1
inhibitory activity with an MIC value of 5 mg mL against P. putida, while the nickel complex
ꢂ1
also exhibited good inhibitory potency with an MIC value of 5 mg mL against B. subtilis.
Keywords: 4-Methylsulfonyl cinnamate; Nickel; Cadmium; X-ray analysis
1. Introduction
Cinnamic acid is a natural product found in fragrances used in decorative cosmetics,
fine fragrances, shampoos, toilet soaps, and other toiletries as well as in non-cosmetic
products such as household cleaners and detergents [1]. In addition, cinnamic acid and
its derivatives have attracted interest for their biological activities. These compounds
have been reported to have anti-inflammatory and antimicrobial activities against
microorganisms such as rumen bacteria or lactobacilli [2–5]. Moreover, anti-inflamma-
tory and antibacterial activities of metal(II) complexes were higher than in the parent
carboxylic acids [6–8] and the anti-bacterial effect of some drugs could be enhanced and
overcome resistance when they were chelated to a metal [9, 10]. Cd(II), Ni(II), Cu(II),
Co(II), Zn(II), etc., can be coordinated with a series of ligands, possessing antibacterial
*
Corresponding author. Email: hailiang_zhu@163.com
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2012 Taylor & Francis
http://dx.doi.org/10.1080/00958972.2012.744001

4
420
S.-S. Qian et al.
activities [11, 12]. It is important to gain knowledge about the structure and bonding
relations of the complexes for the preparation of effective anti-microbial species.
However, only a few metal complexes with cinnamate derivatives as ligand or co-ligand
have been structurally characterized [13–16]. In this work, we prepare
-methylsulfonyl cinnamate by reacting 4 -(methylsulfonyl)benzaldehyde with malonic
acid and then synthesized metal complexes with Ni(II), Cd(II), and organic diamines.
a
4
II
II
Here we report crystal structures of [Ni (mscinn) (pda) ] (1) and [Cd (mcinn)
2
2
2
(
dmeda)2 (2) (mscinn ¼ 4-methylsulfonyl cinnamate, pda ¼ propane-1,3-diamine,
0
0
dmeda ¼ N ,N -dimethylethane-1,2-diamine) and their antimicrobial activities against
Escherichia coli, Pseudomonas putida, Bacillus subtilis, and Bacillus cereus. The
antibacterial activity of 1 and 2 was lower than the parent 4-methylsulfonyl cinnamate
against Gram-negative bacteria (E. coli and P. putida), but they had better antibacterial
activity than their parent carboxylic acid against Gram-positive bacteria (B. subtilis and
B. cereus). Especially, the cadmium complex displayed high inhibitory activity with an
MIC value of 5 mg mL against P. putida, while the nickel complex also exhibited good
inhibitory potency with an MIC value of 5 mg mL against B. subtilis, indicating that
these complexes are potent antimicrobial agents.
ꢂ1
ꢂ1
2
2
. Experimental
.1. General
All reagents, unless otherwise stated, were purchased as AR grade and used without
purification. Elemental analysis was conducted on a Perkin-Elmer 240 C elemental
ꢂ1
analyzer; IR spectra were recorded (400–4000 cm ) on a FT-IR Nicolet 5700
1
spectrometer; H-NMR measurement was made on an AV-300 BRUKER spectro-
meter; UV-Vis spectra were recorded on a UV-3600 spectrophotometer (Shimadzu);
ESI mass spectra were obtained on a Mariner System 5304 mass spectrometer; melting
points were recorded on a WRS-1B Digital Melting Point Apparatus.
2
.2. Synthesis
The syntheses of 1 and 2 are outlined in scheme 1.
2.2.1. Synthesis of 4-methylsulfonyl cinnamate. The synthesis is performed according
to the literature [17] with modification. Malonic acid (10.5 g, 0.1 mol) and
4
5
-(methylsulfonyl)benzaldehyde (18.4 g, 0.1 mol) in ethanol (50 mL) were added in a
00-mL-round-bottomed flask, fitted with a reflux condenser and a thermometer.
ꢁ
Pyridine (5 mL) was then added and the mixture was heated under reflux (90–95 C)
ꢁ
for 12 h. The reaction mixture was cooled to 0 C and light-yellow crystals precipitated
were separated by filtration and washed four times with 20 mL portions of cold water.
ꢁ
The product was dried at 60–70 C. The yield was 18 g (80%) of 4-methylsulfonyl
ꢁ
cinnamate, m.p. ¼ 286.8–288.0 C, without further purification for the next synthesis of
metal complexes.

4
-Methylsulfonyl cinnamate
4421
Scheme 1. Synthesis of 1 and 2.
2.2.2. Synthesis of 1. 4-Methylsulfonyl cinnamate (0.01 mol, 2.26 g) and
sodium hydroxide (0.4 g) were dissolved in water (30 mL) and then a nickel sulfate
ꢂ1
solution (0.25 mol L , 20 mL) was added dropwise with stirring. The precipitate was
collected by filtration and washed thrice with 5 mL portions of cold water. The nickel
ꢁ
4
-methylsulfonyl cinnamate was dried at 60–70 C to yield 1.6 g (62.7%) of compound 1.
The nickel 4-methylsulfonyl cinnamate (0.0511 g, 0.1 mmol) was added to a methanol
solution (15 mL) of 1,3-propylene diamine (0.1 mmol, 0.0072 g). The mixture was stirred
at room temperature for 1 h to give a clear blue solution. After keeping the solution in air
for 7 days, blue block-shaped crystals were formed at the bottom of the vessel on slow
evaporation of the solvent. The yield was 42.2%. Anal. Calcd for C H N NiO S (%):
2
6
38
4
8 2
ꢂ1
C, 47.02; H, 5.77; N, 8.44. Found (%): C, 47.38; H, 5.74; N, 7.52. IR (cm ): 3288.6
ꢂ
ꢂ(NH, stretching), 2926.2 ꢂ(Ar–CH), 1640.7 ꢂ(NH, deformation), 1595.1 ꢂ (COO ),
as
ꢂ
1
556.3 ꢂ(Ar–C¼C), 1437.0 ꢂ(Ar–C¼C), 1409.9 ꢂ (COO ), 1320.7 ꢂ (SO ), 1155.2
s
as
2
þ
ꢂ (SO ), 1021.7 ꢂ(C–N), 541.8 ꢂ(O–M), 440.3 ꢂ(N–M). MS (ESI): 658.4 ([M þ H] ).
s
2
UV-Vis (DMSO, ꢃ
(nm)): 221, 277.
max
2
.2.3. Synthesis of 2. Complex 2 was synthesized analogously to that of 1 by using
cadmium 4-methylsulfonyl cinnamate instead of nickel 4-methylsulfonyl cinnamate and
0
0
employing N ,N -dimethylethane-1,2-diamine instead of 1,3-propylene diamine.
Colorless block-shape crystals were obtained at the bottom of the vessel on slow
evaporation of the solvent. The yield is 48.1%. Anal. Calcd for C H CdN O S ꢀ
2
8
42
4
8 2
2
(H O) (%): C, 46.06; H, 6.63; N, 7.67. Found (%): C, 46.25; H, 6.58; N, 7.43.
2

4
422
S.-S. Qian et al.
Table 1. Crystallographic data and details of diffraction experiments for 1 and 2.
1
2
Empirical formula
Color
Formula weight
Crystal system
Space group
C
26
H
38
N
4
NiO
8
S
2
C
28
H
42CdN
4
O
8
S
2
ꢀ2(H
2
O)
Blue
657.43
Monoclinic
P2 /c
Colorless
775.24
Monoclinic
1
1
P2 /c
˚
ꢁ
Unit cell dimensions (A, )
a
b
c
ꢅ
ꢀ
ꢆ
16.6123(8)
8.5956(4)
11.2047(5)
90
107.423(1)
90
1526.54(12), 2
692
1.4827(1)
0.825
296(2)
9.8278(4)
11.6611(5)
15.3972(7)
90
96.195(1)
90
1754.26(13), 2
804
1.4677(1)
0.798
296(2)
3233
2959
208
2.7–25.0
3
˚
Volume (A ), Z
F(000)
Calculated density (g cm
Absorption coefficient (mm
Temperature (K)
Reflections collected
Independent reflection
Refined parameters
ꢇ range for data collection ( )
Final R indices [I 4 2ꢈ(I)]
R indices (all data)
ꢂ3
)
ꢂ1
)
2588
2433
188
2.7–25.0
ꢁ
R
R
1
1
¼ 0.0257, wR
2
2
¼ 0.0657
¼ 0.0669
R
R
1
1
¼ 0.0299, wR
2
2
¼ 0.0740
¼ 0.0770
¼ 0.0271, wR
¼ 0.0328, wR
2
Goodness-of-fit on F
Largest difference peak and hole (e A
1.03
0.33 and ꢂ0.21
1.07
0.82 and ꢂ0.40
ꢂ3
˚
)
1
H-NMR (DMSO-d , ꢄ (ppm)): 7.842–7.914 (m, 4H, Ar–H), 7.456 (d, 1H, CH¼), 6.716
6
(
d, 1H, CH¼), 3.269 (s, 3H, –SO –CH ), 2.421–2.730 (m, 4H, –CH –), 2.275 (s, 6H,
2
3
2
ꢂ1
ꢂCH ); IR (KBr, ꢂ (cm )): 3420.9 ꢂ(OH, water) 3264.9 ꢂ(NH, stretching), 2925.6
3
ꢂ
ꢂ(Ar–CH), 1644.1 ꢂ(NH, deformation), 1545.6 ꢂ (COO ), 1411.4 ꢂ(Ar–C¼C), 1393.7
as
ꢂ
ꢂ (COO ), 1305.7 ꢂ (SO ), 1183.4 ꢂ(C–N), 1149.5 ꢂ (SO ), 535.7 ꢂ(O–M), 430.2
s
s
as
2
2
þ
ꢂ(N–M). MS (ESI): 758.3 ([M þ H] ). UV-Vis (DMSO, ꢃ
(nm)): 223, 278.
max
2
.3. Structure determination
The data were collected on a Bruker D8 VENTURE PHOTON diffractometer with
˚
graphite-monochromated Mo-Ka radiation (ꢃ ¼ 0.71073 A) using the Genenic omega
2
scan technique. The structure was solved by direct methods and refined on F by
full-matrix least-squares with Bruker’s SHELXL-97 program [18]. All nonhydrogen
atoms were refined anisotropically. All hydrogen atoms were treated using a riding
model. Experimental details for X-ray data collection of 1 and 2 are presented in
table 1. For further details on the crystal structure investigations of 1 and 2, see the
section ‘‘Supplementary material.’’
2
.4. Antimicrobial activity
The antibacterial activities of the compounds were tested against E. coli, P. putida,
B. subtilis, and B. cereus using the Mueller–Hinton medium (MH medium: casein

4
-Methylsulfonyl cinnamate
4423
Figure 1. The structure of 1 and 2.
hydrolysate 17.5 g, soluble starch 1.5 g, beef extract 2.0 g, distilled water 1000 mL).
The MICs of the test compounds were determined by a colorimetric method using the
dye 3 -(4,5-dimethylthiazol-2-yl)-2,5-diphenyl trtrazolium bromide (MTT) [19]. A stock
ꢂ1
solution of the synthesized compound (50 mg mL ) in DMSO was prepared and graded
quantities of the test compounds were incorporated in a specified quantity of sterilized
MH medium. A specified quantity of the medium containing the test compound was
poured into microtitration plates. Suspension of the microorganism was prepared to
5
ꢂ1
contain approximately 10 cfu mL and applied to microtitration plates with serially
ꢁ
diluted compounds in DMSO to be tested and incubated at 37 C for E. coli and
ꢁ
B. subtilis, at 30 C for P. putida, and B. cereus for 24 h. After the MICs were visually
determined on each microtitration plate, 50 mL of Phosphate Buffered Saline
ꢂ1
(
PBS 0.01 molL , pH 7.4, 2.9 g of Na HPO ꢀ 12H O, 0.2 g of KH PO , 8.0 g of
2
4
2
2
ꢂ1
4
NaCl, 0.2 g of KCl, 1000 mL of distilled water) containing 2 mgmL of MTT was
added to each well. Incubation was continued at room temperature for 4–5 h.

4
424
S.-S. Qian et al.
˚
Table 2. Selected bond lengths (A) and angles ( ) for 1.
ꢁ
Ni(1)–O(1)
Ni(1)–N(1)
Ni(1)–N(2)
S(1)–O(3)
S(1)–O(4)
S(1)–C(1)
S(1)–C(13)
O(1)–C(9)
O(2)–C(9)
N(1)–C(10)
N(2)–C(12)
2.0969(12)
2.1124(15)
2.1040(14)
1.4247(17)
1.4245(15)
1.7680(18)
1.744(3)
1.256(2)
1.245(2)
1.477(3)
1.475(2)
C(1)–C(2)
C(1)–C(6)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(4)–C(7)
C(5)–C(6)
C(7)–C(8)
C(8)–C(9)
C(10)–C(11)
C(11)–C(12)
1.381(2)
1.375(3)
1.377(3)
1.390(2)
1.388(2)
1.464(2)
1.381(3)
1.318(2)
1.492(2)
1.511(3)
1.508(2)
O(1)–Ni(1)–N(1)
O(1)–Ni(1)–N(2)
N(1)–Ni(1)–N(2)
O(3)–S(1)–O(4)
O(3) –S(1)–C(1)
O(3) –S(1)–C(13)
O(4)–S(1)–C(1)
O(4)–S(1)–C(13)
C(1) –S(1)–C(13)
C(2)–C(1)–C(6)
90.64(6)
88.88(5)
86.06(6)
118.33(10)
108.34(9)
108.52(12)
108.18(8)
107.96(12)
104.67(11)
120.29(17)
Ni(1)–O(1)–C(9)
Ni(1)–N(1)–C(10)
Ni(1)–N(2)–C(12)
S(1)–C(1)–C(2)
S(1)–C(1)–C(6)
C(2)–C(3)–C(4)
C(3)–C(4)–C(5)
C(3)–C(4)–C(7)
O(1)–C(9)–O(2)
N(1)–C(10)–C(11)
132.37(12)
117.65(11)
118.24(11)
119.36(13)
120.35(13)
121.42(17)
117.85(16)
121.83(15)
125.50(16)
111.49(17)
The content of each well was removed, and 100 mL of isopropanol containing 5% of
ꢂ1
1
temperature, the optical density (OD) was measured with a microplate reader at
mol L
HCl was added to extract the dye. After 12 h of incubation at room
5
50 nm. The observed MICs are presented in table 5.
3
3
. Results and discussion
.1. Single crystal X-ray diffraction analysis
Complexes 1 and 2 display similar structures, although different metal ions and diamine
ligands were employed during the synthetic procedure.
3.1.1. Structure of 1. Single-crystal X-ray diffraction analyses revealed that 1
consisted of half molecule of C H N NiO S in the asymmetric unit. The molecular
2
6
38
4
8 2
structure of 1 is shown in figure 1. The complex crystallizes in monoclinic space group
P2 /c with two formula units in the unit cell. Selected bond lengths and angles are given
1
in table 2. The coordination sphere of nickel is composed of two oxygen atoms from
two 4-methylsulfonyl cinnamate ligands and four nitrogen atoms from two
1,3-propylene diamines. The 4-methylsulfonyl cinnamate is monodentate with the
Ni–O bond length (2.0969(12) A), slightly longer than 2.06 A (normal distance of Ni–O)
˚
˚
[
the 1,3-propylene diamine ligand, the O1–Ni1–N1 and O1–Ni1–N2 angles (90.64(6)
20]. Due to small steric hindrance between the uncoordinated carboxylate oxygen and
ꢁ
ꢁ
ꢁ
and 88.88(5) , respectively) are close to the ideal 90 values.
Complex 1 is linked to infinite 1-D chains running along the crystallographic b-axis
(figure 2a). The chains are connected by intermolecular N1–H1Bꢀ ꢀ ꢀO2 and

4
-Methylsulfonyl cinnamate
4425
Figure 2. (a) View of the 1-D chains of 1 running along the b-axis; (b) hydrogen bonds connecting adjacent
chains to a 2-D network in the c-axis (hydrogen atoms are omitted for clarity).
N2–H2Aꢀ ꢀ ꢀO2 hydrogen bonds in the c direction to form a 2-D network (figure 2b).
In addition, intramolecular N1–H1Aꢀ ꢀ ꢀO2 and N2–H2Bꢀ ꢀ ꢀO2 hydrogen bonds
contribute to the stability of the crystal structure of 1 (table 3).
3
.1.2. Structure of 2. The structure of 2 is shown in figure 1. Complex 2 crystallizes in
the monoclinic space group P2 /c with one-half of C H CdN O S ꢀ2H O and a water
1
28 42
4
8
2
2
molecule in the asymmetric unit. Selected bond lengths and angles are given in table 4.
Each Cd(II) is octahedrally coordinated by two carboxylate oxygen atoms and four
0
nitrogen atoms from two N,N -dimethylethane-1,2-diamine ligands. In the diamine,

4
426
S.-S. Qian et al.
˚
Table 3. Hydrogen-bonding geometry (A and ) for 1 and 2.
ꢁ
˚
Distance (D–A, A)
ꢁ
Bond
Angle ( )
Symmetry code
Complex 1
N(1)–H(1 A)ꢀ ꢀ ꢀO(2)
N(1)–H(1B)ꢀ ꢀ ꢀO(2)
N(2)–H(2 A)ꢀ ꢀ ꢀO(2)
N(2)–H(2B)ꢀ ꢀ ꢀO(2)
3.238(2)
3.041(2)
3.051(2)
3.0105(19)
134
170
159
143
ꢂx, 1 ꢂ y, 2 ꢂ z
ꢂx, ꢂ1/2 þ y, 3/2 ꢂ z
x, 3/2 ꢂ y, 1/2 þ z
ꢂx, 1 ꢂ y, 2 ꢂ z
Complex 2
N(2)–H(2 A)ꢀ ꢀ ꢀO(5)
N(2)–H(2B)ꢀ ꢀ ꢀO(2)
O(5)–H(5B)ꢀ ꢀ ꢀO(1)
C(8)–H(8 C)ꢀ ꢀ ꢀO(3)
C(8)–H(8 A)ꢀ ꢀ ꢀO(2)
C(13)–H(13 A)ꢀ ꢀ ꢀO(3)
C(14)–H(14B)ꢀ ꢀ ꢀO(4)
3.178(4)
2.970(3)
2.847(3)
3.316(4)
3.415(4)
3.183(4)
3.438(5)
148
137
120
165
145
121
156
x, 3/2 ꢂ y, ꢂ1/2 þ z
1 ꢂ x, 1/2 þ y, 1/2 ꢂ z
ꢂ1 ꢂ x, 1 ꢂ y, 1 ꢂ z
ꢂx, ꢂ1/2 þ y, 1/2 ꢂ z
1 þ x, 3/2 ꢂ y, ꢂ1/2 þ z
1 þ x, 1/2 ꢂ y, ꢂ1/2 þ z
˚
Table 4. Selected bond lengths (A) and angles ( ) for 2.
ꢁ
Cd(1)–O(1)
Cd(1)–N(1)
S(1)–O(4)
S(1)–C(2)
S(1)–C(8)
O(1)–C(1)
O(2)–C(1)
N(1)–C(10)
N(1)–C(12)
N(1)–C(14)
N(2)–C(13)
2.418(2)
2.421(2)
1.429(2)
1.766(3)
1.748(3)
1.261(4)
1.240(4)
1.479(5)
1.443(4)
1.464(4)
1.467(5)
Cd(1)–N(2)
S(1)–O(3)
C(1)–C(3)
C(2)–C(4)
C(2)–C(9)
C(3)–C(5)
C(4)–C(7)
C(5)–C(6)
C(6)–C(7)
C(6)–C(11)
C(9)–C(11)
2.272(2)
1.437(2)
1.496(4)
1.383(5)
1.378(5)
1.276(5)
1.385(4)
1.484(4)
1.380(5)
1.385(5)
1.399(4)
O(1)–Cd(1)–N(1)
O(1)–Cd(1)–N(2)
N(1)–Cd(1)–N(2)
O(3)–S(1)–O(4)
O(3)–S(1)–C(2)
O(3)–S(1)–C(8)
O(4)–S(1)–C(2)
O(4)–S(1)–C(8)
C(2)–S(1)–C(8)
Cd(1)–O(1)–C(1)
90.66(7)
92.76(7)
77.77(8)
118.05(14)
108.33(14)
108.86(15)
108.55(14)
108.53(15)
103.57(14)
126.41(18)
Cd(1)–N(1)–C(10)
Cd(1)–N(1)–C(12)
Cd(1)–N(1)–C(14)
C(10)–N(1)–C(12)
C(10)–N(1)–C(14)
C(12)–N(1)–C(14)
Cd(1)–N(2)–C(13)
O(1)–C(1)–O(2)
109.16(18)
102.53(19)
114.0(2)
110.2(3)
106.5(3)
114.5(3)
108.94(18)
125.2(3)
119.6(3)
120.0(3)
O(1)–C(1)–C(3)
S(1)–C(2)–C(4)
N1 is different from N2, as the former is a tertiary amine. The steric hindrance for N1
connected with two methyl groups results in the distortion of the octahedron around
the cadmium. The most remarkable deviation from ideal was observed for N1–Cd–N2
ꢁ
˚
angles (77.77(8) ). For the same reason, Cd–N1 bond length (2.421(2) A) is longer than
2
˚
.272(2) A of the Cd–N2 bond, which is normal for the Cd–N bond [16]. The structure
of 2 is stabilized by a complicated hydrogen bonding network (figure 3). These
hydrogen bonds include not only classic N2–H2Aꢀ ꢀ ꢀO5 and O5–H5Bꢀ ꢀ ꢀO1 hydrogen
bonds (symmetry code: x, 3/2 ꢂ y, ꢂ1/2 þ z and 1 ꢂ x, 1/2 þ y, 1/2 ꢂ z, respectively), but
also weak C–Hꢀ ꢀ ꢀO hydrogen bonds (table 3). In addition, there are S1–O3ꢀ ꢀ ꢀꢉ
˚
interactions at 3.786(2) A of S1–O3 ! Cg(3) in 2. These hydrogen bonding, S1–O3ꢀ ꢀ ꢀꢉ
interactions, and van der Waals interactions lead to a 3-D network structure.

4
-Methylsulfonyl cinnamate
4427
Figure 3. The molecular structure of 2 drawn with 30% probability displacement ellipsoids for nonhydrogen
atoms (dashed lines indicate hydrogen bonds).
Table 5. MIC of 1 and 2 against the growth of four bacteria.
ꢂ1
Minimum inhibitory concentration (MIC, mg mL
)
Gram-negative
Gram-positive
Compounds
-Methylsulfonyl cinnamate
Propane-1,3-diamine
E. coli
P. putida
B. subtilis
B. cereus
4
2.5
50
50
450
50
10
50
10
5
30
450
50
450
10
5
10
20
30
40
50
450
5
10
15
10
50
450
450
50
10
5
15
0
N,N -Dimethylethane-1,2-diamine
Cadmium acetate
Nickel acetate
Complex 1
Complex 2
Streptomycin
3.2. IR spectra
Determination of carboxylate binding with the metal ions is made on the basis of the
value of separation between the asymmetric and symmetric carboxylate stretches,
D ¼ ꢂ
ꢂ
as(COO )
ꢂꢂ
ꢂ
s(COO )
. In 1 and 2, two bands attributing to the asymmetric
ꢂ1
carboxylate stretches (1595.1 and 1545.6 cm ) and two bands attributing to the
ꢂ1
symmetric carboxylate stretches (1409.9 and 1393.7 cm ) were observed. The D values
ꢂ1
ꢂ1
are 185.2 and 151.9 cm , respectively. The two D values (185 and 151.9 cm ) are
higher than the value for sodium cinnamate (143 cm ) [12], suggesting a monodentate
coordination of 4-methylsulfonyl cinnamate in 1 and 2.
ꢂ1
3
.3. Antimicrobial activity
For in vitro antimicrobial activity, 1 and 2 were tested against four bacteria. MIC
values are summarized in table 5. Comparative study of the ligand and their complexes

4
428
S.-S. Qian et al.
(
MIC values) showed that the antibacterial activity of the two metal complexes was not
higher than that for 4-methylsulfonyl cinnamate against Gram-negative bacteria (E. coli
and P. putida). However, they had better antibacterial activity than their parent
carboxylic acid against Gram-positive bacteria (B. subtilis and B. cereus). Cadmium
coordination of cinnamate displayed high inhibitory activity with an MIC value of
ꢂ1
5
mg mL against P. putida, while the nickel complex exhibited good inhibitory potency
ꢂ1
with an MIC value of 5 mg mL against B. subtilis.
Regarding the lower activity of the complexes than the parent p-methylsulfonyl
cinnamate against E. coli and P. putida and the higher activity than their parent
carboxylic acid against B. subtilis and B. cereus, we do not have a reasonable
explanation. Usually, bioactivities of metal complexes are higher than the ligands
themselves, which may explain the higher activity against B. subtilis and B. cereus.
Sometimes when metal ions combine with a potent organic compound, the metal ions
may act as slow releases, which may explain the lower activity of the complexes than the
parent p-methylsulfonyl cinnamate against E. coli and P. putida.
4
. Conclusion
Two metal complexes have been synthesized and characterized with an octahedral
geometry around metals and both crystallize in the monoclinic space group P2 /c.
The antibacterial activity indicated that the metal complexes were less effective than
1
4-methylsulfonyl cinnamate against E. coli and P. putida, but better than their parent
carboxylic acid against B. subtilis and B. cereus.
Supplementary material
CCDC 882 154 and CCDC 882 155 contain the supplementary crystallographic data for
C H N NiO S and C H CdN O S ꢀ2H O, respectively. These can be obtained free
2
6
38
4
8
2
28 42
4
8
2
2
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: þ44 -
(0)1223-336-033; Email: deposit@ccdc.cam.ac.uk).
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