Mixed ligand palladium(II) complexes of N-hydroxy-methylsaccharin (Sac-CH2OH): Synthesis, characterization and biological studies

Article abstract of DOI:10.1007/s11243-015-9988-0

Reaction of Na₂PdCl₄ with two equivalents of N-hydroxymethylsaccharin (Sac-CH₂OH) in the presence of NEt₃ afforded trans-[Pd(κ²-Sac-CH₂O)₂]. Further reaction of [Pd(κ²-Sac-CH₂O)₂] with one equivalent of diphosphine (L₂), Ph₂P(CH₂) _n PPh₂, (n = 1, dppm; 2, dppe and 3, dppp), Ph₂P(S)(CH₂)P(S)Ph₂ (dppmS₂) or Ph₂P(O)(CH₂)₂P(O)Ph₂ (dppeO₂) afforded mixed ligand complexes [Pd(κ¹-Sac-CH₂O)₂(L₂)], while reaction with two equivalents of Ph₃P, Ph₃PO or Ph₃PS (L) gave trans-[Pd(κ¹-Sac-CH₂O)₂(L)₂]. The N-hydroxymethylsaccharinate anion acts as a monodentate ligand, coordinating to the palladium center through the hydroxymethyl oxygen atom. The complexes were characterized by physico-chemical and spectroscopic methods. In addition, the free ligand N-hydroxymethylsaccharin and some of the complexes were screened in vitro for antibacterial activity.

Full text of DOI:10.1007/s11243-015-9988-0

Transition Met Chem
DOI 10.1007/s11243-015-9988-0
Mixed ligand palladium(II) complexes of N-hydroxy-
methylsaccharin (Sac-CH2OH): synthesis, characterization
and biological studies
Subhi A. Al-Jibori1 Ahmed S. Al-Janabi2 Sucharita Basak-Modi3
•
•
•
Samar S. Mohamed1 Harry Schmidt4
•
Received: 5 August 2015 / Accepted: 21 September 2015
Ó Springer International Publishing Switzerland 2015
Abstract Reaction of Na2PdCl4 with two equivalents of
N-hydroxymethylsaccharin (Sac-CH2OH) in the presence
of NEt3 afforded trans-[Pd(j2-Sac-CH2O)2]. Further reac-
tion of [Pd(j2-Sac-CH2O)2] with one equivalent of
diphosphine (L2), Ph2P(CH2)nPPh2, (n = 1, dppm; 2, dppe
and 3, dppp), Ph2P(S)(CH2)P(S)Ph2 (dppmS2) or
Ph2P(O)(CH2)2P(O)Ph2 (dppeO2) afforded mixed ligand
complexes [Pd(j1-Sac-CH2O)2(L2)], while reaction with
two equivalents of Ph3P, Ph3PO or Ph3PS (L) gave trans-
[Pd(j1-Sac-CH2O)2(L)2]. The N-hydroxymethylsacchari-
nate anion acts as a monodentate ligand, coordinating to
the palladium center through the hydroxymethyl oxygen
atom. The complexes were characterized by physico-
chemical and spectroscopic methods. In addition, the free
ligand N-hydroxymethylsaccharin and some of the com-
plexes were screened in vitro for antibacterial activity.
studied over the years [1–14]. Although for many years it
was a suspected carcinogen in rats [15, 16], in the 1990s it
was removed from the list of potential human carcinogens
[17]. Palladium and platinum saccharinate complexes
[7–14] have attracted interest primarily because of their
biological properties. Complexes of saccharine derivatives
have not been well studied; however, there is a recent
report on the synthesis of N-substituted saccharine
derivatives and their biological activity with respect to
selective inhibition of human carbonic anhydrase [18].
In continuation of our recent studies with Pd(II) com-
plexes [7, 19–21], herein we describe the preparation of
mixed-ligand saccharinate derivative complexes with
phosphines as co-ligands. N-hydroxymethylsaccharin (Sac-
CH2OH) was readily prepared (Scheme 1) and its reactions
with Na2PdCl4 and phosphines gave rise to the complexes
[Pd(j1-Sac-CH2O)2(L)n] (n = 1 or 2) in high yields. These
complexes were characterized by spectroscopic methods.
In addition, the phosphine derivative complexes were
screened for activity against several bacterial strains and
showed some antibacterial effects compared with the par-
ent compound.
Introduction
Saccharin (1,2-benzoisothiazol-3(2H)-one-1,1-dioxide or
o-benzosulfimide, Hsac) is known as a noncaloric artificial
sweetener. Its coordination chemistry has been extensively
Experimental
& Subhi A. Al-Jibori
subhi_aljibori@yahoo.com
Materials and methods
1
Department of Chemistry, College of Science, University of
Tikrit, Tikrit, Iraq
All chemicals and solvents used in this work were com-
mercial products and were used without further purifica-
tion. N-hydroxymethylsaccharin was synthesized according
to the literature method [22]. IR spectra were recorded in
the 4000–200 cm-1 range on a Bruker Tensor 28 spec-
trometer with a Platinum ATR unit. Melting points were
measured on an Electrothermal 9300 melting point
2
Department of Chemistry, College of Veterinary Medicine,
University of Tikrit, Tikrit, Iraq
3
Department of Chemistry, University College London, 20
Gordon Street, London WC1H 0AJ, UK
4
¨
Institut fu¨r Chemie, Martin-Luther-Universitat, Halle-
Wittenberg, Kurt-Mothes-Str. 2, 06120 Halle, Germany
123

Transition Met Chem
O
C
Preparation of complex 1
O
4
3
2
OH
CH2O
C
S
5
6
NH
O
N CH2
A warm solution of Sac-CH2OH (0.145 g, 0.68 mmol) in
EtOH (10 ml) containing a few drops of Et3N was added to
a solution of Na2PdCl4 (0.10 g, 0.34 mmol) in EtOH
(15 ml). The mixture was stirred for 15 min at room tem-
perature. The brown-yellow precipitate was filtered off,
washed with ethanol and dried under vacuum to afford
[Pd(j2-Sac-CH2O)2]Á2H2O (1) (Scheme 2). Brown yellow
solid. Yield: 0.13 g (68 %). Anal. Calc. for C16H16N2O10-
PdS2: C, 33.9; H, 2.8; N, 4.9; Found, C, 34.1; H, 2.9; N,
5.0 %. IR (KBr): 3521 t(O–H) for H2O; 3087 t(=C–H);
2985 t(C–H); 1673 t(C=O); 1593 t(C=C); 1294 tasy(SO2):
1174 tsy(SO2); 540 t(Pd–O) cm-1. 1H NMR (d6-DMSO): d
7.69 (d, 2H, 3J(HH) = 8.6 Hz, H1); 7.54 (t, 2H,
3J(HH) = 7.9 Hz, H2); 7.30 (d, 2H, 3J(HH) = 8.63 Hz,
H4); 6.97 (t, 2H, 3J(HH) = 7.8 Hz, H3); 5.25 (s, 4H,
OCH2). 13C NMR (d6-DMSO): d 171.60 (CO), 140.70,
136.11, 133.64, 126.03, 122.89, 61.39 (CH2). Melting
point: 180 °C (decomposes).
1
S
Reflux 1 h
8
7
O
O
O
Scheme 1 Preparation of Sac-CH2OH
apparatus. Elemental analysis was carried out on a CHN
analyzer type 1106 Carlo-Erba. The 1H and 13C NMR
spectra were recorded on Varian unity 400 and Gemini 200
spectrometers, respectively, with d6-DMSO as solvent. 31
P
NMR spectra were recorded on a Gemini 200 spectrometer
with d6-DMSO and CDCl3 as solvents and H3PO4 (85 %)
as an external reference. The NMR spectra are reported in
ppm. The NMR spectra and elemental analysis were car-
ried out at Al-Bayt University-Jordan and Institute fur
Anorganische Chemie, Martin-Luther-Universitat, Halle,
Germany. N-hydroxymethylsaccharin (Sac-CH2OH) was
characterized as follows. White prisms. Anal. Calc. for
C8H7NO4S; C, 45.1; H, 3.3; N, 6.6, Found: C, 45.1; H, 3.4;
N, 6.8 %. IR (KBr): 3290 m t(O–H); 3093 t(C–H); 2975
t(C–H); 1747 t(C=O); 1595 t(C=C); 1458 t(C–N); 1340
1
t
asy(SO2); 1184 tsy(SO2) cm-1. H NMR (d6-DMSO): d
Preparation of complex 2
8.28 (dd, 1H, H4, 3J(HH) = 7.8 Hz, Ph); 8.12 (dd, 1H, H7,
3J(HH) = 7.8 Hz, Ph); 8.05 (td, 1H, H5, 3J(HH) = 8.8 Hz,
4J(HH) = 1.2 Hz, Ph); 7.99 (td, 1H, 3J(HH) = 8.4 Hz,
4J(HH) = 1.3 Hz, H6); 6.74 (bs, 1H, OH); 5.18 (s, 2H,
OCH2). 13C NMR (d6-DMSO): d 161.49 (CO), 140.21 (C3,
Ph), 136.09 (C8, Ph), 134.51 (Ph), 129.19 (Ph), 125.09
(Ph), 121.99 (Ph), 68.51 (CH2). Melting point: 134–136 °C
(lit. 135–137) [22]. For antibacterial studies, the test
organisms were grown on nutrient agar medium in petri
plates [23–26]. Fresh solutions of the compounds were
prepared in DMSO and used to soak filter paper disks of
5 mm diameter and 1 mm thickness. The disks were placed
on previously seeded plates and then incubated at 37 °C,
and the diameter of the inhibition zone around each disk
was measured after 24 h (Table 1).
A solution of dppm (0.131 g, 0.34 mmol) in CHCl3
(10 ml) was added to a suspension of complex 1 (0.145 g,
0.34 mmol) in CHCl3 (15 ml). The resulting yellow solu-
tion formed was stirred at 30 °C for 3 h and then left for
slow evaporation at room temperature. The yellow pre-
cipitate was filtered off, washed with CHCl3 and dried
under vacuum (Scheme 3). The related complexes
[Pd(Sac-CH2O)2(dppe)] (3), [Pd(Sac-CH2O)2(dppp)] (4),
[Pd(Sac-CH2O)2(dppmS2)] (5) and [Pd(Sac-CH2O)2(-
dppeO2)] (6) were prepared and isolated in a similar
manner.
[Pd(Sac-CH2O)2(dppm)] (2): Yellow solid. Yield:
0.236 g (76 %). Anal. Calc. for C41H34N2O8P2PdS2, C,
53.8; H, 3.7; N, 3.1; Found, C, 53.6; H, 3.9; N, 3.0 %. IR
(KBr): 3546, 3454 t(O–H) for H2O; 3056 t(=C–H); 2997
t(C–H); 1695 t(C=O); 1587 t(C=C); 1294 tasy(SO2); 1164
1
tsy(SO2); 503 t(P–C); 530 t(Pd–O) cm-1. H NMR (d6-
Table 1 A diameter of inhibition zone (mm) of 100 lg/ml of free
Sac-CH2OH and its complexes
DMSO): d 8.46–7.37 (m, 28H, Ar), 5.06 (s, 4H, OCH2),
2.95 (s, 2H, CH2). 13C NMR (d6-DMSO): d 163.78, 140.70,
136.11, 133.64, 130.58, 126.88, 122.89, 63.76. 31P NMR
(d6-DMSO): d 29.37. Melting point: 196–199 °C.
Compound
Bacterial species
E. coli
B. subtilis
P. aeruginosa
S. aureus
[Pd(Sac-CH2O)2(dppe)] (3): Yellow solid. Yield: 84 %.
Anal. Calc. for C42H36N2O8P2PdS2, C, 54.3; H, 3.9; N, 3.0;
Found, C, 54.4; H, 3.8; N, 3.13 %. IR (KBr): 3064 t(=C–
H); 2929 t(C–H); 1699 t(C=O); 1585 t(C=C); 1292
Sac-CH2OH
23
19
35
65
10
27
43
05
05
75
20
34
05
50
05
05
[100
50
1
2
07
35
3
43
25
t
asy(SO2); 1143 tsy(SO2); 507 t(P–C); 530 t(Pd–O) cm-1
.
6
[100
10
20
1H NMR (d6-DMSO): d 7.27–7.66 (m, 28H, Ar), 5.17 (s,
4H, OCH2), 3.02 (t, 4H, 3J(HH) = 7.9 Hz, CH2). 13C
NMR (d6-DMSO): d 161.89, 140.89, 136.11, 132.89,
Ofloxacin
Ciprofloxacin
05
05
05
123

Transition Met Chem
Scheme 2 Preparation of
complex 1
O
OH
C
S
Et3N / EtOH
stirring 15 min.
O
C
O
2
O
N CH2
S
+ Na2PdCl4
CH2
N
N
.
2H2O
Pd
O
O
H2C
O
O
S
O
O
C
O
(1)
Scheme 3 Preparation of
complexes 2–9
O
C
N
CH2
O
P
P / CHCl3
S
P
P
O
O
Stirring 3 h
Pd
O
O
C
CH2
N
S
O
O
C
O
O
S
CH2
N
O
2H2O
Pd
O
O
N
H2C
S
O
O
C
O
O
C
N
S
H2C
O
O
O
L
+ 2L
/ CHCl3
Pd
Stirring 2 h
O
O
L
CH2
O
S
N
C
O
P
P = dppm (2); dppe (3); dppp (4); dppmS2 (5) or dppeO2 (6)
L= PPh3 (7); O=PPh3 (8); S=PPh3 (9)
130.58, 126.93, 122.89, 63.76. 31P NMR (d6-DMSO): d
44.46. Melting point: 204–208 °C (decomposes).
62.13. 31P NMR (d6-DMSO): d 24.47. Melting point:
268–272 °C (decomposes).
[Pd(Sac-CH2O)2(dppp)] (4): Yellow solid. Yield: 80 %.
Anal. Calc. for C45H44N2O9P2PdS2, C, 54.6; H, 4.5; N, 2.8;
Found, C, 54.3; H, 4.2; N, 3.0 %. IR (KBr): 3083 t(=C–H);
2987 t(C–H); 1701 t(C=O); 1591 t(C=C); 1302 tasy(SO2);
[Pd(Sac-CH2O)2(dppeO2)] (6): Yellow solid. Yield:
81 %. Anal. Calc. for C42H36N2O10P2PdS2: C, 52.5; H, 3.8;
N, 2.9; Found, C, 52.6; H, 3.6; N, 3.1 %. IR (KBr): 3100
t(=C–H), 2981 t(C–H), 1691 t(C=O), 1587 t(C=C), 1296
1
1143 tsy(SO2); 480 t(P–C); 526 t(Pd–O) cm-1. H NMR
t .
asy(SO2), 1163 tsy(SO2), 500 t(P–C), 526 t(Pd–O) cm-1
(d6-DMSO): d 8.28–7.96 (m, 28H, Ar); 5.18 (s, 4H,
1H NMR (d6-DMSO): d 7.12–7.71 (m, 28H, Ar), 5.04 (s,
4H, OCH2), 3.08 (t, 4H, 3J(HH) = 8.0 Hz, CH2). 13C
NMR (d6-DMSO): d 162.67, 141.09, 135.89, 132.83,
131.06, 125.87, 123.67, 61.45. 31P NMR (d6-DMSO): d
35.48. Melting point: 244–246 °C (decomposes).
3
OCH2); 2.88 (t, 4H, J(HH) = 8.1 Hz, CH2); 1.90 (b, 2H,
CH2). 13C NMR (d6-DMSO): d 164.0, 140.10, 135.36,
132.95, 131.13, 128.40, 122.56, 61.95. 31P NMR (d6-
DMSO): d 27.67. Melting point: 158–161 °C.
[Pd(Sac-CH2O)2(dppmS2)] (5): Yellow solid. Yield:
41 %. Anal. Calc. for C66H56N2O8P4PdS6, C, 55.5; H, 3.9;
N, 1.9. Found: C, 55.9; H, 4.2; N, 2.2 %. IR (KBr): 3053
t(C–H); 2918 t(C–H); 1703 t(C=O); 1529 t(C=C); 1290
Preparation of complex 7
A solution of PPh3 (0.178 g, 0.68 mmol) in CHCl3 (10 ml)
was added to a suspension of complex 1 (0.193 g,
0.34 mmol) in CHCl3 (15 ml) with stirring. The yellow
solution so formed was stirred at room temperature for 2 h,
then left to evaporate at room temperature. The yellow
t
asy(SO2); 1126 tsy(SO2); 499 t(P–C); 545 t(Pd–O) cm-1
.
1H NMR (CDCl3): d 7.10–8.01 (m, 28H, Ar), 5.20 (bs, 4H,
OCH2), 1.71 (s, 2H, CH2) ppm. 13C NMR (d6-DMSO): d
162.23, 140.47, 136.0, 132.65, 131.07, 126.98, 122.33,
123

Transition Met Chem
precipitate was filtered off, washed with diethyl ether fol-
lowed by CHCl3 and dried under vacuum (Scheme 3). The
complexes [Pd(Sac-CH2O)2(O=PPh3)2] (8) and [Pd(Sac-
CH2O)2(S=PPh3)2] (9) were prepared and isolated by
similar procedures.
t(C=O) at 1673 cm-1. The reaction of sac derivative
complex (1) with different diphosphines in an equivalent
ratio afforded [Pd(j1-Sac-CH2O)2(L2)] (2–6) in 60–85 %
yields, as illustrated in Scheme 3. The same reaction with
monophosphines gives rise to trans-[Pd(j1-Sac-CH2O)2
(L)2] (7–9) as yellow solids in 70–80 % yields. The Sac-
CH2O- in complexes 2–9 behaves as a monodentate ligand
coordinated through the oxygen atom of the CH2O- group.
This was deduced from the high frequency shift of t(C=O)
from 1673 cm-1 for complex 1 to 1691–1701 cm-1 in the
spectra of complexes 2–9. Complexes 1–9 are stable in
DMSO or DMF solutions when kept at room temperature
and showed no decomposition over a week as evident from
[Pd(Sac-CH2O)2(PPh3)2] (7): Yellow solid. Yield:
0.32 g (76 %). Anal. Calc. for C52H42N2O8P2PdS2: C,
59.2; H, 4.0; N, 2.6; Found, C, 59.4; H, 4.2; N, 2.4 %. IR
(KBr): 3091 t(=C–H); 2972 t(C–H); 1692 t(C=O); 1571
t(C=C); 1290 tasy(SO2; 1155 tsy(SO2); 522 t(P–C); 533
t(Pd–O) cm-1 1H NMR (d6-DMSO): d 8.28–7.09 (m,
.
38H, Ar), 5.09 (s, 4H, OCH2). 13C NMR (d6-DMSO): d
163.60, 140.70, 136.11, 132.98, 130.58, 125.76, 122.89,
62.65. 31P NMR (d6-DMSO): d 18.05. Melting point:
254–259 °C (decomposes).
1
their H NMR spectra. However, they are unstable in hot
DMSO or DMF solution, decomposing to black
precipitates.
[Pd(Sac-CH2O)2(O=PPh3)2] (8): Brown-yellow. Yield:
81 %. Anal. Calc. for C52H42N2O10P2PdS2: C, 57.4; H, 3.9;
N, 2.6; Found, C, 57.5; H, 3.9; N, 2.7 %. IR (KBr): 3093
t(C–H); 2933 t(C–H); 1696 t(C=O); 1604 t(C=C); 1288
In order to determine the precise coordination sphere,
we attempted to grow X-ray quality single crystals of these
complexes by dissolving them in DMSO or DMF at room
temperature with the addition of a few drops of EtOH or
CHCl3. Unfortunately all these attempts were unsuccessful
and no crystals suitable for X-ray diffraction studies were
obtained.
t
asy(SO2); 1157 tsy(SO2); 522 t(P–C); 546 t(Pd–O) cm-1
.
1H NMR (d6-DMSO): d 8.06–7.05 (m, 38H, Ar), 5.73 (s,
4H, OCH2). 13C NMR (d6-DMSO): d 163.93, 140.04,
136.49, 132.79, 130.94, 125.64, 121.92, 64.37. 31P NMR
(d6-DMSO): d 43.23. Melting point: 189–192 °C.
Spectroscopic and analytical data are in full accordance
1
with the proposed formulations. The H NMR spectra of
[Pd(Sac-CH2O)2(S=PPh3)2] (9): Dark yellow. Yield:
76 %. Anal. Calc. for C52H42N2O10P2PdS4: C, 55.8; H, 3.8;
N, 2.5; Found, C, 55.8; H, 3.9; N, 2.7 %. IR (KBr): 3087
t(C–H); 2873 t(C–H); 1698 t(C=O); 1612 t(C=C); 1292
each complex displayed the expected signals for the sac-
charinate derivative as well as the phosphine ligands. The
single peak observed in their 31P NMR spectra confirmed
symmetric coordination around the metal center in these
complexes. The N-hydroxymethylsaccharinate anion
coordinated to the palladium(II) center through hydrox-
ymethyl oxygen in each of these complexes most likely in a
square planar geometry.
t
asy(SO2); 1151 tsy(SO2); 503 t(P–C); 542 t(Pd–O) cm-1
.
1H NMR (d6-DMSO): d 7.97–6.99 (m, 38H, Ar), 5.24 (s,
4H, OCH2). 13C NMR (d6-DMSO): d 163.12, 141.11,
136.52, 132.79, 131.94, 125.68, 121.33, 64.56, 41.17. 31P
NMR (d6-DMSO): d 17.44. Melting point: 260–262 °C
(decomposes).
Antibacterial activities
Results and discussion
Antibacterial activities of the free ligand and its complexes
were tested in vitro against the bacterial species Escher-
ichia coli, Bacillus subtilis, Pseudomonas aeruginosa and
Staphylococcus aureus.
In order to prepare the target phosphine derivative com-
plexes, [Pd(j1-Sac-CH2O)2(L)n] (n = 1, 2), we first pre-
pared the saccharine derivative complex with
palladium(II). Thus, treatment of Na2[PdCl4] with two
equivalents of N-hydroxymethylsaccharin (Sac-CH2OH) in
the presence of NEt3 afforded trans-[Pd(j2-Sac-CH2O)2]
(1) in EtOH (Scheme 2). The parent Pd(II) complex was
assigned as the trans isomer based primarily on its IR
spectrum, which is relatively simple in accordance with the
higher symmetry and also with other complexes of the type
trans-[Pd(j1-Sac-CH2O)2(L)2] (see below). The hydrox-
ymethylsaccharinate anion in complex 1 behaves as a
bidentate ligand, coordinating through the carbonyl and
CH2O oxygen atoms. Evidence for this assignment comes
from the IR spectrum of complex 1 which displayed
The results of the antibacterial studies are summarized
in Table 1. The standard error for the experiment was
0.002 lg/ml, and the experiments were repeated three
times under similar conditions. DMSO was used as nega-
tive control, and ofloxacin and ciprofloxacin were used as
positive controls. The results show that the metal chelates
are more active than the starting materials and the free
ligand, as is frequently the case [26]. The Sac-CH2OH
ligand shows good activity against the bacterial strain
E. coli and B. subtilis, while all the complexes exhibit
excellent in vitro antibacterial activities against both Gram-
positive and Gram-negative organisms.
123

Transition Met Chem
9. Guney E, Yilmaz VT, Ari F, Buyukgungor O, Ulukaya E (2011)
Polyhedron 30:114
Conclusions
10. Guney E, Yilmaz VT, Buyukgungor O (2010) Inorg Chim Acta
363:2416
11. Guney E, Kaya Y, Yilmaz VT, Gumus S (2011) Spectrochim
Acta Part A 79:1171
12. Guney E, Yilmaz VT, Buyukgungor O (2011) Polyhedron
30:1968
13. Henderson W, Nicholson BK, McCaffrey LJ (1999) Inorg Chim
Acta 285:145
14. Henderson W, Nicholson BK, Chung DC, Crystallogr Acta
(2002) Sect E 58:m432
15. Price JM, Biava CG, Oser BL, Vogin EE, Steinfeld J, Ley HL
(1970) Science 167:1131
16. Weihrauch MR, Diehl V, Bohlen H (2001) Mediz Klin 96:670
17. Chappel CI (1992) Reg Toxicol Pharm 15:253
18. Ascenzio MD, Carradori S, Monte CD, Secci D, Ceruso M,
Supuran Claudiu T (2014) Bioorg. Med Chem 22:1821
19. Al-Jibori SA, Al-Nassiry AIA, Hogarth G, Salassa L (2013) Inorg
Chim Acta 398:46
This work has shown that the synthesis of sac derivative
complexes of the type [Pd(Sac-CH2O)2(L)n] containing
various phosphine ligands is general and straightforward
starting from Na2[PdCl4] and readily prepared ligands.
Further, the yields of each step are high, reactions can be
carried out in air and product isolation is simple. However,
crystallization of the synthesized complexes proved to be
intractable. The complexes showed some antibacterial
activities. Further syntheses of other transition metal
complexes with this ligand are in progress.
Acknowledgments We thank Department of Microbiology, College
of Veterinary Medicine, Tikrit University for the antibacterial study
and Erasmus Mundus programme for a post-doctoral scholarship to S.
B.-M.
20. Al-Jibori SA, Al-Jibori QKA, Schmidt H, Merzweiler K, Wagner
C, Hogarth G (2013) Inorg Chim Acta 402:69
21. Al-Jibori SA, Al-Nassiry RAQ, Al-Jibori GHH, Merzweiler K,
Wagner C, Schmidt H, Basak-Modi S, Hogarth G (2014) Trans
Met Chem 39:735
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