Metal complexes of 4-amino-N-(2-pyrimidinyl)benzene sulfonamide: Synthesis, characterization and antiprotozoal studies

Article abstract of DOI:10.1080/15533170701608957

We present the synthesis, characterization and in vitro antiprotozoal studies of Cu(II), Zn(II), Mn(II), Ni(II), Pd(II), Pt(II), and VO(II) complexes of sulfadiazine. Elemental analysis, IR, UV-Vis, room temperature magnetic moments were used to characterize the complexes. Cu(II), Zn(II), Mn(II), Ni(II), and VO(II) formed octahedral complexes formulated as [M(SD)2(H2O)2]xH2O, (SD=sulfadiazine), while Pd(II) and Pt(II) formed square planar complexes containing one molecule of sulfadiazine. In all the complexes, the sulfadiazine acts as a bidentate ligand coordinating through the sulfonamido N-atom and the pyrimidinic N-atom. The complexes were screened against the resistant strains of Plasmodium falciparum, T. b. rhodosiense and L. donovani to determine their antiprotozoal activities.

Full text of DOI:10.1080/15533170701608957

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Metal Complexes of 4‐Amino‐N‐(2‐pyrimidinyl)benzene
Sulfonamide: Synthesis, Characterization and
Antiprotozoal Studies
Peter A. Ajibade a , Gabriel A. Kolawole b & Paul O'Brien c
a Department of Chemistry , University of Fort Hare , South Africa
b Chemistry Department , University of Zululand , Kwadlangezwa, South Africa
c School of Chemistry , The University of Manchester , Manchester, UK
Published online: 02 Oct 2007.
To cite this article: Peter A. Ajibade , Gabriel A. Kolawole & Paul O'Brien (2007) Metal Complexes of
4‐Amino‐N‐(2‐pyrimidinyl)benzene Sulfonamide: Synthesis, Characterization and Antiprotozoal Studies, Synthesis and
Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 37:8, 653-659
To link to this article: http://dx.doi.org/10.1080/15533170701608957
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 37:653–659, 2007
Copyright # 2007 Taylor & Francis Group, LLC
ISSN: 1553-3174 print/1553-3182 online
DOI: 10.1080/15533170701608957
Metal Complexes of 4-Amino-N-(2-pyrimidinyl)benzene
Sulfonamide: Synthesis, Characterization and Antiprotozoal
Studies
Peter A. Ajibade
Department of Chemistry, University of Fort Hare, South Africa
Gabriel A. Kolawole
Chemistry Department, University of Zululand, Kwadlangezwa, South Africa
Paul O’Brien
School of Chemistry, The University of Manchester, Manchester, UK
eradicate or control malaria, the disease remains a major and
We present the synthesis, characterization and in vitro anti- growing threat to public health and economic development of
protozoal studies of Cu(II), Zn(II), Mn(II), Ni(II), Pd(II), Pt(II),
and VO(II) complexes of sulfadiazine. Elemental analysis,
countries in the tropical and sub-tropical regions of the
world. It infects about 300–500 million people each year and
causes up to 2.7 million deaths and 42 million Disability
IR, UV-Vis, room temperature magnetic moments were used
to characterize the complexes. Cu(II), Zn(II), Mn(II), Ni(II),
Adjusted Life Years (Daly’s) annually.[2] The mortality
[M(SD)2(H2O)2] xH2O, (SD 5 sulfadiazine), while Pd(II) and levels are greatest in sub-Saharan Africa, where children
and VO(II) formed octahedral complexes formulated as
.
Pt(II) formed square planar complexes containing one molecule
of sulfadiazine. In all the complexes, the sulfadiazine acts as a
under 5 years of age account for 90% of all deaths due to
malaria.[3,4] The frightening spread of the parasitic resistance
has led the World Heath Organization to predict that without
new anti-malarial drug intervention, the number of cases of
bidentate ligand coordinating through the sulfonamido N-atom
and the pyrimidinic N-atom. The complexes were screened
against the resistant strains of Plasmodium falciparum, T. b. rhodo-
siense and L. donovani to determine their antiprotozoal activities. malaria will have doubled by the year 2010.[5] The emergence
and spreading of parasites resistant to anti-malarial drugs cur-
rently in use indicates that novel compounds need to be devel-
oped by identification of novel chemotherapeutic targets.[6]
Keywords sulfadiazine, metal complexes, antiprotozoal, Plasmo-
dium falciparum, malaria, sleeping sickness
Hence, the search for new anti-malarial therapies is a high
priority for the control of the disease.
The use of metal complexes as pharmaceuticals has shown
promise in recent years particularly as anticancer agents[7,8] as
INTRODUCTION
Malaria is one of the three major infectious diseases
ravaging the world; the others are tuberculosis and AIDS.[1]
Malaria was successfully reduced and erroneously believed it
could be eradicated after the World War II due to easy
access to cheap insecticides and readily available drugs like
chloroquinine. Despite more than a century of efforts to
well as gadolinium complexes used as contrast agents for
magnetic resonance imaging.[9] Other fields of research
include arthritis[10] and cardiovascular medicine. In the
search for novel drugs against chloroquinine-resistant malaria
parasites, the modification of existing drugs by coordination
to metal centres has attracted considerable attention.[11–16]
Interest in the metal complexes of sulfadiazine is due to its
use in pharmaceuticals. Zinc sulfadiazine is used to prevent
bacterial infection in burnt animals and silvadene (2-sulfadi-
azinilamido-silver (I)) is used commercially for the treatment
of topical burn.[17] The crystal structures of silver sulfadia-
zine,[18] zinc sulfadiazine[19] and cadmium sulfadiazine[20]
have been reported. At present, there is still no conclusive
proof as to the preferred site of coordination for any particular
metal ion to the sulfadiazine. Coordination can occur via any of
Received 23 April 2007; accepted 1 June 2007.
The authors wish to thank Prof. Reto Brun and Marcel Kaizer
(Swiss Tropical Institute) for the biological screening, and the
National Research Foundation (South Africa) and the Royal Society
(UK) for financial support. PAA thanks the University of Ado-Ekiti,
Nigeria, for study leave.
Address correspondence to Gabriel A. Kolawole, Chemistry
Department, University of Zululand, Private Bag X1001, Kwadlan-
gezwa 3886, South Africa. E-mail: gayokola@pan.uzulu.ac.za
653

654
P. A. AJIBADE ET AL.
the available sites. In our effort to contribute to studies in Synthesis of Manganese (II) Complex of Sulfadiazine
metal-based drug as alternative therapy in the management
of chloroquine-resistant malaria, we have embarked on the syn-
thesis, characterization and in vitro studies of metal complexes
of antimalarial drugs. Recently we reported the single crystal
X-ray structure of sulfadiazine and its Co(II) complex.[21] In
the present study, we present the synthesis, characterization
and in vitro studies of Cu(II), Zn(II), Mn(II), Ni(II), Pd(II),
Pt(II), and VO(II) complexes of sulfadiazine.
First, 2.723 g (10 mmol) sodium salt of sulfadiazine was
dissolved in 50 mL of deionised water followed by the
.
addition of 0.990 g (5 mmol) of MnCl2 4H2O in 30 mL of
deionised water. The mixture was stirred for about 3 h at
408C and the cream-coloured solution was cooled to room
temperature and filtered under vacuum, washed with water
and dried over CaCl2. The complex is formulated as
[Mn(SD)2(H2O)2]; yield 64%.
Synthesis of Nickel (II) complex of sulfadiazine
EXPERIMENTAL
.
First, 1.1886 g (5 mmol) of NiCl2 6H2O was dissolved in
15 mL of deionised water followed by a slow addition of
2.723 g (10 mmol) of sodium salt of sulfadiazine in 50 mL of
deionised water. The mixture was stirred at 408C for 3 h. The
green product was filtered under vacuum, washed twice with
water and dried over CaCl2. The complex is formulated as
Chemicals and Instrumentation
All solvents and chemicals were of analytical grade and
used without further purification. Elemental analyses were per-
formed at the Microanalytical Laboratory of the School of
Chemistry, The University of Manchester, UK. FTIR spectra
were obtained on a Perkin-Elmer Paragon 1000 FTIR spectro-
photometer in the range 4000–250 cm21. UV-Vis spectra were
obtained on a Perkin-Elmer Lambda 20 spectrophotometer
equipped with an integrating sphere for diffuse reflectance
spectra. The solution spectra were on DMF solutions. Room
temperature magnetic susceptibility measurements were
carried out using Sherwood scientific magnetic susceptibility
balance using Hg[Co(SCN)4] as the calibrant. Diamagnetic
corrections were estimated from Pascal’s constants.[22]
.
[Ni(SD)2(H2O)2] 2H2O; yield 78%.
Synthesis of Palladium (II) Complex of Sulfadiazine
First, 0.571 g (1.75 mmol) of K2PdCl4 was dissolved in
10 mL of deionised water followed by slow addition of
0.953 g (3.5 mmol) of sodium salt of sulfadiazine in 40 mL
of methanol. The mixture was stirred at 408C for 3 h. The
brown product was filtered under vacuum washed twice with
water and dried over CaCl2. The complex is formulated as
[Pd(SD)Cl(CH3OH)]; yield 56%.
Synthesis of Platinum(II) Complex of sulfadiazine
First, 0.726 g (1.75 mmol) of K2PtCl4 was dissolved in
minimum amount of deionised water followed by slow
addition of 0.953 g (3.5 mmol) of sodium salt of sulfadiazine
in 40 mL methanol. The mixture was stirred at 408C for 3 h.
The yellow product was filtered under vacuum, washed twice
with water and dried over CaCl2. The complex is formulated
as [Pt(SD)(H2O)(Cl)]; yield 53%.
SYNTHESIS OF THE COMPLEXES
Synthesis of Copper(II) Complexes of Sulfadiazine
The copper complexes were made from CuCl2 2H2O
.
(0.852 g, 5 mmol), CuSO4 5H2O (1.248 g, 5 mmol), or Cu2
.
.
(CH3COO)4 2H2O (1.269 g, 5 mmol). The complexes were
prepared by dissolving 2.723 g (10 mmol) of sodium salt of
sulfadiazine in 50 mL of deionised water or methanol
followed by a dropwise addition of each of the copper salts.
The brown solution obtained in each case was stirred continu-
ously at about 408C for 3 h. Each solution was cooled to room
temperature and filtered under vacuum and washed with either
water or methanol. The yield was about 80–89% and the same
complex, formulated as [Cu(SD)2(H2O)2], was obtained irres-
pective of the starting metal salt.
Synthesis of Oxovanadium (IV) Complex of Sulfadiazine
.
First, 1.310 g (5 mmol) of VOSO4 5H2O was dissolved in
15 mL of deionised water followed by a slow addition of
2.723 g (10 mmol) of sodium salt of sulfadiazine in 50 mL of
deionised water. The mixture was stirred at 408C for 1 h. The
product was filtered under vacuum, washed twice with water
and dried over CaCl2. The complex is formulated as
.
[VO(SD)2(H2O)] H2O; yield 68%.
Synthesis of Zinc (II) Complexes of Sulfadiazine
The zinc complexes were made by dropwise addition of
BIOLOGICAL TESTS
The tests were performed as microplate assays using
.
5 mmol of ZnCl2 6H2O (1.222 g) or Zn(CH3COO)2 4H2O
.
(1.278 g) in 30 mL of deionised water to a solution containing T. b. rhodosiense (STIB 900), L. donovani (MHOM-ET-67/
2.723 g (10 mmol) of sodium salt of sulfadiazine in 50 mL of L82) and K1 strain of P. falciparum (resistant to chloroquine
water. The solution was stirred at about 408C for 3 h, cooled and pyrimethamine). In vitro activity against erythrocytic
3
to room temperature, filtered under vacuum, washed with stages of P. falciparum was determined using the H-hypox-
water and dried over CaCl2. The complex is formulated as anthine incorporation assay.[23] Cytotoxicity was assessed
[Zn(SD)2(H2O)2]; yield 87%.
with rat skeletal myoblast (L-6 cells) with the same assay

SYNTHESES OF METAL COMPLEXES OF SULFADIAZINE
655
that was used for the determination of the antitrypanosomal
activity. A description of these assays was recently reported.[24]
The following substances were used as standard: melarsoprols
(T. b. rhodosiense), L. donovani (Miltefosine), and P. falciparum
(chloroquine).
RESULTS AND DISCUSSION
The formation of some of the metal complexes may be rep-
resented by the following general equation:
The syntheses were carried out using salts of different anions to
isolate metal complexes with different counterions but results
of the analyses showed that irrespective of the metal salt
used (chloride, nitrates, sulfate or acetate) the complex
formed was always the same. In forming the complex, the
metal ion coordinated via the sulfonamido N and pyrimidine
N of the sulfadiazine, solvent molecules occupied the other
coordination sites. The Pt(II) and Pd(II) isolated from
aqueous methanol mixture gave square planar complexes con-
sisting of one molecule of sulfadiazine, a chloride ion and the
fourth coordination sphere is occupied by a molecule of
methanol in the case of the Pd(II) and water in the Pt(II)
complex. The proposed formulation can be rationalised by
the equation presented here, and the proposed structures for
the complexes are shown in Figures 1–5.
FIG. 1. Proposed structures for the complexes.
The analytical data, melting point/decomposition temperatures
and room temperature magnetic moments of the complexes are
presented in Table 1.
observations confirm that the coordination of sulfadiazine to
the metal is through the sulfonamido N atom.
SPECTRAL AND MAGNETIC PROPERTIES
In the Cu(II) complex, multiple absorption bands in the
regions 3750–3500 cm21 can be attributed to the presence of
coordinated water. There are little changes in both the sym-
metric and asymmetric stretching frequencies of SO2
Infrared Spectra
The relevant infrared bands of the complexes are presented
in Table 2. The IR spectra of the free ligand and the metal com-
plexes were compared and assigned on the basis of careful
comparison. The bands in the region 3450–3000 cm21 due
to symmetrical and asymmetrical stretching modes of NH2 in
the spectrum of the ligand undergo only slight changes in the
spectra of the complexes.[25] These differences may be due to
the interaction between the free NH2 groups on sulfadiazine
and the stretching, wagging and rocking vibrations of coordi-
nated and/or lattice water, or due to intermolecular hydrogen
bonding. This is an indication that the NH2 groups on the
ligands are not involved in the coordination to the metal
ions. The effect of the coordinated metal is however noticeable
on the SO2 symmetrical and asymmetrical stretching modes
that are shifted to lower wavenumbers while the n(S-N)
shifted to higher wavenumbers in all the complexes. These
FIG. 2. Solution spectra of Ni(II) and Pt(II) sulfadiazine complexes.

656
P. A. AJIBADE ET AL.
donation is reduced, lowering the V55O bond order. As a
result the nV55O frequency will decrease. The VO2þ
frequencies generally fall in the range 960 + 50 cm21, In
this complex nV55O is assigned to the sharp band that
appear at 945 cm21, which appears to overlap with the n(SN)
observed in the other complexes. The lowering of nV55O in
this complex strengthens formulating the complex as having
coordination of one water molecule to the sixth position,
axial to V55O resulting in the weakening of the V55O
bond.[26] The V-N is assigned to bands at 550 and 511 cm21
The bands in the range 790–844 cm21 and 510–580 cm21
.
,
FIG. 3. Solution spectrum of VO(II) sulfadiazine complex in DMF.
observed in all the complexes, are assigned to the wagging and
rocking vibrations of coordinated water respectively.
indicating that the SO2 did not coordinate. The nS-N shifted in
the complex as observed in the Co(II) sulfadiazine com-
plexes.[21] The bands at 578 and 526 cm21 are assigned to
Cu-N and the band at 412 cm21 is assigned to the Cu-O.
The Mn-N and Mn-O vibrations are assigned to bands at 345
and 278 cm21, respectively while that of n(Zn-N) bands and the
n(Zn-O) are assigned at 388 cm21 and 288 cm21 respectively.
Other n(M-N) and n(M-O) frequencies are assigned at 378
and 345 cm21 (for Ni), 501 cm21 and 409 cm21 (for Pd),
and 512 cm21 and 423 cm21 (for Pt). The nPd-Cl and nPt-Cl
are assigned at 257 cm21 and 284 cm21, respectively.
Electronic Spectra and Magnetic Moments
The Cu(II) complex of sulfadiazine showed a broad asym-
metric band in the region 17,391–16,000 cm21 expected for
a d–d transition of an octahedral Cu(II) complex.[27] The
broadness of the band could be attributed to the overlapping
of several bands as a result of strong Jahn–Teller distortion
expected in a d9 ion.[28] A magnetic moment of 1.88 B. M. con-
firmed that the complex is monomeric.
The Ni(II) complex gave three bands (Fig. 2) corresponding
to the partially allowed electronic transitions for a d8 ion in an
octahedral environment.[27] A broad band that starts at about
The V55O bond in VO(II) complexes can be regarded as a
multiple covalent bond, the p component consisting of pp
electrons to oxygen of dp orbitals of vanadium. The
electron–accepting capacity of oxovanadium (IV) markedly
depends upon the ligands coordinated to the oxycation
moiety. Depending upon the donor ability of ligand, by increas-
ing the electron density in the metal, the O(pp) ! O(dp)
3
3
11,000 cm21 is assigned to T1g(F) ! T2g(F); a second
broad band that peaked at 15,773 cm21 is assigned to
3T1g(F) ! A2g(F), while another band appeared at
3
27,855 cm21 assigned to A2g(F) ! T1g(P).[29] The effective
magnetic moment of 2.98 B.M. obtained for the Ni(II) complex
confirmed the octahedral stereochemistry.
3
3
TABLE 1
Analytical data for the compounds
Elemental analyses (observed)
Formula
mass
Compounds
Empirical formula
CuC20H22N8S2O6
M.pt./8C
C
H
N
S
[Cu(SD)2(H2O)2]
598.11
217
40.56
(40.16)
39.85
3.37
(3.71)
3.45
18.78
(18.73)
18.25
10.68
(10.72)
10.74
(10.69)
10.96
(10.88)
10.27
(10.27)
7.65
[Zn(SD)2(H2O)2]
[Mn(SD)2(H2O)2]
ZnC20H22N8S2O6
MnC20H22N8S2O6
NiC20H26N8S2O8
PdClC11H13N4SO3
PtC10H11N4SO3Cl
VOC20H22N8O6S2
599.96
589.50
629.29
423.18
497.82
601.51
236
234
228
237
214
223
(40.04)
39.85
(3.70)
3.62
(18.68)
18.53
(40.75)
38.44
(3.76)
3.63
(19.01)
17.94
.
[Ni(SD)2(H2O)2] 2H2O
[Pd(SD)Cl(CH3OH)]
[Pt(SD)(H2O)(Cl)]
(38.17)
31.42
(4.16)
3.51
(17.81)
13.60
(31.22)
23.84
(3.10)
2.46
(13.24)
10.87
(7.58)
6.72
(24.13)
39.94
(40.16)
(2.23)
3.69
(3.56)
(11.25)
18.63
(18.45)
(6.44)
10.66
(10.24)
.
[VO(SD)2(H2O)] H2O

SYNTHESES OF METAL COMPLEXES OF SULFADIAZINE
657
TABLE 2
Selected IR data (cm21) for sulfadiazine and the complexes
Formulation
Sulfadiazine
n(NH2)
n(C55N)
n(SO2)asym
n(SO2)sym.
n(SN)
nMN
nMO
3422vs
3355vs
3448s
368s
1652vs
1325vs
1157vs
942s
[Cu(SD)2(H2O)2]
[Zn(SD)2(H2O)2]
[Mn(SD)2(H2O)2]
1631vs
1628s
1277ms
1126
971
526s
388s
345s
438s
378s
512s
511s
412s
288s
278s
308s
342w
423s
3423vs
3355vs
3454s
3176s
3460s
3369s
3342s
3322s
3417s
3318s
3422s
3039s
1325vs
1264ms
1326vs
1264s
1133s
1079s
1132s
977vs
946vs
944vs
970vs
968vs
945vsa
1654vs
1652vs
1630s
.
[Ni(SD)2(H2O)2] 2H2O
[Pd(SD)(H2O)(OCH3)]
[Pt(SD)(H2O)(Cl)]
1326vs
1262ms
1258ms
1155s
1090s
1124s
1631s
1260ms
1124s
1159s
.
[VO(SD)2(H2O)] H2O
1624vs
1324vs
1262vs
a
Abbreviations: v ¼ Very; s ¼ Strong; m ¼ Medium; w ¼ Weak. Assigned to n(V55O).
The solution spectrum of Mn(II) complex of sulfadiazine
The electronic spectra of VO(II) complexes are dominated
gave a horizontal line in the visible region and can thus be by square pyramidal geometry and characterised by three d-d
inferred that it is a high-spin Mn(II) octahedral complex.[27] transitions in the range 800–30,000 cm.21[32] The single
A magnetic moment of 5.86 B.M. obtained further confirmed band observed for the VO(II) sulfadiazine complex in the
the complex to be high spin and octahedral.
region of about 22,883 cm21 (Fig. 3) is indicative that the
Pd(II) and Pt(II) typically form square planar complexes complex is octahedral.[25] The band is assigned to b2 ! a1
with electronic spectra dominated by charge transfer transition. It could thus be concluded that the DMF most
bands.[29] Both complexes display very intense absorption probably forms an adduct with the complex or that the
bands in the range 38,460–22,220 cm21 that are clearly complex retains its solid-state octahedral structure in solution.
charge transfer in origin and associated with high spin-orbit
ꢀ
coupling.[30] This is accompanied by a broad shoulder at
Antiparasitic Screening
about 19,000 cm21 (Fig. 2). Magnetic moments of 0.24 B.M.
The antiplasmodial and antitrypanosomal activities of the
for the Pd(II) and 0.32 B.M. for Pt(II) confirmed that the com- complexes are presented in Table 3. In general, the Mn(II)
plexes are diamagnetic.
complex exhibit higher antiplasmodial activities than the
TABLE 3
In vitro activity of sulfadiazine and its metal complexes against P. falciparum strains
T. b.
rhodosiense
IC50 (mM)
P. falc. K1
IC50 (mM)
L. donovani
IC50 (mM)
Cytotoxicity
L6
Compounds
Sulfadiazine
[Cu(SD)2(H2O)2]
[Zn(SD)2(H2O)2]
.5
.5
.5
.5
2.127
.5
.5
0.009
19.9
.90
.90
.90
.90
.90
15.063
.90
.90
54.407
35.331
.90
.30
27.5
.30
7.2
.
[Ni(SD)2(H2O)2] H2O
[Mn(SD)2(H2O)2]
[Pd(SD)(H2O)(OCH3)]
Pt(SD)2(H2O)2Cl]
.30
.30

658
P. A. AJIBADE ET AL.
4. Breman, J. G. The ears of Hippopotamus: Manifestations,
determinants and estimates of the malaria burden. Am. J. Trop.
Med. Hyg. 2001, 64, 1–11.
other complexes and sulfadiazine. The complexes are,
however, highly toxic except the copper complex that exhib-
ited acceptable cytotoxicity of 19.9 mM. The Mn(II) complex
is about 2.4 times more active than sulfadiazine. Even
though the complexes are more toxic than sulfadiazine, they
are still less toxic than the widely used chloroquine
(IC50 ¼ 188.5 mM).[32] The Cu(II) and Mn(II) complexes are
candidates for further investigation.
5. Gallup, J. L.; Sadd, J. D. The economic burden of malaria. Am.
J. Trop. Med. Hyg. 2001, 64, 85–96.
6. Olliaro, P.; Cattani, J.; Wirth, D. Malaria, the submerged disease.
J. Am. Med. Assoc. 1996, 275, 230–233.
7. Lebwohl, D.; Canetta, R. Clinical development of platinum com-
plexes in cancer therapy: a historical perspective and an update.
Euro. J. Cancer 1998, 34 (10), 1522–1534.
The complexes were also evaluated against axenic L.
donovani amastigotes and the T. b. rhodosiense tripomasti-
gotes. The studied stages are the most relevant clinically of
their life cycle. Against L. donovani, the Zn(II) and Mn(II)
complexes showed inhibition of growth at the micromolar
level with the manganese complex being the most potent.
The complexes of Cu(II), Pd(II), and Mn(II) inhibit the
growth of T. b. rhodosiense at the micromolar range. The
Cu(II) complex is the most potent and least toxic. At present,
2 compounds used to treat East African sleeping sickness are
very toxic. The early stage of T. b. rhodosiense disease is
treated with the nephrotoxic drugs suramin.[33] The other drug
in use is melarsoprol that has been restricted to the late-stage
of sleeping sickness because of its fatality. The Cu(II)
complex that is most active is less active than suramin
(IC50 ¼ 0.0075 mM)[34] and melarsoprol (IC50 ¼ 0.0039 mM).
These complexes still need to be optimized to make them
more soluble in DMSO and probably in water.
8. Messori, L.; Abbate, F.; Marcon, G.; Orioli, P.; Fortani, M.;
Mini, E.; Mazzei, T.; Carotti, S.; O’connell, T.; Zanello, P.
Gold (III) complexes as potential antitumor agents: solution
chemistry and cytotoxic properties of some selected gold (III)
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elemental analyses, electronic and IR spectra. All the com-
plexes are air stable and insoluble in most common solvents.
They have octahedral or square planar coordination in which
the metal ions are coordinated to sulfadiazine molecules that
act as bidentate ligands and some water molecules. The
Ni(II) complex contains two lattice water molecules. The in
vitro antiprotozoal screening on the complexes showed that
they have comparable activity like sulfadiazine except the
Mn(II) complexes that is more active in vitro than sulfadiazine.
They are generally more toxic than sulfadiazine but less toxic
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