In vitro antitumour and antibacterial studies of some Pt(IV) dithiocarbamate complexes

Article abstract of DOI:10.1016/j.saa.2005.09.023

A few Pt(IV) complexes of the type [Pt(L)₂Cl₂] [where L = morpholine dithiocarbamate (L¹), aniline dithiocarbamate (L²), N-(methyl, cyclohexyl) dithiocarbamate (L³) and N-(ethyl, cyclohexyl) dithiocar

Full text of DOI:10.1016/j.saa.2005.09.023

Spectrochimica Acta Part A 65 (2006) 32–35
In vitro antitumour and antibacterial studies of some
Pt(IV) dithiocarbamate complexes
N. Manav, A.K. Mishra, N.K. Kaushik∗
Department of Chemistry, University of Delhi, Delhi 110007, India
Received 11 July 2005; accepted 3 September 2005
Abstract
AfewPt(IV)complexesofthetype[Pt(L)2Cl2][whereL = morpholinedithiocarbamate(L1), anilinedithiocarbamate(L2), N-(methyl, cyclohexyl)
dithiocarbamate (L3) and N-(ethyl, cyclohexyl) dithiocarbamate (L4)] were synthesized. The complexes have been characterized by elemental
1
analysis, molar conductance, IR, electronic, H and 13C NMR spectroscopic studies. The ligands found to act in monobasic bidentate fashion.
Cyclicvoltammetric studies, antibacterial and in vitro antitumour studies were also carried out.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Synthesis; Characterisation; Spectral; Antibacterial; Antitumour
1. Introduction
ization of platinum(IV) dithiocarbamates complexes including
in vitro antitumour and antibacterial study.
The clinical utility of platinum anticancer agents is well
proved [1–5]. However, the clinical usefulness of cisplatin has
been frequently limited by its severe side effects such as nephro-
toxicity, nausea, ototoxicity, neurotoxicity and myelotoxicity
[6] development of acquired resistance [7] low activity against
breast and colon cancer. Therefore, it is desirable to develop a
new platinum-based anticancer drug with broader spectrum of
activity, improved clinical efficacy and reduced toxicity, better
thancisplatin. The interestin dithiocarbamatecomplexesof plat-
inum has been stimulated because it was reported that dialkyl
dithiocarbamate when coadministered with cisplatin reduces its
nephrotoxicity [8–10]. A broad spectrum of preclinical antitu-
mour activity of platinum(IV) complexes have been reported
having a different mechanism from platinum(II) and remain
active against general cancer cell lines as well as other cell lines
resistant to cisplatin [11]. Moreover, metal dithiocarbamates
have diversified applications in the field of rubber chemistry
as vulcanization accelerator and antioxidants [12]. These have
gained acceptance as fungicides, insecticides and rodent repel-
lents [13–15]. The present study deals with synthesis, character-
2. Experimental
2.1. Materials and methods
All the reagents used were of AR grade. IR and far IR
spectra were recorded on Perkin-Elmer spectrum 2000 FT-IR
spectrometer. Electronic spectra were recorded on Beckman
DU-64 UV–vis spectrophotometer. Conductance measurements
were carried out on Elico conductivity Bridge Model CM-102,
India. 1H and 13C NMR were recorded on Bruker spectro-
spin advance 300 spectrometer and BAS-CV 50 W voltam-
metric analyser was used for recording the voltammograms of
complexes.
2.2. Preparation of dithiocarbamates
The dithiocarbamates were prepared by the method described
by Gilman and Blatt [16] with some modifications.
2.2.1. Preparation of KL1 and KL2
0.4 mol of corresponding amine was dissolved in the 14 ml
methanol and chilled to this a chilled solution of 2.24 g
(0.04 mol) potassium hydroxide in aqueous methanol was mixed
with constant stirring. The mixed solution was treated with an
∗
Corresponding author. Tel.: +91 11 27666616.
E-mail addresses: navneet92@rediffmail.com (N. Manav),
ajaykmishra1@yahoo.com (A.K. Mishra),
narenderkumar kaushik@yahoo.co.in (N.K. Kaushik).
1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2005.09.023

N. Manav et al. / Spectrochimica Acta Part A 65 (2006) 32–35
33
Table 2
ice-cold solution of 2.5 mL (0.04 mol) carbon disulphide (den-
Electronic spectra of dithiocarbamate complexes of Pt(IV)
sity 1.266) in 4 mL methanol keeping the temperature of the
reaction mixture below 10 ◦C. During the process, desired white
crystallineprecipitatesseparated. Itwasfilteredandwashedwith
ice-cold aqueous methanol and recrystallized from hot water.
λmax (nm)
log (ε)
[Pt(L1)2Cl2]
289
325
350
4.32
4.08
4.06
2.2.2. Preparation of NaL3 and NaL4
[Pt(L2)2Cl2]
[Pt(L3)2Cl2]
[Pt(L4)2Cl2]
304
350
4.10
3.79
A three necked flask was cooled in a freezing mixture of com-
mon salt and ice. First of all 2 g (0.05 mol) of sodium hydroxide
dissolved in minimum quantity of distilled water was added
followed by the addition of 3 mL (0.05 mL) of pure carbon
disulphide (density 1.2) through the separating funnel and to the
stirred mixture (0.05 mol) of distilled corresponding amine was
added. The mixture was stirred mechanically for two hours keep-
ing temperature below 5 ◦C when a yellowish-white crystalline
product separated out which was filtered, washed with small por-
tion of ether and finally recrystallized from acetone–petroleum
ether and dried under vacuum over CaCl2 at room temperature.
299
343
4.27
4.05
300
325
355
415
4.16
3.72
3.56
2.25
and 295 nm (log ε = 3.304) appear. Two absorption bands are
observed for ligand L2 at 270 nm (log ε = 3.134) and 300 nm
(log ε = 3.279). Ligand L3 absorbs at 272 nm (log ε = 3.027)
and 295 nm (log ε = 3.184). Ligand L4 absorbs at 273 nm
(log ε = 2.989) and 299 nm (log ε = 3.162). On complexation
these bands are shifted. All the complexes are found to be
diamagnetic. So the Pt(IV) complexes must be octahedral. Pt
(IV) is d6 system and four bands are expected corresponding
2.3. Preparation of complexes
2.3.1. Preparation of dithiocarbamate complexes
[Pt(L)2Cl2] where L = L1, L2, L3 and L4
The corresponding ligand L [where L = L1 (0.101 g,
0.50 mmol), L2 (0.104 g, 0.50 mmol), L3 (0.106 g, 0.50 mmol),
L4 (0.113 g, 0.50 mmol)] in distilled water was added to aque-
ous solution of K2PtCl6 (0.104 g, 0.25 m mol). The solution was
stirred and heated for two hours. The colour of the solution
changed to darkyellow (mustard)and yellowish orangecoloured
complex separated. It was centrifuged and washed with distilled
water several times.
3
3
1
1
to 1A1g → T1g, 1A1g → T2g, 1A1g → T1g and 1A1g → T2g
transitions [16]. Strong charge transfer transitions may inter-
fere and prevent the observation of all the expected bands
[17–21]. Strong bands ∼350 nm is assignable to a combina-
tion of metal ligand charge transfer (M → LCT) and d–d band.
The very intense band ∼420 is assignable to combination of
sulphur → metal charge transfer (L␲ → MCT) and d–d bands.
Electronic spectra of the complexes are depicted in Table 2.
3. Results and discussion
3.2. Infrared spectra
Elemental analysis (Table 1) reveals that complexes are of
good purity. All the complexes are soluble in DMSO and insol-
uble in most of the organic solvents. The molar conductance
values of the isolated complexes measured in d6-DMSO are
found to be less than 15 ꢀ−1 cm2 mol−1 suggesting their non-
electrolytic nature.
Three regions in IR spectra of dithiocarbamate complexes
are of particular importance. The stretching frequency region
1440–1550 cm−1 can be assigned to polar C—N partial double
---
---
bond of S2C—NR2 as reported by Chatt et al. [22].
The ν(C--- stretching frequency has been used to distinguish
S)
—
between the monodentate and bidentate behaviour of the
dithiocarbamate group. As reported by Bonati and Ugo [23] and
others [24], in case of monodentate dithiocarbamate ligand a
doublet arises around 1000 cm−1 separated by ≥20 cm−1 which
is due to non-equivalence of two C S stretching vibrations. On
the other hand in caser of bidentate dithiocarbamate a strong
singlet is observed in ∼1000 cm−1 region, which is indicative of
3.1. Electronic spectra
The electronic spectra of dithiocarbamates show high inten-
sity absorption due to chromophore NCS2. Two bands are
*
*
expected because of ␲ → ␲ and n → ␲ transitions. In UV
spectra of ligand L1 two bands at 273 nm (log ε = 3.268)
Table 1
Elemental analysis of dithiocarbamate complexes
Complexes
Found (calculated) (%)
C
H
N
S
Cl
Metal
[Pt(L1)2Cl2]
[Pt(L2)2Cl2]
[Pt(L3)2Cl2]
[Pt(L4)2Cl2]
20.35 (20.30)
28.13 (27.86)
28.19 (28.28)
32.94 (32.19)
2.65 (2.71)
1.78 (1.99)
4.78 (4.71)
4.68 (4.76)
4.98 (4.73)
4.23 (4.64)
4.32 (4.12)
4.49 (4.17)
21.80 (21.66)
21.95 (21.27)
18.50 (18.85)
19.73 (19.08)
12.70 (12.01)
11.43 (11.77)
11.32 (10.46)
10.94 (10.58)
33.80 (33.16)
33.14 (32.50)
30.13 (28.86)
29.90 (29.21)

34
N. Manav et al. / Spectrochimica Acta Part A 65 (2006) 32–35
Table 3
3.4. Cyclicvoltametric studies
IR frequencies (cm−1) of dithiocarbamates and their Pt(IV) complex (in KBr
pallets)
Over the last 20 years and so, electrochemical and chemical
studies of the redox properties of dithiocarbamate compounds
have demonstrated the ability of this ligand to stabilize a wide
range of oxidation states. In the case of platinum, well char-
acterized Pt(R2dtc)2 and [Pt(R2dtc)3]+ compounds exist and
conventional reductive elimination and oxidative addition reac-
tion occur [27,28]. Voltametric oxidation of Pt(R2dtc)2 is less
well characterized, although a small yield of [Pt(R2dtc)3]+ has
been observed in bulk electrolysis experiments [29], but no evi-
dence for any Pt(III) intermediates was reported in these studies.
Cyclic voltammetric reduction of all the Platinum complexes
gave irreversible peak for overall two electron process. Electron
transfer is assumed to be two electron only because Pt(III) if
formed is highly unstable oxidation state and is not detectable
with in the instrumental time limit. The next electron is then
quickly accepted by it to give Pt(II):
ν(C
ν(C
ν(M
ν(M
Cl)
N)
S)
S)
KL1
1462
1494
1463
1500
1464
1508
1465
1500
991, 1019
1004
990, 1015
1000
991, 1027
1009
987, 1013
1002
−
−
[Pt(L1)2Cl2]
KL2
390
−
293
−
[Pt(L2)2Cl2]
NaL3
390
−
293
−
[Pt(L3)2Cl2]
NaL4
385
−
294
−
[Pt(L4)2Cl2]
387
301
symmetrically, bound dithiocarbamate moiety. In present series
of dithiocarbamate complexes we observed only one strong band
around 1000 cm−1, which indicates that all the dithiocarbamate
ligands are bidentate and symmetrically bonded.
Far IR spectra contain the M–S stretching frequencies [25]
in the region 390–320 cm−1. The band at ∼280 is assigned to
ν(Pt Cl) vibrations. The important IR and far IR bands of dithio-
carbamate complexes are depicted in Table 3.
[Pt(L2)Cl2] + 2e− → [PtL2] + 2Cl−
The electron transfer is irreversible since no peak corresponding
to oxidation was observed on reversing the scan direction.
In some complexes, two irreversible reduction peaks (83.8
and 1037.8 mV) are arising which may be due to the reduc-
tion of the second geometrical isomer formed in solution only
(cis–trans isomerisation) during the CV measurements. This is
not due to two couples Pt(IV)/Pt(III) and Pt(III)/Pt(II) again
because Pt(III) is too short lived to be sensed by the electrode.
3.3. NMR spectra
3.3.1. 1H NMR spectra
1H NMR spectra of ligands and complexes were recorded in
d6-DMSO taking TMS as internal standards.
L1: δ (ppm) 4.26 (t, 4H, CH2 N), 3.46 (t, 4H, CH2 O);
[Pt(L1)2Cl2]: δ (ppm) 3.35–3.93 (m, 16H, CH2).
L2: δ (ppm) 6.6–7.2 (m, 5H, C6H5), 4.95 (s, br, 1H, NH);
[Pt(L2)2Cl2]: δ (ppm) 6.5–7.13 (m, 10H, C6H5), 5.03 (s, br,
2H, NH).
3.5. Antibacterial activity
Some of the samples were tested against Zymomonas mobilis,
Bacillus subtilis, Klebseilla aeroginosa, Escherichia coli and
Pseudomonasaeruginosa. Thedithiocarbamatecomplexeswere
less active against these bacteria strains. The antibacterial activ-
ity of the complexes is presented in Table 4.
L3: δ (ppm) 2.06 (s, 3H, CH3), 1.1–1.9 (m, 11H,
cyclohexyl); [Pt(L3)2Cl2]: δ (ppm) 2.10 (s, 6H, CH3),
1.2–1.97 (m, 22H, cyclohexyl).
L4: δ (ppm) 2.5 (q, 2H, CH2), 2.1 (t, 3H, CH3), 1.1–1.9 (m,
11H, cyclohexyl); [Pt(L4)2Cl2]: δ (ppm) 2.54 (q, 4H, CH2),
2.08 (t, 6H, CH3), 1.18–1.83 (m, 22H, cyclohexyl).
As reported by Tsipis and Manoussakis [26], in case of metal
dithiocarbamate complexes, sharp 1H NMR spectra without
being split indicate the non-coexistance of mono and bidentate
dithiocarbamate ligands.
3.6. In Vitro antitumour activity
In vitro activity against human colour adenocarcinoma
cell line, was cultured in RPMI 1640 medium supplemented
with 10% fetal calf serum (FCS), 100 ␮g/mL streptomycin.
A 100 ␮g/mL penicillin and 50 ␮g/mL gentamycine. For the
assay, 10,000 cells were plated per well of a 96 well tissue cul-
ture plate and allowed to adhere overnight at 37 ◦C in a 5%
CO2 incubator. Next day, the medium was changed to RPMI
1640 containing 5% FCS. The compound to be tested was dis-
solved in DMSO and subsequent serial dilutions were made in
3.3.2. 13C NMR
13C NMR of the compounds was recorded in d6-DMSO
10–20 ppm upfield shifts are observed for all the complexes for
NCS2 carbon in comparison to free ligands. This further sup-
−
ports the coordination via CS2
.
Table 4
Antibacterial activity of the complexes
Complex
Zymomonas mobilis
Bacillus subtilis
Klebseilla aeroginosa
Escherichia coli
Pseudomonas aeruginosa
[Pt(L1)2Cl2]
[Pt(L3)2Cl2]
[Pt(L4)2Cl2]
+
++
−
−
−
−
−
−
+
+
+
+
++
−
++

N. Manav et al. / Spectrochimica Acta Part A 65 (2006) 32–35
35
RPMI 1640 medium. The cells were treated with various con-
centrations of the compounds (10 ␮M–10 pM) and allowed to
incubate at 37 ◦C in a CO2 incubator. A second dose of the
compound was added to the cells after 24 h and thereafter the
cells were incubated for a further 24 h. Appropriate controls for
assessing cytotoxicity due to DMSO were included in the assay.
Cytotoxicity was assessed using MTT (3-[4,5-dimethylthiazol-
2-yl]-2,5-diphenyltetrazolium bromide) [30].
One complex was tested for the antitumour activity. The com-
plex was tested on primary adenocarcinoma (colour). Appro-
priate controls for DMSO (solvent) were included in the final
values.
[7] K. Inoue, T. Mukaiyama, I. Mitsui, M. Ogawa, Cancer Chemopther.
Pharmacol. 15 (1985) 208.
[8] R.F. Borch, J.C. Katz, P.H. Lieder, M.E. Pleasants, Proc. Natl. Acad.
Sci. U.S.A. 77 (1980) 5441.
[9] G.R. Gale, L.M. Atkins Jr., E.M. Walker, Ann. Clin. Lab. Sci. 12 (1982)
345.
[10] D.L. Bodenner, P.C. Dedon, P.C. Keng, J.C. Katz, R.F. Borch, Cancer
Res. 46 (1986) 2751.
[11] L. Pendyalia, Y. Kidani, R. Perez, J. Wilkes, R.J. Bernacki, P. Creaven,
J. Cancer Lett. 97 (1985) 177.
[12] G.D. Thorn, R.A. Ludwig, The Dithiocarbamates and Related Com-
pounds, Elsevier Publishing Company, New York, 1962.
[13] H.G. Guy, J. Econ. Entomol. 29 (1936) 467.
[14] R.D. McMullen, Nature 184 (1959) 1338.
[15] A.E. Dimond, J.W. Heuberger, J.G. Horsfall, Phytopathology 33 (1943)
1095.
4. Conclusion
[16] H. Gilman, A.H. Blatt, Organic Synthesis, vol. 1, John Wiley, New York,
1958, p. 448.
The dithiocarbamate complexes were found less active
againstZ. mobilis, B. subtilis, K. aeroginosa, E. coliandP. aerug-
inosa bacteria strains. In in vitro study, the complex showed
good activity at 100 and 10 nM solutions but proliferation started
in complexes on further dilution. It was further tested for and
showed no adverse effect on the various organs like liver, kid-
neys, brain and bladder of rabbits.
[17] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, New York,
1984.
[18] J. Selbin, T.R. Ortolazo, F. Smith, J. Inorg. Chem.
1315.
2 (1962)
[19] D.X. West, C.S. Carlson, A.E. Liberta, J.N. Albert, C.R. Daniel, Trans.
Met. Chem. 15 (1990) 341.
[20] D.X. West, M.S. Lockwood, A. Liberta, X. Chen, R.D. Willet, Trans.
Met. Chem. 18 (1993) 221.
[21] (a) D. Kovala-Demertzi, A. Michaelides, A. Aubry, Inorg. Chim. Acta
194 (1992) 189;
References
(b) D. Kovala-Demertzi, A. Domopoulou, D. Nicholls, A. Michaelides,
A. Aubry, J. Coord. Chem. 30 (1993) 265.
[1] V. Alverdi, L. Giovagnini, C. Marzano, R. Seraglia, F. Beltio, S. Sitran,
R. Graziani, D. Fregona, J. Inorg. Biochem. 98 (2004) 1117.
[2] N.J. Farrell, in: B.R. James, R. Ugo (Eds.), Catalysis by Metal Com-
plexes, vol. 11, Kluwer Academic Publishers, Dordrecht, The Nether-
lands, 1989, p. 46.
[3] N. Manav, A.K. Mishra, N.K. Kaushik, Spectrochim. Acta 60A (2004)
3087.
[4] Y.E. Kwon, K.J. Whang, Y.J. Park, K.H. Kim, Bioorg. Med. Chem. 11
(2003) 1669.
[5] C. Marzano, A. Trevisan, L. Giovagnini, D. Fregona, Toxicol. Vitro 16
(2002) 413.
[6] D.D. Von Hoff, R. Schilsky, C.M. Reichert, R.L. Reddick, M.
Rozencweig, R.C. Young, F.M. Muggia, Cancer Treat. Rep. 63 (1979)
1527.
[22] J. Chatt, L.A. Duncanson, L.M. Venazi, Suomen Kem. 29 (1956) 75;
J. Chatt, L.A. Duncanson, L.M. Venazi, Nature 177 (1956) 1042.
[23] F. Bonati, R. Ugo, J. Org. Met. Chem. 10 (1967) 57.
[24] B.F.G. Johnson, K.H. Al-Obalidi, J.A. Mecleverty, J. Am. Chem. Soc.
19 (1969) 668.
[25] B.B. Kaul, K.B. Pandeya, J. Inorg. Nucl. Chem. 40 (1978) 171.
[26] C.A. Tsipis, G.E. Manoussakis, Inorg. Chim. Acta 18 (1976) 35.
[27] J. Willemse, J.A. Cras, J.J. Steggerda, C.P. Keijzers, Struct. Bond. 28
(1976) 83.
[28] J. Willemse, J.A. Cras, Recl. Trav. Chim. Pays-Bas 91 (1972)
1309.
[29] J.G.M. Van der Linden, A.H. Dix, Inorg. Chim. Acta 35 (1979) 65.
[30] N.K. Singh, A. Srivastava, Transit. Met. Chem. 25 (2000) 133.