Synthesis, characterization and anticancer studies of ...

European Journal of Medicinal Chemistry 46 (2011) 4071e4077

Contents lists available at ScienceDirect

European Journal of Medicinal Chemistry journal homepage: http://www.elsevier.com/locate/ejmech

Original article

Synthesis, characterization and anticancer studies of mixed ligand dithiocarbamate palladium(II) complexes Hizbullah Khan a, b, c, Amin Badshah b, *, Ghulam Murtaz b, Muhammad Said b, Zia-ur- Rehman b, Christine Neuhausen d, Margarita Todorova e, Bertrand J. Jean-Claude e, Ian S. Butler a a

Department of Chemistry, McGill University, Montreal, QC, Canada H3A 2K6 Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan Department of Chemistry, Malakand University, Lower Dir, KPK, Pakistan d Laboratoire de Cristallographie, Ecole Polytechnique Fédérale de Lausanne, Switzerland e Royal Victoria Hospital, Department of Medicine, Montreal, QC, Canada H3A 1A1 b c

a r t i c l e i n f o

a b s t r a c t

Article history: Received 9 March 2011 Received in revised form 22 May 2011 Accepted 6 June 2011 Available online 14 June 2011

Six mixed ligand dithiocarbamate Pd(II) complexes (1e6) of general formula [(DT)Pd(PR3)Cl], where DT ¼ dimethyldithiocarbamate (1, 5), diethyldithiocarbamate (2, 3), dicyclohexyldithiocarbamate (4), bis(2-methoxyethyl)dithiocarbamate (6); PR3 ¼ benzyldiphenylphosphine (1), diphenyl-2-methoxyphenylphosphine (2), diphenyl-p-tolylphosphine (3), diphenyl-m-tolylphosphine (4), tricyclohexylphosphine (5), diphenyl-2-pyridylphosphine (6) have been synthesized and characterised using Elemental analysis, FT-IR, Raman and multinuclear magnetic resonance (NMR) spectroscopy. Compounds 1 and 2 were also characterized by single crystal X-ray diffraction technique (XRD). The XRD study reveals that the Pd(II) moiety has a pseudo square-planar geometry, in which two positions are occupied by the dithiocarbamate ligand in a bidentate fashion, while at the remaining two positions organophosphine and chloride are present. The anticancer activity of the synthesized metallodrugs was checked against DU145 human prostate carcinoma (HTB-81) cells, the IC50 values indicate that the compounds are highly active against these cells. These Pd(II) complexes also show moderate antibacterial activity against gram positive and gram negative bacteria. Ó 2011 Elsevier Masson SAS. All rights reserved.

Keywords: Palladium(II) Dithiocarbamate DU145 Crystal structure Mixed ligand

1. Introduction Cancer is a biggest health hazard for the humanity [1]. Despite the dramatic development of antitumour drugs, the cancer death rate is remain constant (ca. 200 deaths for every 100,000 people) over the last 30 years. In USA cancer surpassed heart disease in 2005; still every fifth death is caused by cancer [2,3]. Cisplatin, carboplatin, oxalylplatin, nedaplatin and lobaplatin (Fig. 1), are the important currently used platinum based anticancer drugs [4,5]. Cisplatin cis-diaminedichloroplatinum(II) was rediscovered by Barnett Rosenberg in 1965 during his study of mitotic cell division in Escherichia coli bacteria [6,7]. Rosenberg observed the power of inhibition of cell division, of cisplatin and then become interested in its use as an anticancer drug. In 1978 FDA approved cisplatin as an anticancer drug for testicular and ovarian malignancies [8,9]. Cisplatin is well established metal based antitumour agent,

* Corresponding author. Tel.: þ92 51 90642131; fax: þ92 51 90642241. E-mail address: [email protected] (A. Badshah). 0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ejmech.2011.06.007

however, its use is restricted due to acquired cell resistance after continuous treatment and lethal side effects such as nausea and liver and kidney failure, typical of heavy metal toxicity [10e15]. Platinum based drugs are believed to induce apoptosis (programmed cell death) in targeted organism by distorting its DNA and by triggering cellular processes [16,14]. Platinum based drugs have high affinity for sulphur atom and thus interact with sulphur containing biomolecules like amino acids (cysteines and methionines), peptides (glutathione), proteins (metallothionein) and many others. The interaction with sulphur moiety causes inactivation of Pt(II) compounds, cellular resistance to platinum and toxic side effects such as nephrotoxicity [17]. On the basis of structure and thermodynamic resemblance between palladium(II) and platinum(II) complexes [18e21], there is also much interest in the synthesis and designing of palladium drugs that can have maximum pharmacological action. In this investigation, some mixed ligand palladium(II) complexes have shown very promising results [22e24]. Palladium(II) metallodrugs are good models to study their interaction with biological molecules in vivo because of their more labile nature than platinum(II)

4072

H. Khan et al. / European Journal of Medicinal Chemistry 46 (2011) 4071e4077

Fig. 1. Currently used platinum based anticancer drugs.

compounds (on average 103 times faster than platinum) and in vitro easy of hydration [25]. It is suggested that palladium complexes are more useful in the treatment of cisplatin resistive gastrointestinal tumours [26]. Mixed ligand dithiocarbamateeamine complexes of palladium(II) have antitumour activity comparable to the cisplatin and circumvented the cross resistance to cisplatin. Sulphur containing ligands are currently under trials as chemoprotectants in platinum based chemotherapy, in particular thiocarbonyl, thiol and dithiocarbamate ligands have the ability to modulate the nephrotoxicity of the cisplatin [27]. Dithiocarbamates have the ability to stabilize transition metals in a variety of oxidation states [28]. Dithiocarbamates reduce the cytotoxicity of platinum based drugs by selective removal of platinum from enzymeethiol complex by nucleophilic attack of sulphur atoms on platinum moiety. In addition to this, they have the potency to protect the normal tissues without undermining the cytostatic activity of parent drugs [29]. Keeping in mind all these points, we aimed to synthesize and characterize six new mixed ligand palladium(II) complexes of the typical formula [(DT)Pd(II)(PR3)Cl] DT ¼ dimethyldithiocarbamate, diethyldithiocarbamate, dicyclohexyldithiocarbamate or bis(2methoxyethyldithiocarbamate; PR3 ¼ benzyldiphenylphosphine, diphenyl-2-methoxyphenyl-phosphine, diphenyl-p-tolylphosphine, diphenyl-m-tolylphosphine, tricyclohexylphosphine or diphenyl-2-pyridylphosphine). The antitumour activity of the palladium(II) complexes was determined against human prostate cancer cells and the antibacterial activity were evaluated using gram positive and gram negative bacteria.

2. Results and discussion 2.1. Synthesis of the dithiocarbamate and organophosphine palladium(II) complexes and their characterization The complexes 1e6 were synthesised by reacting the dithiocarbamate ligands and (PR3)2PdCl2 in dichloromethane (Scheme 1). These complexes are soluble in common organic solvents and stable under normal conditions of temperature and pressure. The FT-IR and Raman spectra of the Pd(II) complexes 1e6 display stretching frequencies at 1473e1434 (CN), 1100e1055 (SCSasym), 754e692 (SCSsym) and 412e378 cm1 (PdeS), that signify the coordination of the dithiocarbamate ligand. The diagnostic peak in the range of (1473e1434 cm1) is assignable to the CeN stretching frequency, typical of dithiocarbamate complexes [29]. These values lie between the range reported for CeN single bond (1250e1360 cm1) and C]N double bond (1640e1690 cm1), and is an indication of partial double bond character in CeN bond [30,31]. This fact was further supported by X-ray crystallographic analysis of complexes 1 and 2. The disappearance of an SeH peak in the range of 2550e2700 cm1 in all complexes suggests the detachment of hydrogen atom and coordination of ligand with palladium(II) centre. The emergence of a single peak for the SCS moiety in the range of 1100e1055 cm1 (SCSasym) and a single vibration in the region 754e692 cm1 (SCSsym) show the bidentate coordination of dithiocarbamate ligand [32]. The 1H NMR spectra of the Pd(II) complexes make obvious the disappearance of the SH peak, that further support the coordination

Scheme 1. Synthesis of mixed ligand palladium(II) complexes, 1e6.


of the dithiocarbamate ligand with metal centre. The other proton frequencies in the ligand and metal complexes don’t show any appreciable change. The bond formation between the dithiocarbamate ligand and the palladium(II) centre can be assessed by the slight upfield shift of SCS carbon atom in contrast to the free ligand. The slight displacement in the upfield may be due to the accumulation of high electron density on SCS carbon upon coordination of the two sulphur atoms with the metal centre. The 13C chemical shift of SCS carbon atom in the mixed ligand Pd(II) complexes appears in the range of 210.1e206.1 ppm. The 31P chemical shift, in the synthesised complexes, was observed in the range of 51.7e20.3. The downfield shift of 31P value in Pd(II) complexes than the free organophosphines confirms the coordination of phosphorus atom to the metal moiety. 2.2. Structural study of complexes 1 and 2 The ORTEP representations of compounds 1 and 2 with selected bond distances and angles are shown in Figs. 2 and 3 respectively. Complex 1 crystallizes in a monoclinic crystal system P2(1)/c whereas 2 crystallize in a (P-1) triclinic system. Both complexes exhibit similar pseudo square-planar geometry with the dithiocarbamate ligand occupy two adjacent coordination sites while the chloride and the phosphine inhabit the two remaining sites. The largest distortion from the normal geometry comes from the bidentate ligand (S(1)ePd(1)eS(2) of 75.29(3) and S(1)ePd(1)eS(2) 75.11(5) for 1 and 2, respectively) which causes the trans S(2)ePd(1)eCl(1) and P(1)ePd(1)eS(1) angles to be between 171.72(3) and 172.19(2) , smaller than the expected value of 180 . The asymmetry observed in the PdeS distances is typical for square planar systems and is reflecting the trans effect of the ligands in play. In both complexes, the PdeS bond lengths trans to the phosphine ligand are longer ([2.3592(8) and 2.3643(14) Å] for 1 and 2, respectively than the PdeS bond lengths trans to the chloride ([2.2751(8) and 2.2694(13) Å] for 1 and 2, respectively). The largest discrepancy in the PdeS bond lengths for complex 2 (DPd-S of 0.0949 Å for 2 and 0.0841 Å for 1)

4073

reflects the better donating capability of the PPh2(Ph-2eOCH3) than the benzyldiphenylphosphine. The both SeC distances in 1 and 2 (1.693(3) and 1.728(3) Å) are intermediate between single bond, CeS (1.82 Å) and double bond C]S (1.60 Å) distances. Similarly, the C(20)eN(1) bond lengths of 1.311(3) Å for 1 and 1.315(6) Å for 2 are significantly shorter than a normal CeN bond distance (1.47 Å) and longer than a C]N bond length (1.28 Å) [33]. These bond values clearly demonstrate the resonance phenomenon in N-SCS moiety. 2.3. Biological activity 2.3.1. Antitumour activity The synthesized compounds were tested for their antitumour activity against DU145 human prostate carcinoma (HTB-81) cells (Fig. 4). The IC50 values reveal that all the five tested complexes are significantly active against the cisplatin resistant [34], DU145 carcinoma cells. The 50% inhibitory concentrations (IC50) of the compounds are listed in Table 1, which are lying in the low micromolar concentrations range. The complex 5 is the most active with IC50 of 1.33 mM while the compound 1 has the highest IC50 value. Both complexes 1 and 5 have similar dithiocarbamate ligand but they have different organophosphine moiety. The higher cytotoxicity of complex 5 may be accredited to the electron donating tricyclohexyl group in organophosphine ligand. The PdeP bond will be stronger owing to the electron donating ability of tricyclohexylphosphine and the complex will remain integrated, having more chance to reach the target DNA. The compound 1 has electron-withdrawing phenyl groups in organophosphine moiety. The PdeP bond may be weaker and the complex may have higher tendency to dissociate. The movement of this dissociated complex towards DNA may be interrupted by other groups in the cell, like glutathione, cysteines and methionines [5]. The second highest activity of complex 6 is presumably due to the presence of 2-pyridyl that have the potency to form hydrogen bond with DNA bases. The lowest activity of 4 and 3 can be ascribed to there minimum lipophilic character.

Fig. 2. ORTEP diagram (50% probability) of (1). Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Pd(1)-P(1) 2.2649(8); Pd(1)-Cl(1) 2.3106(9); Pd(1)eS(1) 2.3592(8); Pd(1)eS(2) 2.2751(9); S(1)eC(20) 1.693(3); S(2)eC(20) 1.728(3); C(20)eN(1) 1.311(3); P(1)ePd(1)eCl(1) 88.59(3); P(1)ePd(1)eS(2) 99.06(3); S(2)ePd(1)eS(1) 75.29(3); Cl(1)ePd(1)eS(1) 96.79(4); S(2)ePd(1)eCl(1) 171.72(3); P(1)ePd(1)eS(1) 172.19(2); C(21)eN(1)eC(22) 116.9(3); C(20)eN(1)eC(22) 121.4(3); C(20)e N(1)eC(21) 121.6(3); S(1)eC(20)eS(2) 111.7(14).

4074


Fig. 3. ORTEP diagram (50% probability) of (2). Hydrogen atoms have been omitted for clarity. Selected bond lengths (Ǻ) and angles (deg): Pd(1)eP(1) 2.303(13); Pd(1)eCl(1) 2.3334(13); Pd(1)eS(1) 2.2694(13); Pd(1)eS(2) 2.3643(14); S(1)eC(20) 1.728(5); S(2)eC(20) 1.705(5); C(20)eN(1) 1.315(6); P(1)ePd(1)eCl(1) 96.66(5); P(1)ePd(1)eS(2) 169.12(4); S(2)ePd(1)eS(1) 75.11(5); Cl(1)ePd(1)eS(1) 169.17(5); S(2)ePd(1)eCl(1) 94.08(5); P(1)ePd(1)eS(1) 94.16(5); C(20)eS(1)ePd(1). 88.18(16); S(2)eC(20)eS(1) 110.8(3).

2.3.2. Antibacterial assay The mixed ligand dithiocarbamate Pd(II) complexes have been screened for their antibacterial activity against 2 g negative (E coli, Klebsiella pneumonia) and 3 g positive bacterial strains (Staphylococcus epidermidis, Staphylococcus aureus, Bacillus subtilis). The antibacterial activities of the synthesized metallodrugs are listed in Table 2 and shown in Fig. 5. The activity of the complexes 1e6 is fairly good but less than the standard drug used. In general, the activity of the compounds varies in the sequence 4 ˃ 2 ˃ 3 ˃ 6 ˃ 1 ˃ 5. This implies that the length and nature of the alkyl group on the NCS2 moiety has a seminal role in the antibacterial action. This situation can be understood in term of chelation theory, which states that the polarity of the metal ion is reduced upon complexation, which results in an increase in the lipophilicity of the metal complexes and make them easy to permeate through the cell membrane of the bacterium. The high activity of 4 can be attributed to the bulky cyclohexyl substituent that is a good electron donating group among all and thus increases the lipophilic character of the complex by strengthening metal ligand bond. The comparable activity of the 2 and 3 is due to the presence of ethyl substituent in both. The lower activity of 6 than both 2 and 3 may be due to the presence of electron-withdrawing methoxy group that reduces the electron density on NCS2 moiety and thus reduces its ability to coordinate with metal centre or in other word decreases the lipophilicity of the complex. However, the high activity of 6 than 1 and 5 can be explained on the basis of 2-pyridyl that can make interaction with cell constituents of the bacterium cell via hydrogen bonding.

4. Experimental section All the experiments were performed at room temperature and pressure. Dimethylamine, benzyldiphenylphosphine, diethylamine, diphenyl-2-methoxyphenylphosphine, diphenyl-p-tolylphosphine, dicyclohexylamine, diphenyl-m-tolylphosphine, bis(2-methoxyethyl)amine, dicyclohexylamine, diphenyl-2-pyridylphosphine hydrochloric acid, carbon disulfide and palladium(II) chloride were purchased from Aldrich and were used without further purification. The solvents used were dried and purified by the standard methods. NMR spectra were recorded on Mercury 200 MHz, Mercury 300 MHz, Bruker 300 MHz and VNMRS500 spectrometers. 1H NMR (300.13 MHz and 499.89 MHz): CDCl3 (7.26 ppm from SiMe4) and DMSO-d6 (2.49 ppm from SiMe4), internal standard SiMe4. 13C NMR (75.46 MHz and 125.69 MHz): internal standard TMS; 31P NMR (121.49 MHz, CDCl3). The splitting of proton resonances in the 1H NMR spectra are shown as, s ¼ singlet, d ¼ doublet, t ¼ triplet and m ¼ multiplet (showing a complex pattern). IR spectra were recorded on a NICOLET 6700 FT-IR instrument in the range of 4000-400 cm1 and Raman spectra (1 cm1) were measured with an InVia Renishaw spectrometer, using argon-ion (514.5 nm) and near-infrared diode (785 nm) lasers. WiRE 2.0 software was used for the data acquisition and spectra manipulations. The elemental analyses were conducted on a LECO-183 CHNS analyzer. Melting points were measured on Stuart SMP10 apparatus and are uncorrected. 4.1. Synthesis of complexes 1e6

3. Conclusions Six new mixed ligands palladium(II) complexes have been synthesised and charaterized. The spectroscopic data and X-ray single crystal analyses reveal that all the compounds have pseudo square-planar geometry. The antitumour screening of these compounds proved them to be highly active against cisplatin resistant DU145 human prostate cancer cells and need further investigations to be market as a new anticancer drug. They are also active against the different gram positive and gram negative pathogens.

To the methanolic solution of palladium(II) chloride few drops of concentrated HCl was added and the resulting solution was refluxed for 30 min. The organophosphine dissolve in dry acetone was then added to the palladium(II) chloride solution in 2:1 molar ratio, and this solution was refluxed for 3 h with constant stirring. The solid product was filtered and dried at room temperature. The organophosphinepalladium(II) chloride dissolve in dichloromethane was then reacted with the appropriate dithiocarbamate in 1:1 molar ratio under reflux for 24 h. The solution thus obtained, was filtered and then was rotary evaporated to get golden yellow


4075

Fig. 4. The cell growth of DU145 human prostate carcinoma (HTB-81) cells at various concentrations of the Pd(II) complexes.

solid. The solid product was recrystallized form dichloromethane, n-hexane and diethyl ether (2:1:1) mixture. Only for compounds 1 and 2 the golden yellow needle shaped crystals were obtained. 4.1.1. [Pd(dimethyldithiocarbamate)(PPh2(benzyl)Cl)] (1) Quantities used were 0.07 g (0.58 mmol) of dimethyldithiocarbamate and 0.32 g (0.58 mmol) of Pd(PPh2(benzyl))2Cl2 in 30 mL of dichloromethane. Yield: 0.22 g (75%). M. p. 242e243 C. FT-IR (powder, cm1): 3054 n(CeH, aromatic), 2949 n(CeH, aliphatic), 1434 n(CeN), 1100 n(SCSasym), 692 n(SCSsym) Raman (powder, cm1): 378 n(PdeS), 299 n(PdeCl), 245, n(PdeP). 1H NMR (300 MHz, CDCl3) d-ppm: 7.45e7.18 (m, 15H, AreH), 4.01 (d, 2H, eCH2e, 2JH-P ¼ 11.7 Hz), 3.26 (s, 3H, eCH3), 3.13 (s, 3H, eCH3). 13C NMR (75.47 MHz, CDCl3) d-ppm: 207.6 (SCS) {ligand SCS ¼ 210.2 ppm}, 134.1, 133.0, 130.7, 129.0, 128.4, 126.7 (AreC), 38.1

Table 1 The 50% inhibitory concentration (IC50) of the mixed ligand Pd(II) compounds. Compound

1

3

4

5

6

IC50

6.94 mM

5.71 mM

3.10 mM

1.33 mM

1.55 mM

(-CH2-, 1JP-C ¼ 90 Hz), 33.0 (eCH3), 32.7 (CH3). 31P NMR (121.49 MHz, CDCl3) d-ppm: 51.7. Anal. Calc. for C22H23ClNPPdS2: C, 49.08; H, 4.31; N, 2.60; S, 11.91 Found: C, 49.12; H, 4.32; N, 2.62; S, 11.94. Table 2 Antibacterial activityaec (diameter of inhibition zone) of complexes 1e6 against five different bacterial pathogens. Compound Escherichia Klebsiella coli pneumonia

Staphylococcus Staphylococcus Bacillus epidermidis aureus subtilis

1 2 3 4 5 6 Reference drug

18 17 16 20 18 20 35

14 16 18 22 14 16 26

14 17 14 16 14 15 26

15 18 17 16 15 14 35

15 14 18 20 15 14 35

In vitro agar well-diffusion method, conc. 1 mgmL1 DMSO. Reference drug Streptomycin, 10 mg/disc. c Zone diameter (Activity): Below 9 mm (no activity), 9e12 mm (non significant), 13e15 mm (low activity), 16e18 mm (good activity), above 18 mm (significant activity). a

b

4076


Fig. 5. Diagrammatic representation of antibacterial activity of complexes 1e6.

4.1.2. [Pd(diethyldithiocarbamate)(PPh2(Ph-2eOCH3)Cl)] (2) Quantities used were 0.03 g (0.20 mmol) of diethyldithiocarbamic acid and 0.15 g (0.20 mmol of Pd(PPh2(Ph2eOCH3)2Cl2)) in 25 mL dichloromethane. Yield 0.08 g (70%). M. p. 180e181 C. FT-IR (powder, cm1): 3052 n(CeH, aromatic), 2925 n(CeH, aliphatic), 1450 n(CeN), 1080 n(SCSasym); 740 n(SCSsym), Raman (powder, cm1): 400 n(PdeS) 330 n(PdeCl) 220 n(PdeP). 1H NMR (300 MHz, CDCl3) d-ppm: 7.76e6.73 (m, 14H, AreH), 4.06 (q, 2H, eCH2Ne, 3JH-H ¼ 6.9 Hz), 3.77 (s, 3H, eOCH3), 3.17 (q, 2H, eCH2e, 3JH-H ¼ 7.5 Hz), 1.36 (t, 3H, eCH3, 3JH-H ¼ 7.5 Hz), 1.22 (t, 3H, -CH3, 3JH-H ¼ 7.2 Hz). 13C NMR (75.47 MHz, CDCl3) d-ppm: 206.1 (SCS) {ligand SCS ¼ 208.7 ppm}, 137.8, 136.5, 128.9, 128.6, 123.2, 121.2, 111.3 (ArC), 164.0 (ArCeOCH3), 55.7 (eOCH3), 47.8 (eCH2e), 40.5 (eCH2e), 12.4 (eCH3), 10.7 (eCH3). 31P NMR (121.49 MHz, CDCl3) d-ppm: 20.3. Anal. Calc. for C24H27ClNOPPdS2: C, 49.49; H, 4.67; N, 2.40; S, 11.01. Found: C, 49.55; H, 4.71; N, 2.36; S, 11.06. 4.1.3. [Pd(diethyldithiocarbamate)(PPh2-p-tolyl)Cl] (3) Quantities used were 0.03 g (0.20 mmol) of diethyldithiocarbamic acid and 0.15 g (0.20 mmol) of Pd(PPh2-p-tolyl)2Cl2 in 30 mL dichloromethane. Yield 0.09 g (80%). M. p. 185e186 C. FT-IR (powder, cm1): 2920 n(CeH, aliphatic), 1459 n(CeN), 1097 n(SCSasym); 719 n(SCSsym); Raman (powder, cm1): 385 n(PdeS), 330 n(PdeCl), 225 n(PdeP). 1H NMR (500 MHz, CDCl3) d-ppm: 7.12e7.22 (m, 14H, ArH), 3.70 (q, 2H, eCH2e, 3JH-H ¼ 7.5 Hz), 3.55 (q, 2H, eCH2e, 3JH-H ¼ 7.0 Hz), 2.38 (s, 3H, AreCH3), 1.17 (t, 3H, eCH3, 3JH-H ¼ 7.0 Hz), 0.92 (t, 3H, eCH3, 3JH-H ¼ 7.5 Hz). 13C NMR (75.45 MHz, CDCl3) d-ppm: 207.1 (SCS) {ligand SCS ¼ 208.7 ppm}, 141.3, 134.9, 134.4, 132.3, 131.9, 130.6, 129.5, 128.3 (ArC), 43.7, 43.5 (-CH2-), 29.7 (AreCH3), 14.1, 14.0 (CH3e). 31P NMR (80.98 MHz, CDCl3) d-ppm: 27.0. Anal. Calc. for C24H27ClNPPdS2: C, 50.89; H, 4.80; N, 2.47; S, 11.32. Found: C, 50.83; H, 4.78; N, 2.47; S, 11.30. 4.1.4. [Pd(dicyclohexyldithiocarbamate)(PPh2-m-tolyl)Cl] (4) Quantities used were 0.03 g (0.12 mmol) of dicyclohexyldithiocarbamic acid and 0.09 g (0.12 mmol) of Pd(PPh2-m-tolyl)2Cl2 in 25 mL of dichloromethane. Yield 0.07 g (75%). M. p. 232e233 C. FT-IR (powder, cm1): 2924 n(CeH, aliphatic), 1435 n(CeN), 1071 n(SCSasym), 754 n(SCSsym), Raman (powder, cm1): 380 n(PdeS), 335 n(PdeCl), 233 n(PdeP). 1H NMR (300 MHz, CDCl3) d-ppm: 7.80e6.83 (m, 14H, ArH), 3.55 (s, 3H, AreOCH3), 2.16 (m, 2H, eNCHe), 0.90e2.20 (m, 22H, eC6H11). 13C NMR (75.45 MHz, CDCl3) d-ppm: 207.3 (SCS) {ligand SCS ¼ 209.6 ppm}, 164.3 (ArC), 138.3, 137.2, 136.4, 128.6, 128.8, 121.1, 111.3 (ArC), 57.2 (-OCH3), 64.3, 29.3, 25.4, 26.0,(eC6H11). 31P NMR (80.98 MHz, CDCl3) d-ppm: 28.6. Anal. Calc. for C32H39ClNOPPdS2: C, 55.65; H, 5.69; N, 2.03; S, 9.29. Found: C, 55.60; H, 5.67; N, 2.03; S, 9.27.

4.1.5. [Pd(dimethyldithiocarbamate)(P-(cyclohexyl)3)Cl] (5) Quantities used were 0.03 g (0.25 mmol) dimethyldithiocarbamate and 0.19 g (0.25 mmol) Pd(P-(cyclohexyl)3)2Cl2 in 30 mL of dichloromethane. Yield 0.10 g (73%). M. p. 198e199 C. FT-IR (powder, cm1): 2923 n(CeH, aliphatic), 1442 n(CeN), 1060 n(SCSasym), 747 n(SCSsym). Raman (powder, cm1) 379 n(PdeS), 337 n(PdeCl), 226 n(PdeP). 1H NMR (300 MHz, CDCl3) d: 3.12 (s, 3H, eCH3), 3.20 (s, 3H, CH3) 1.88e0.83 (m, 33H, eC6H11). 13C NMR (75.47 MHz, CDCl3) d 207.0 (SCS) {ligand SCS ¼ 210.2 ppm}, 68.1 (eCH3), 38.7e22.7 (eC6H11). 31P NMR (80.98 MHz, CDCl3) d 27.1. Anal. Calc. for C21H21ClNPPdS2: C, 48.10; H, 4.04; N, 2.67; S, 12.23. Found: C, 48.15; H, 4.02; N, 2.68; S, 12.26. 4.1.6. [Pd(bis(2-methoxyethyl)dithiocarbamate)(PPh2-2-pyridyl)Cl] (6) Quantities used were 0.14 g (0.57 mmol) bis(2-methoxyethyl) dithiocarbamate and 0.4 g (0.57 mmol) of Pd(PPh2-2-pyridyl)2Cl2 in 25 mL of dichloromethane. Yield 0.22 g (65%). M. p. 165e166 C. FTIR (powder, cm1): 3050 n(CeH, aromatic), 2933 n(CeH, aliphatic), 1473 n(CeN), 1055 n(SCSasym), 754 n(SCSsym). Raman (powder, cm1) 412 n(PdeS), 341 n(PdeCl), 213 n(PdeP). 1H NMR (300 MHz, CDCl3) d: 8.77e7.30 (m, 14H, ArH), 4.00 (t, 2H, eOCH2e, 3JH3 H ¼ 5.1 Hz), 3.87 (t, 2H, eOCH2e, JH-H ¼ 5.1 Hz), 3.64 (t, 2H, 3 eCH2Ne, JH-H ¼ 5.1 Hz), 3.52 (t, 2H, eCH2Ne, 3JH-H ¼ 5.1 Hz) 3.33 (s, 3H, CH3Oe) 3.30 (s, 3H, CH3Oe). 13C NMR (75.47 MHz, CDCl3) d 210.1 (SCS) {ligand SCS ¼ 212.8 ppm}, 157.3, 148, 134.5, 131.1, 128.6, 124.3 (ArC), 70.2 (eOCH2e), 58.8 (eCH2Ne), 53.7 (CH3O-). 31P NMR (80.98 MHz, CDCl3) d 27.5. Anal. Calc. for C24H28ClN2O2PPdS2: C, 46.99; H, 4.60; N, 4.57; S, 10.45 Found: C, 47.10; H, 4.64; N, 4.60; S, 10.49. 4.2. Structural studies of complexes 1 and 2 The block crystals were mounted on a glass fibre using epoxy glue. The measurements were made at 293 K on a STOE IPDS image plate detector diffractometer equipped with graphite monochromated Mo Ka radiation. The program used for retrieving cell parameters, data collection and data integration was STOE X-AREA [35]. The structures were solved and refined by using SHELXS-97 and SHELXL-97 (Sheldrick, 1997) and all non-H atoms were refined anisotropically, with the hydrogen atoms placed at idealized positions. 4.3. Anticancer activity DU145 human prostate carcinoma (HTB-81) cells were obtained from the American Type Culture Collection (ATCC catalogue


number). Cells were maintained in Roswell Park Memorial Institute (RPMI-1640) medium (Wisent Inc., St-Bruno, Canada) supplemented with 10% FBS, 10 mM HEPES, 2 mM L-gutamine and 100 g/ mL penicillin/streptomycin (GibcoBRL, Gaithersburg, MD). All assays cells were plated 24 h before drug treatment. 50 mmol stock concentrations of the compounds were prepared in DMSO. Nine serial dilutions of the compounds were used to treat the cells and the final concentration of DMSO on cells does not exceed 0.05%. In the growth inhibition assay, DU145 prostate cancer cells were plated at 5000 cells/well in 96-well flat-bottom microtiter plates (Costar, Corning, NY). After 24 h incubation, cells were exposed to different concentrations of each compound continuously for four days. The remaining live cells were fixed using 50 mL of cold trichloroacetic acid (50%) for 60 min at 4 C, washed with water, stained with 0.4% sulforhodamine B (SRB) for 4 h at room temperature, rinsed with 1% acetic acid and allowed to dry overnight [36]. The resulting coloured residue was dissolved in 200 ml Tris base (10 mM, pH 10.0) and optical density was recorded at 490 nm using a microplate reader ELx808 (BioTek Instruments). The results were analyzed by Graph Pad Prism (Graph Pad Software, Inc., San Diego, CA) and the sigmoidal dose response curve was used to determine 50% cell growth inhibitory concentration (IC50). The growth inhibition assay was performed once in triplicate.

4.4. Antibacterial assay The antibacterial screening was performed using the agar welldiffusion method [37].

Acknowledgements Mr. Hizbullah khan is highly grateful to Higher Education Commission (HEC) of Pakistan for providing PhD scholarship under the “5000 Indigenous PhD Scholarships Programme”, at Quaid-iAzam University Islamabad and six months scholarship under the programme of International Research Support Initiative Programme (IRSIP) as a Graduate Research Trainee at Department of Chemistry, McGill University, Montreal, Quebec, Canada.

Appendix. Supplementary material The crystallographic data for the structural analyses of complexes 1 and 2, have been deposited with the Cambridge Crystallographic Data Centre, CCDC No. for 1 is 812154 and for complex 2 is 812155. Copy of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge, CBZ 1EZ, UK (fax: þ44 1223 336 033; email: [email protected] or www: http://www.ccdc.cam.ac.uk).

4077

References [1] M. Shaharyar, M.M. Abdullah, M.A. Bakht, J. Majeed, Eur. J. Med. Chem. 45 (2010) 114e119. [2] American Cancer Society, in American Cancer Society Statistics For 2007, http://www.cancer.org/docroot/PRO/content/PRO_1_1_Cancer_Statistics_ 2007_Presentation.asp. [3] R. Palchaudhuri, V. Nesterenko, P.J. Hergenrother, J. Am. Chem. Soc. 130 (2008) 10274e10281. [4] K.S. Lovejoy, S.J. Lippard, Dalton Trans. 48 (2009) 10651e10659. [5] Y. Kasherman, S. Sturup, D. Gibson, J. Med. Chem. 52 (2009) 4319e4328. [6] T. Tsubomura, M. Ogawa, S. Yano, K. Kobayashi, T. Sakurai, S. Yoshikawa, Inorg. Chem. 29 (1990) 2622e2626. [7] J.D. Aguirre, A.M.A. Boza, A. Chouai, J.P. Pellois, C. Turro, K.R. Dunbar, J. Am. Chem. Soc. 131 (2009) 11353e11360. [8] J. Gao, Y.G. Liu, R.A. Zingaro, Chem. Res. Toxicol. 22 (2009) 1705e1712. [9] Z. Xue, M. Lin, J. Zhu, J. Zhang, Y. Lia, Z. Guo, Chem. Commun. 46 (2010) 1212e1214. [10] T. Boulikas, M. Vougiouka, Oncol. Rep. 10 (2003) 1663e1682. [11] E. Wong, C.M. Giandomenico, Chem. Rev. 99 (1999) 2451e2466. [12] M. Galanski, V.B. Arion, M.A. Jakupec, B.K. Keppler, Curr. Pharm. Des 9 (2003) 2078e2089. [13] T. Tanaka, K. Yukawa, N. Umesaki, Oncol. Rep. 14 (2005) 1365e1369. [14] D. Wang, S.J. Lippard, Nat. Rev. Drug Discov. 4 (2005) 307e320. [15] S.J. Berners-Price, T.G. Appleton, in: L.R. Kelland, N. Farrell (Eds.), Platinumbased Drugs in Cancer Therapy, Humana Press, Totowa, NJ, 2000, pp. 3e31. [16] Y. Jung, S.J. Lippard, Chem. Rev. 107 (2007) 1387e1407. [17] J.K. Barnham, M.I. Djuran, P.S. Murdoch, J.D. Ranford, P.J. Sadler, Inorg. Chem. 35 (1996) 1065e1072. [18] T. Rau, R. Van Eldik, in: A. Sigel, H. Sigel (Eds.), Metal Ions in Biological Systems, vol. 31, M. Dekker, New York, 1996, pp. 339e378. [19] W. Micklitz, W.S. Sheldrick, B. Lippert, Inorg. Chem. 29 (1990) 211e216. [20] K.J. Barnham, C.J. Bauer, M.I. Djuran, M.A. Mazid, T. Rau, P.J. Sadler, Inorg. Chem. 34 (1995) 2826e2832. [21] W.Z. Shen, D. Gupta, B. Lippert, Inorg. Chem. 44 (2005) 8249e8258. [22] E.J. Gao, F.C. Liu, M.C. Zhu, L. Wang, Y. Huang, H.Y. Liu, S. Ma, Q.Z. Shi, N. Wang, Enzym. Inhib. Med. Chem. 25 (2010) 1e8. [23] E.J. Gao, L. Wang, M.C. Zhu, L. Liu, W.Z. Zhang, Eur. J. Med. Chem. 45 (2010) 311e316. [24] B. Elzbieta, M. Magdalena, L. Ingo-Peter, M. Peter, A.K. Renata, P. Piotr, K. Urszula, R.J. Marek, Inorg. Chem. 45 (2006) 9688e9695. [25] H.A. Ewais, M. Taha, H.N. Salm, J. Chem. Eng. Data 55 (2010) 754e758. [26] M.P. Hacker, E.B. Douple, I.H. Krakoff, in: M.A. Nijhoff (Ed.), Platinum Coordination Complexes in Cancer Chemotherapy (1984), p. 267 Boston. [27] V. Alverdi, L. Giovagnini, C. Marzano, R. Seraglia, F. Bettio, R. S.SitranGraziani, D. Fregona, J. Inorg. Biochem. 98 (2004) 1117e1128. [28] G. Hogarth, E.J.C. Richards, C.R. Rainford-Brent, S.E. Kabir, I. Richards, J.D.E.T. Wilton-Ely, Q. Zhang, Inorg. Chim. Acta 362 (2009) 2020e2026. [29] D.L. Bodenner, P.C. Dedon, P.C. Keng, R. Borch, Cancer Res. 46 (1986) 2745e2750. [30] J.J. Criado, J.A.L. Aria, B. Marcias, L.R.F. Lago, Inorg. Chim. Acta 193 (1992) 229e233. [31] M. Castillo, J.J. Criado, B. Marcias, M.V. Vaquero, Inorg. Chim. Acta 124 (1986) 127e132. [32] F. Shaheen, A. Badshah, M. Gielen, G. Croce, U. Florke, D.D. Vos, S. Ali, J. Organomet. Chem. 695 (2010) 315e322. [33] F.H. Allen, O. Kennard, D.G. Watson, L. Brammer, A.G. Orpen, R. Taylor, J. Chem. Soc. Perkin Trans. 2 (1987) S1eS19. [34] R.M.C. Cattaneo-Pangrazzi, H. Schott, R.A. Schwendener, The Prostate 45 (2000) 8e18. [35] X. Area, Stoe, Cie, Darmstadt (2006). [36] P. Skehan, R. Storeng, D. Scudiero, A. Monks, J. McMahon, D. Vistica, J.T. Warren, H. Bokesch, S. Kenney, Michael R. Boyd, J. Natl. Cancer Inst. 82 (1990) 1107e1112. [37] A. Rahman, M.I. Choudhary, W.J. Thomsen, In Bioassay Techniques for Drug Development. Harward Academic Press, Amsterdam, 2001.