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Synthesis and Characterizationof Organotin SubstitutedHeteropolytungstophosphates and TheirBiological ActivityXiao Hong Wang a & Jing Fu Liu aa Department of Chemistry , Northeast Normal University , Changchun,130024, P.R. ChinaPublished online: 05 Oct 2006.

To cite this article: Xiao Hong Wang & Jing Fu Liu (2000) Synthesis and Characterization of OrganotinSubstituted Heteropolytungstophosphates and Their Biological Activity, Journal of Coordination Chemistry,51:1, 73-82, DOI: 10.1080/00958970008047080

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SYNTHESIS AND CHARACTERIZATION OF ORGANOTIN SUBSTITUTED

HETEROPOLYTUNGSTOPHOSPHATES AND THEIR BIOLOGICAL ACTIVITY

XIAO HONG WANG and JING FU LIU*

Department of Chemistry, Northeast Normal University, Changchun 130024, P.R. China

(Received 16 March 1999; In fd form 22 July 1999)

Organotin-substituted Keggin or Dawson tungstophosphates [(CH@OCCHzCHzSn),- (pW90~)2p-, [ ( ~ ~ ~ H z C H Z S ~ ) P W I I O ~ $ - , [ ( ~ , ~ H z C H z ~ ) P z w i ~ 6 i ~ ' - ,

[(CH@OCCH(CH~)CHzSn)PzWl~sl]7- have bcen prepared by reactions of the pmethoxy- carbonylcthyltin, ~mdhoxycarbonyl-~-propyltin txichlorides with PW&, PW 110; and P ~ W I ~ O : ~ , rcspcdvcly. The producta were isolated as K+, and BU*N+ salts, and wen char- actcrk l by means of elemental analysis, IR 'H NMR, '% NMR and "'Sn NMR spectra, and polaropphy. The antitumour activity of the complwar as investigated and the effect of the polyanions and estertin on antitumour activity was examined.

Keywords: Antitumour activity; Organotiq Keggin structun; D a m n structure; synthesis

[ ( C H ~ ~ ~ C C H ( ( = H ~ ~ Z S ~ ) ~ ~ W ~ ~ - . [(CIWOCCH(CH~)CHZS~)~W~ 10d- and

INTRODUCTION

Current interest in polyoxometallates (POMs) is driven by the potential application of these complexes in areas of catalysis, medicine and materials science.'*2 It has been recognized for some time that the,versatility of the polyoxometallates and their catalytic applications can be significantly increased by grafting organic and organometallic groups onto the poly- oxometallate surface.

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14 X.H. WANG AND J.F. LIU

The reactivity of mono- and polyvacant polytungstates with organotin was systematically investigated by P ~ p e ~ - ~ and Knoth?-” In order to develop the application of organometallo derivatives of polymetallates in medicine, our group has systematically investigated the synthesis of organo- tin, organotitanium and organozirconium complexes, and their antitumor activity.” Here we report the synthesis and characterization of estertin sub- stituted heteropolytungstophosphates derived from the lacunar species PWgOG, PW110;;, and P2W170:?-, and their antitumour activity.

EXPERIMENTAL

Preparation of Compomds

All the reagents were of analytical or guaranteed quality. The compounds ,0-CH300CCH2CH2SnCl3 and ,&CH300CCH(CH3)CH2SnC13 were pre- pared following Ref. [I31 and identified by ‘H NMR. N~~H[A-PW~OM] - 24H20I4 (noted as PW9), Na7PW11039’5 (noted as PWII), K]&W1706]- 1 5H20I6 (noted as P2W17) were prepared following the published methods and were identified by polarography.

K~HS[(CH~OOCCH~CH~,S~)~(P W9034)2] - Z3HzO

To a solution of 0.94 g (3 mmol) of CH300CCH2CH&C13 in 40 ml of H2O was added sodium acetate to adjust the pH to 1.6. Then, 2.8 g (1 -01) of NasH[PW90%] - 24H20 was quickly added with stirring. Within a few sec- onds, most of the tungstophosphate dissolved and the solution turned clear. The solution was stirred for 10min and filtered. KC1 was added to the fil- trate until no more precipitate formed. The precipitate was filtered and recrystallized from hot water (yield 1.3g). Analytical data are summarized in Table I.

K 4 (CH3OOCCHzCH&a)P W1&91 - I2HzO

To a solution of 0.32 g (1 mmol) of CH300CCH2CH2SnC13 in 40 cm3 of H2O was added sodium acetate to adjust the pH to 1.6, then 2.8 g, 1 mmol Na7PW11039 was added in small portions with stirring. The acidity of the mixture was adjusted to pH 6-6.5 with sodium acetate and stirred at 80°C for 30min. After filtration, KCl was added until no more precipitation was observed. The white precipitate was filtered and recrystallized from hot water, yield 1.1 g.

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TABL

E I

Ana

lytic

al d

ata

for s

alts

of H

PA

&H

d(c4

Hfi2

sn)3

*@w

9M

6.53(

6.54)

62

.1 l(6

0.36

) 1.

3q1.

13)

2.87(

2.86)

4.

2q4.

29)

2.49(

2.64)

0.4

5(0.4

8)

U(C

JbW

WW

1d

3.9

2(3.9

2)

65.23

(66.4

1)

0.89(

1.02

) 5.4

1 (5.1

5)

8.3q

8.32

) 1.3

3( 1.

40)

0.19

(0.2

3)

W~

(W

~O

ZS

~)

P~

WI

~I

2.5q

2.53

) 65

.1q6

6.02

) 1.1

9(1.3

2)

3.29(

3.31)

4.

21(4

.20)

l.O

l(1.0

2)

0.18(

0.21)

.13H

20

* lW

20

* ll

H20

(B

uNjj

H~K

C&

Ofi

n)p(

pW~)

d 3.

w3.

94)

54.w54.46)

l.OO

(1.03

) - 1H

20

* 2H

2O

(Bu*

"(C

IHPD

n)PW

i 11

3.

W3.

10)

50.1

l(52.

39)

0.77(

0.81)

(Bu*

N)*H

3[(C

4H,O

2Sn)

P2W

17]

2.w

2.22

) SS

.OO

(58.1

9)

0.50

(0.5

8)

.lH

?O

14.9

7(15

.08)

0.9

1(0.9

1)

2.8q

2.81

)

21.3

5(21

.24)

1.

45( 1

.46)

3.8q

3.85

)

15.21

(15.

26)

l.OO

(1.05

) 2.8

7(2.8

8)

K*

Hi(

~5

~~

2~

n)~

(pw

,hl

6.5q

6.51

) 60

.00(

60.1

0)

1.2q

1.13

) 2.

87(2

.85)

3.9

243.9

4)

3.18(

3.28)

0.3

4(0.3

6)

U(C

~H

~O

~S

~)P

WI

11.1

3H20

3.8

7(3.9

1)

64.2

7(66

.13)

O

.W(l.

02)

5.00(

5.12)

7.

65(7

.69)

1.

8q1.

83)

0.17

(0.1

6)

* 1

w2

0

-1lH

fl

&H

~(C

~H

&S

~)P

~W

I 71

2.

w2.

52)

66.11

(65.8

3)

l.ll(1

.31)

3.

28(3

.30)

4.

2q4.

19)

1.29

(1.2

7)

0.1q

o.17

)

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76 X.H. WANG AND J.F. L N

&H~[(CH~OOCCH~CH~tt) Pz W I @ ~ I ] 1lHzO

&H3[(CH300CCH2CH2Sn)P2WI7O61] - 1 lH20 was prepared analogously. After adjustment of the pH of the solution, 0.32g (1 mmol) of CH300CCH2CH2SnCl3 and 4.8 g (1 mmol) of &&W17061] - 15H2O was added. The final pH was adjusted to 4.7 with potassium acetate. The solu- tion was stirred at 80°C for 30 min. After filtration, the solution was evapo- rated to dryness. The white potassium salt was recrystallized from hot water.

Synthetic procedures for all the CH300CCH(CH3)CH2Sn substituted heteropolytungstophosphate potassium salts were analogous, except that CH300CCH(CH3)CHzSnC13 was used in place of CH300CCH2CH2SnC13.

The B&N+ salts of the title complexes were prepared similarly but pow- dered (BQN) Br was added to the filtrate for crystallization of the product. Recrystallization from hot CH3CN gave white powders.

Antitumor Activity of POMs

The antitumor activity of POMs on two human cancer cell lines was tested by the MTT experiment described below.

MTT is 3-[4,5-dimethylthial-2-yl]-2,5-diphenyltetrazolium bromide, also named thiazolyl blue. It is a dye which can accept an H atom. Surviving tumor cells can reduce the yellow MTT to insoluble blue formazan, but dead tumor cells do not possess this capability. The formazan is dissolved by DMSO, then determined colorimetrically with a microplate reader (490 mm), that examined cell survival rate.

Subcultured Hela cells and SSMC-7721 cells were suspended in 0.25% trypsin. The cell suspension (1 x 105-106 cells~rn-~) was added to a 96-well plate at loo@ per well, then incubated at 37°C in 5% C02 for 24h. Then 100 pl samples containing POM was added. After 72 h, 20 pl of M'IT (5 mg

in 0.01 M PBS) was added. The mixture was incubated for 4 h. The supernatant was removed, then DMSO (1 50 pl) was added. The mixture was shaken for lOmin at room temperature. Colorimeter analysis was deter- mined with a microplate reader (490nm), effective cell 50% lethal con- centrations (ICm) was calculated by statistical methods.

Analytical Methods

W, P and Sn were determined by ICP - AES. The H2O content was deter- mined by thermogravimetry. C, H and N were determined using a PE-2400 analyser. K was determined by atomic absorption spectroscopy (Table I).

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HETEROPOLYTUNGSTOPHOSPHATES 77

"'Sn and lS3W NMR spectra were recorded at 16.6MHz on a U n i t y 4 spectrometer. Chemical shifts are referenced to Na2W04 for "'W. For '19Sn, the chemical shifts are referenced to (CH3)4Sn. 'H NMR spectra were recorded on Brucker AC-80 spectrometer. IR spectra were recorded on an Alpha Centauri FTIR spectrometer

(4000-200cm-') using KBr pellets. Polarograms were obtained using a 3848 Polarographic Analyser, equipped with 303A type electrodes.

RESULTS AND DISCUSSION

Spectra

Observed frequencies and tentative assignments of the main IR and W bands of the title complexes are given in Table 11. IR spectra of organotin-substituted heteropolyanions exhibit the follow-

ing characteristics. The IR spectra of all the complexes exhibit the four char- acteristic W-Od (tenninal oxygen), W-%-W (bridging oxygen), W-0,-W (bridging oxygen) and P-0, (central oxygen) asymmetric stretching vibra- tional peaks for heteropolyanions with Keggin or Dawson structure, sug- gesting that the title complexes have the Keggin or Dawson structure. Replacement of RSn3+ in the polyanions causes a vibrational red shift in comparison with PW12Ok or P2W180&, due to an increase in negative charge on the polyanion. This result is consistent with other mixed-type polyanions.'6 The P-0, bond vibrations of (RSn)3(PW& split. This fact demonstrates that the [RSn]'+ did not occupy the three vacant sites of the PWg anions to give (RSn)3PWg. The IR spectrum is similar to that of C O ~ ( P W ~ ) ~ . ' ~ This is because of the fact that if [RSnI3+ groups occupy the three vacant sites, it maintains the Kegsin structure and the PO4 asymmetric

TABLE I1 IR data (an-') and W maxima (nm)

Anions "U(w-Q) ""(w-ob-w) "up-4-w) " u ( P - 4 ) "c-0 LU (C&02S&(PW9)2 949 88 1 805 1050,1078,1100 1742 200,260 (c4Hfl2sn)pw11 950 88 1 806 1048,1099 1742 199.261 (c~f l2sn)PZwI7 950 909 784 1013,1091 1735 254,276 (cSH9%~)3(Pw9)2 948 88 1 805 1051,1078,1101 1740 201,260 ~~SHs02Sn)PWl1 951 88 1 802 1049,1099 1735 199,260 (c5%~2~~)p2w17 952 909 783 1014,1092 1735 255,276 a-pzw,s 966 916 792 1090,1022 256,277 a-pw12 995 900 805 1081 265 CH300CCH2CH2SnC13 1665 CH@OCCH(CH& 1660 CH2SnCl3

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78 X.H. WANG AND J.F. LIU

stretch is a single peak. In comparison with the P-0, bond vibration fre- quency of PzW18, that of (RSn)P2W17 changes little. This demonstrates that the RSn3+ group Occupies the vacant site of P2W17. In comparison with estertin, the C=O frequencies increase. The structure of p-methoxy- carbonylethyltin trichloride can be represented as

and the carbonyl stretching frequency is 1665cm-'. When ,!3-methoxy- carbonylethyltin reacts with HPA, the intramolecular carbonyl coordina- tion to Sn is broken and Sn incorporates terminal 0 atoms of HPA. The C=O vibration increases to 1735-1742cm-'.

All the complexes are colourless, so the spectroscopic region of interest is in the near W from 200 to 300nm. In this range all Keggin complexes exhibited two strong charge transfer (ct) absorption at cu. 200 and 260nm. The first results from the transfer od-w and the second (from O&, + w> is the characteristic band of PWlz polyanions with the Keggin structure." In comparison with a-P2Wls, P2W17(RSn) anions also exhibited two char- acteristic charge transfer bands at cu. 250 and 270 nm of the Dawson anion, indicating that (RSn)P2W17 anions have Dawson structure. The intense absorption band at cu. 270 nm has been attributed to a Ob/Oc + W ct band and the higher energy band to a o d -t W ct.

NMR Spectra

'HNMR and lS3WNMR data are listed in Table 111. Spectra of the title complexes are different from that of p-methoxycarbonylethyltin

TABLE In '*%VNMR' and 'H NMRb data (ppm)

Aniom 6

( C I O ~ H ~ S ~ ) ~ P W ~ ) ~ - l22.9( l)', -201.6(2) 3.72(s) 3.01(t) 1.66(t) ( C ~ O ~ H ~ S ~ ) P W I I -76.9(2), -91.5(2), -1 13.6(2) 3.84(s) 3.01(t) 1.73(t)

(C4Hp2sn)ptW17 -92.7, -96.3, -103.6 3.8I(s) 2.97(t) 1.78(t) -130.7(1), -166.1(2), -174.7(2)

-111.5, -120.6, -147.9 -115.8, -194.4, -209.9

GH702SnCh 3.94(s) 2.94(t) 2.22(t)

' BkN d t s dimlvcd in CH$N. Pougium d t s dissolved in D20. ' Relative intensity in parmthm.

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HETEROFQLYTUNGSTOPHOSPHATES 19

trichlorides. In CH3OOCCH2CH2SnCl3, the Sn atom links with three chloride atoms and the hydrogen chemical shift of SnCH2 is 2.22ppm. In (CH300CCH2CH2Sn)3(PW9)2, the electron density on Sn increases, so SnCH2 moves to higher field. This demonstrates that the [RSn]'+ group is incorporatad with the tungstophosphate and organic group did not separate from the Sn atom.

The '19Sn NMR spectiurn of (CH300CCH2CH2Sn)3(PW9)2 gives only a single line, implying that the tin environments are equivalent. The chemical shift of Sn is -578.6ppm, while (Ph)& is at cu. -128.1 ppm. Such a shift can be explained in terms of an increase in the electron density on the Sn atom when the [RSnI3+ groups incorporate to form six-coordinate Sn corn pound^.'^

The IE3W NMR spectrum of (CH~OOCCH~CH&)~(PW~)Z consists of two lines with intensity ratio 1 : 2, indicating that there are two non-equiva- lent tungsten environments in the heteropolyanion. According to lE3W NMR patterns of trisubstituted heteropolyanions summarized by Pope,' the lE3W NMR of sandwiched structures show two lines with intensity ratio 1 : 2. This fact supports the stoichiometry of the new heteropolyanion, and demonstrates that (CH300CCH2CH&),(PW9)2 has nominal D3h

symmetry containing three [(CH300CCH2CH2)SnI3+ groups sandwiched between two A-PW9 anions.

The lE3W NMR of (CH300CCH2CH2Sn)PW11 confirms the incorpora- tion of the [RSnI3+ group in the polyoxoanion. Since the mono-substituted a-Keggin derivative displays the anticipated C, structure, six resonances would be expected. The '*%NMR spectrum of (CH300CCH2CH2Sn) PWll gives six lines with intensity ratio 2:2:2: 1:2:2, implying that (CH300CCH2CH2Sn)PW1 1 retains the a-Keggin structure.

The lE3W NMR spectrum of (CH300CCH2CH2Sn)P2W17, in agreement with C, symmetry, shows nine lines, similar to the case of a2-P2Wl,. This (CH300CCH2CH2Sn)P2W 1 retains the Dawson structure.

"P NMR of the (CH300CCH2CH2Sn)3(PW9)2 gives only one line with a chemical shift of -8.34ppm, showing that the environments of the two phosphorus atoms are equivalent, and also demonstrating that the PW9 unit in the (RSn)3(PW9)2 is an A-type isomer in line With the results of Knoth."

POlnrogrPphY

El,, values were determined at 298 K in 0.5 moI acetate buffer solution with saturated calomel and dropping mercury electrodes. Ell2 data of the title complexes are given in Table IV. Reduction processes involved the

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TABLE IV Half-wave potentials (V) of the title anions at different pH values

Anwns PH

(C4H702Sn)302 ww-wv -0.868(4) -0.900(4) ( C ~ H 9 0 2 W 3 0 2 wm-wv -0.840(4) -0.872(4) (C4Hf12Sn)mI 1 ww-wv -0.466(2) -0.528(2)

-0.676(2) -0.788(2) ( C ~ H ~ O ~ S ~ ) P W I I ww-wv -0.600(2) -0.7842)

-0.712(2) -0.940(2) ( C ~ H ~ O ~ S ~ ) P ~ W I ~ ww-wv -0.601(2) -0.7242)

-0.8 14(2) -0.948(2)

(CSHPOZS~)P~WI~ ww-wv -0.40 l(2) -0.524(2) -0.576(2) -0.660(2) -0.811(2) -0.900(2)

-0.9344) -0.909(4) -0.699(2) -0.898(2) -0.900(2) -1.112(2) -0.693(2) -0.876(2) -1.111(2) -0.654(2) -0.783(2) -1.098(2)

TABLE V Inhibitory effect of the title complex on some cells in vitro

Compfexes Tumor cefk Dose (pg ml-') Inhibitory ICm* (pgml-*) rate (%)

Hela

SSMG7721

Hela

SSMC-7721

Hela

SSMC-7721

Hela

SSMC-7721

Hela

SSMC-7721

Hela

SSMG7721

100

10 100

10 100

10 100

10 100

10 100

10 100

10 100

10 100

10 100

10 100

10 100

10

100

10.2 100

11.1 100

11.6 100

12.4 59.2

5.9 71.2

7.0 59.7

6 73.4

7.3 55.3

5.2 56.9

5.6 56.6

5.4 61.9

6.2

49.9

47.6

45.1

40.3

82.6

70.1

82.0

68.3

90.2

86.3

86.7

79.1

~~

*The 50% inhibitory concentration (I&) ir defied an the concentration which mpprwa growth of tumour d k by 50%.

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HETEROFOLYTLJNGSTOPHOSPHATES 81

reduction of tungsten and showed pHdependent peaks, implying that reduction accompanied by protonation. The reduction of WM of (RSn)3(PW9)2 shows an apparent one-step four electrons reduction peak. A straight line is obtained by logarithmic analysis of the polarographic wave. The number of electrons involved can be calculated from the slope of the line. This should allow one to discriminate between a- and /%isomers. For XWg (X = P, Si, As), the reduction of a-XWgl* is an apparent one-step four electron reduction and for /?-XWg is a two-step two electron reduction process. Thus (RSn)3 (PW9)z anions are a-isomers. The polarographic waves for (RSn)P2WI7 are expected three. (CH300CCH2CH2Sn)P2W l7 at pH = 4.2,4.7 show only two reduction peaks because of overlap.

Antiturnour Activity

The data summarized in Table V show that the title complexes display inhibitory action to Hela and SSMC-7721 tumour cells. The antitumor activity of tri-substituted compounds is higher than of mono-substituted compounds. We think that the centre of antitumor activity is the Sn atom. Because the Sn content of (RSLI)~(PW~)~ is more than in monosubstituted compounds, the same dosage gives a greater inhibitory rate. The influence of different organotin group on antitumor activity is small.

Acknowledgements

The support of National Nature Science Foundation is gratefully acknowledged.

References

[l] D.E. Katsoulis, Chem. Rev., 98,359 (1998). [2] J.T. Rhulc, C.L. Hill and D.A. Judd, Chem. Rev., 98,327 (1998). [3] F. ZoMOcVijlle and M.T. Pope, J. Am. Chcm. Soc., 101,221 1 (1979). [4] F.B. Xin and M.T. Pope. Znorg. Chem., 35,5693 (1996). [q F.B. Xin, M.T. Pope, G.J. Long and U. Russo, Znorg. Chem., 35,1207 (1996). [6] F.B. Xin and M.T. Pope, Orgunomerallics, 13,4881 (1994). [7'J W.H. Knoth, J. Am. Chem. Soc., 101,759 (1979). [8] W.H. Knoth, J. Am. C h . Soc., 101,221 1 (1979). [9] W.H. Knoth, P.J. D d c and R.D. Farla, Orgunometdlics, 4.32 (1985). [lo] W.H. Knoth, PJ. Domaillc and D.C. Roe, Znorg. Chem., 22,198 (1983). [11] P.J. Domaille and W.H. Knoth, Znorg. Chem., 22,818 (1983). [12] Q.H. Yang, H.C. Dai and J.F. Liu, Truns. Merd Chem.. 23.93 (1998). [13] R.E. Huttcn, J.W. Burloy and V. O W , J. Orgunomerallic Chem., 156,369 (1978). [14] R. Massart, R. Contarit, J.M. Fruchart, J.D. Ciabrini and M. Foumier. Znorg. Chem., 16,

[15] A. Tezc and G. Hme, Inorg. Synrh., 27,87 (1992). 2916(1977).

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82 X.H. WANG AND J.F. LIU

[ lq M. Lu and J.F. Liu, Pofyhedron., 14,2127 (1995). [17] W.H. Goth,P.J.DomaiUeandR.L. €Iarlow,Inmg. Chem.,25,1577(1986). [18] M.T. Pop and A. Mullcr, Angew. Chem. Znt. Ed. Engl., 3,263 (1993). [19] J. Holacek, M. Nadvomik and K. Handlir, J. Organometdlic Chem., 241.177 (1983). [20] W.H. Goth, P.J. Domaille and R.D. Farlee, Orgunomctallics, 4.62 (1985).

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