Synthesis and Biological Activity of Organothiophosphoryl Polyoxotungstates

Organothiophosphoryl polyoxotungstates R∋XW∞∞O∋∃/- , R∋ P∋W∞,O∞/-, R∋PW∃O∋ Δ-(X = P, Si, Ge, B or Ga; R = PhP(S), C6H11P(S)) have been prepared from lacunary polyoxoanions and PhP(S). The products were characterized by elemental analysis, IR, and NMR spectroscopy. According to spectroscopic observations, the hybrid anions consist of a lacunary anion framework on which are grafted two equivalent or groups through P-O-W bridges. Some of the title compounds showed the antigerm activity.


I.INTRODUCTION
Polyoxometalates (POMs) are early transition metal oxygen anion clusters. Only more recently have some of the biological and pharmacologic properties of POMs been investigated tll. The principal advantageous feature of POMs is that nearly every molecular property that impacts the recognition and reactivity of POMs with target biological macromolecules can be altered. Pendent organic biological groups could be used to increase recognition of key substructures in target biomacromolecules, and enhance the facility of drug formulation. The reactivity of lacunary polyoxometalates with organic and organometallic groups has been summarized t21. To date, the reaction of lacunary polyoxotungstates with organophosphonic acid has been reported rarely, except for a unique study of Kim and Hill I31 on PhPO derivatives of monovacant tungstophosphate and -silicate, and Thoucenot on RPO derivatives of trivacant tungsto-phosphate and divacant tungsto-silicate [4]. There are only two or three papers involving the biological properties of POMs derivatized with organic groups. In order to develop this uncharted territory, we investigated the biological activity of the organotin, organotitanium and organophosphory polyoxotungstates t-81. We report herein the preparation and biological activity of organophosphoryl polyoxotungstates RzXWllO39 n', R2P2W170616and RzPW9034" (X=P, Si, Ge, B, Ga; R=PhP(S), C6HllP(S) ).

Material
All reagents were of analytical or guaranteed grade; MeCN was distilled over P20, and used immediately. PhP(S)CI2 and C6HIIP(S)CI2 were prepared following literature procedures [9,al. Na7PW1103913H20 [lr], [12] [12] [12] [111 K6Na2SiW11Oa913H20 K6Na2GeW1103913H20 K7NaBWllOa913HzO K9GaW11Oa913H20 K10P2W1706117H20 DE] and NasHPW903424H20 - [13] were prepared using procedures described in the K7NaHBWO3913H20 (1.59 g, 0.5 mmol) and Bu 4NBr (0.81 g, 2.5 mmol) were suspended in MeCN (25 ml), and an acetonitrile solution of PhP(S)CIz (1.0 mmol in 10 ml of MeCN) was added dropwise under vigorous stirring, and the mixture was stirred for 48 h at room temperature. After separation of a white solid, the resulting red solution was concentrated to ca. 10 ml in a rotary evaporator, and was tb.en diluted with 150 ml of absolute ethanol to produce a red brown precipitate. The red brown precipitate was isolated by filtration, and the solid isolated was reprecipited again from 5 ml of acetonitrile solution by adding 100 ml of absolute ethanol to give 1.31 g (67 %) red brown powder. Anal and an acetonitrile solution of PhP(S)CI2 (1 mmol in 15 ml of MeCN) was added dropwise under vigorous stirring, and the mixture was stirred for 48 h at room temperature. After separation of a white solid, the resulting solution was concentrated to Ca. 10 ml in a rotary evaporator, and was then diluted with 150 ml of anhydrous Et20 to produce an oily deposit. The turbid supernatant was decanted from the oily deposit, and the deposit was reprecipitated again from 5 ml of acetonitrile solution by adding 150 ml of Et20 to give 1.80 g (63 %) pale green powder. Anal stirring. The solution turned pale yellow, and mixture was stirred overnight under reflux. The solid was filtered off, the resulting blue solution was concentrated to 10 ml in a rotary evaporator, and anhydrous Et20 (150 ml) was added to produce a blue oily deposit. The turbid supernatant was decanted from the oily deposit, which was redissolved in MeCN (5 ml). This solution was then rediluted with Et20 (150 ml), and the pale blue sticky solid formed was crushed with a spatula until it became a powder. The solid was filtered off, washed with EtzO, and air-dried to give 1. 3  were referenced to 2M Na2WO4 in D20 for 83W. For 3p, the chemical shifts were given with respect tc external 85% H3PO4 in CD3CN. W, P, Si, Ge, Ga, and B contents were determined using a Leeman corporation inductively coupled plasma (ICP) emission spectrometer while C, H and N contents were determined using a PE-2400 analyser and K was determined by atomic absorption spectroscopy (PE-3030).

Biological activity studies
The antitumor activity of compounds was tested by the MTT experiment as previously described tsl.
The antigerrn activity of some compounds was tested using procedures described in literature [4. 3. RESULTS AND DISCUSSION 3.1 31p NMR spectra The 31p NMR spectra data for all compounds and several representative spectra are given in Table and Figure l, respectively. The attachment of thiophosphoryl groups onto the polyoxotungstates surface are demonstrated by the resonance in the 31p NMR spectra, which are all distinct from those of PhP(S)CIz or C6HIP(S)CI2 in the identical medium. The 31p NMR spectra of compounds 1, 6, 12 and 13 exhibit two lines with a relative intensity of 2:1, indicating that there are two nonequivalent phosphorus environments. The high-frequency resonances are attributed to the thiophosphoryl group, and the low-frequency single of relative intensity are assigned to the central PO4 unit of the polyoxotungstates portion. The relative intensity indicates a ratio of two RP(S) groups per polyoxometalate, which is consistent with the results of the chemical analysis.
Polyoxotungstates. As for the compounds derived from PzW1706110" anion, their 31p NMR spectra present three lines with a relative intensity ratio of 2:l'l, indicating that there are three non-equivalent phosphorus environments in the complexes. The high-frequency resonance is assigned to the organothiophosphoryl groups. The occurrence of two equal peaks in the low-frequency region shows that the half-anions of ot2-P2Wl7 are not identical. P (1) is the phosphorus atom closest to the site of substitution. P (2) is that remote from the substitution site. It is worth noting that the chemical shitt of the phosphorus atom of the unperturbed PW9 half-anion is practically constant; it does not depend upon any change (hole or substitution) that may occur in the other half-anion. The 31p NMR spectra of the title compounds show only single line at upfield, indicating that the model of attachment of two organic groups to the lacunary anions are equivalent. A heteropolyanion with a Keggin structure becomes the Cs lacunary polyanion XMllO39 atter losing one heavy atom and its terminal, which contains three W3013 triads and one W2O10 diad. These anions have a hole surrounded by five oxygen atoms, one Oa, two Ob and two Oc (see Fig.2). When two double-bonded phosphoryl groups each bridges two of the five oxygen atoms that define the hole in the lacunary polyanion, there are two possibilities, i.e. the groups can bridge the oxygens such that they are either unequivalent or equivalent. The single resonance in the NMR spectra indicates that the mode of attachment of the organic groups to the lacunary anion is equivalent, i.e. each organic group is connected to two W atoms belonging to a triad and a diad, respectively.
3.2 S3W NMR spectra The 183W NMR spectra of compounds 4, 11, 12, 13 and chemical shifts of some compounds are shown in Figure 3 and Table 2, respectively.  The S3W NMR spectra of compounds 12, 13 consist of five peaks of relative intensity 1:2:2:2:2. In the Well-Known Keggin structure, all the tungsten is identical as shown by a single resonance in the 83W NMR spectra. Removal of three WO6 groups reduces the symmetry of the anion from Td to C3v and the expected two-peak pattern is obtained in the 183W NMR spectrum. The five-line 83W NMR spectra of compounds indicate a lowering of the symmetry of the tungstophosphate framework from C3v to Cs through the attachment of organothiophosphoryl groups. This feature was observed for RPO derivatives of trivacant tungstophosphate t41. The lS3w NMR spectrum of compound 11 in CH3CN-CD3CN consists of nine peaks in the ratio 1:2:2:2:2:2:2:2:2. This pattern confirms a molecule of Cs symmetry as would be found by substitution in the "cap" position of the [_2-P2W17061] 10" isomer. 3.3 Biological activity of some of organophosphoryl polyoxotungstates Fusarium graminearum causing rice seedling blight and root rot was used in the antigerm activity experiments. The antigerm activity was tested by mycelia block method. Briefly, the test compounds were dissolved in DMSO and diluted to give 10, 20, 50 or 100 times solution, then were diluted with PDA medium to give a final concentration of 100, 50 or 20 ppm, respectively. The germ was incubated in PDA medium for Polyoxotungstates. one week, then the mycelia block with 6 mm of hole diameter were added to PDA culture medium contain various amounts of test compounds, and incubated for 8 days at 28 in an incubator. Every test was repeated three times. The antigerm effect of the compounds was judged by the size of diameter of mycelia block grown in medium of various compounds compared to the control. The diameter of mycelia block and inhibitory rate for some of organothiophosphoryl polyoxotungstates and together with compounds reported previously are listed in Table 3. The antitumor activity of some compounds was tested by the MTT method. The experimental results showed that the title compounds did not exhibit higher antitumor activity as indicated in Table 4.