Dithallium(III)-Containing 30-Tungsto-4-phosphate, [Tl2Na2(H2O)2(P2W15O56)2]16-: Synthesis, Structural Characterization, and Biological Studies

Here we report on the synthesis and structural characterization of the dithallium(III)-containing 30-tungsto-4-phosphate [Tl2Na2(H2O)(2){P2W15O56}(2)](16-) (1) by a multitude of solid-state and solution techniques. Polyanion 1 comprises two octahedrally coordinated Tl3+ ions sandwiched between two trilacunary {P2W15} Wells-Dawson fragments and represents only the second structurally characterized, discrete thallium-containing polyoxometalate to date. The two outer positions of the central rhombus are occupied by sodium ions. The title polyanion is solution-stable as shown by P-31 and Tl-203/205 NMR This was also supported by Tl NMR spectra simulations including several spin systems of isotopologues with half-spin nuclei (Tl-203, Tl-205, P-31, W-183). Na-23 NMR showed a time-averaged signal of the Na+ counter cations and the structurally bonded Na+ ions. Tl-203/205 NMR spectra also showed a minor signal tentatively attributed to the trithallium-containing derivative[Tl3Na(H2O)(2)(P2W15O56)(2)](14-), which could also be identified in the solid state by single-crystal X-ray diffraction. The bioactivity of polyanion I was also tested against bacteria and Leishmania.