Dithallium(III)-Containing 30-Tungsto-4-phosphate, [Tl 2 Na 2 (H 2 O) 2 (P 2 W 15 O 56 ) 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 [Tl ₂ Na ₂ (H ₂ O) ₂ {P ₂ W ₁₅ O ₅₆ } ₂ ] ^16- (1) by a multitude of solid-state and solution techniques. Polyanion 1 comprises two octahedrally coordinated Tl ³⁺ ions sandwiched between two trilacunary {P ₂ W ₁₅ } 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 ³¹ P and ^203/205 Tl NMR. This was also supported by Tl NMR spectra simulations including several spin systems of isotopologues with half-spin nuclei ( ²⁰³ Tl, ²⁰⁵ Tl, ³¹ P, ¹⁸³ W). ²³ Na NMR showed a time-averaged signal of the Na ⁺ counter cations and the structurally bonded Na ⁺ ions. ^203/205 Tl NMR spectra also showed a minor signal tentatively attributed to the trithallium-containing derivative [Tl ₃ Na(H ₂ O) ₂ (P ₂ W ₁₅ O ₅₆ ) ₂ ] ^14- , which could also be identified in the solid state by single-crystal X-ray diffraction. The bioactivity of polyanion 1 was also tested against bacteria and Leishmania.