Controlling the self-assembly of a mixed-metal Mo/V-selenite family of polyoxometalates

Five mixed-metal mixed-valence Mo/V polyoxoanions, templated by the pyramidal SeO32- heteroanion have been isolated: K10MoVI12VV10O58(SeO3)8]center dot 18?H2O (1), K7MoVI11VV5VIV2O52(SeO3)]center dot 31?H2O (2), (NH4)7K3MoVI11VV5VIV2O52(SeO3)(MoV6VV- O22)]center dot 40?H2O (3), (NH4)19K3MoVI20VV12VIV4O99(SeO3)10]center dot 36?H2O (4) and Na3(H2O)5{Mo18-xVxO52(SeO3)} {Mo9-yVyO24(SeO3)4}] (5). All five compounds were characterised by single-crystal X-ray structure analysis, TGA, UV/Vis and FT-IR spectroscopy, redox titrations, and elemental and flame atomic absorption spectroscopy (FAAS) analysis. X-ray studies revealed two novel coordination modes for the selenite anion in compounds 1 and 4 showing eta,mu and mu,mu coordination motifs. Compounds 1 and 2 were characterised in solution by using high-resolution ESI-MS. The ESI-MS spectra of these compounds revealed characteristic patterns showing distribution envelopes corresponding to 2- and 3- anionic charge states. Also, the isolation of these compounds shows that it may be possible to direct the self-assembly process of the mixed-metal systems by controlling the interplay between the cation shrink-wrapping effect, the non-conventional geometry of the selenite anion and fine adjustment of the experimental variables. Also a detailed IR spectroscopic analysis unveiled a simple way to identify the type of coordination mode of the selenite anions present in POM-based architectures

Assembly of a family of mixed metal {Mo : V} polyoxometalates templated by TeO₃^2-: {Mo₁₂V₁₂Te₃}, {Mo₁₂V₁₂Te₂} and {Mo₁₇V₈Te}

The influence of the pyramidal heteroanion, TeO<sub>3</sub><sup>2−</sup> in the self-assembly of mixed metal (Mo/V) systems, is demonstrated by the isolation of three novel mixed-metal, mixed-valence architectures, {Mo<sub>12</sub>V<sub>12</sub>Te<sub>3</sub>} (<b>1</b>), {Mo<sub>12</sub>V<sub>12</sub>Te<sub>2</sub>} (<b>2</b>) and {Mo<sub>17</sub>V<sub>8</sub>Te} (<b>3</b>) with the tellurium centres exhibiting the novel µ8-TeO4 and µ9-TeO<sub>3</sub> coordination modes while compounds 1 and 2 were discovered utilizing ESI mass spectrometry