Controlling the Self‐Assembly of a Mixed‐Metal Mo/V–Selenite Family of Polyoxometalates

Abstract Five mixed‐metal mixed‐valence Mo/V polyoxoanions, templated by the pyramidal SeO 3 2− heteroanion have been isolated: K 10 [Mo VI 12 V V 10 O 58 (SeO 3 ) 8 ]⋅18 H 2 O ( 1 ), K 7 [Mo VI 11 V V 5 V IV 2 O 52 (SeO 3 )]⋅31 H 2 O ( 2 ), (NH 4 ) 7 K 3 [Mo VI 11 V V 5 V IV 2 O 52 (SeO 3 )(Mo V 6 V V ‐ O 22 )]⋅40 H 2 O ( 3 ), (NH 4 ) 19 K 3 [Mo VI 20 V V 12 V IV 4 O 99 (SeO 3 ) 10 ]⋅36 H 2 O ( 4 ) and [Na 3 (H 2 O) 5 {Mo 18− x V x O 52 (SeO 3 )} {Mo 9− y V y O 24 (SeO 3 ) 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 η,μ and μ,μ 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.