Keggin-type polyoxometalate 1: 1 complexes of Pb(II) and Bi(III): experimental, theoretical and luminescence studies

Bi3+ and Pb2+ uptake by a monolacunary Keggin-type [PW11O39](7-) anion leads to the formation of [PW11O39Bi](4-) and [PW11O39Pb](5-) complexes with a stereochemically active lone pair at the incorporated heterometal. The two complexes were isolated as (TBA)(4)[PW11O39Bi] (1) and (TBA)(5)[PW11O39Pb] (2) and characterized by P-31 and W-183 NMR spectroscopy, high-resolution electrospray mass-spectrometry (HR-ESI-MS) and cyclic voltammetry (CV). EXAFS and XANES data confirm the unchanged oxidation state and psi-square pyramidal geometry of Bi3+ and Pb2+ in 1 and 2. DFT calculations were used in order to (i) confirm the absence of ligands attached to the heterometal sites in both complexes and localize the lone pair, and (ii) assign all signals in the W-183 NMR spectra. Complexes 1 and 2 demonstrate photoluminescence (PL). A reversible change in the PL spectra of both complexes in the presence of water vapor has been detected. On the contrary, PL data for sandwich-type ((CH3)(4)N)(4)K-3[H-4(PW11O39)(2)Bi]center dot 25H(2)O (3) do not show sensitivity to water vapor.

Automated summary

The study found that Bi3+ and Pb2+ form stable complexes with [PW11O39](7-) anions, exhibiting stereochemically active lone pairs. Characterization revealed specific oxidation states and geometries for these complexes, along with photoluminescent properties.