Design, synthesis and excellent third-order NLO properties of two new polyoxometalates constructed from Keggin polyanions bonded by a solvent molecule

Abstract

Two new monosubstituted Keggin structural polyoxometalates [H₅PMo₁₁O₃₉Zn(C₅H₅N)]·(C₅H₅N)₅·H₂O (1) and [H₅PW₁₁O₃₉Co(C₅H₅N)]·(C₅H₅N)₂·(C₆H₈N)₂·1.5CH₃OH (2) have been successfully synthesized under hydrothermal conditions. Structural analysis indicates that the polyoxoanion of compound 1 is a solvent molecule-bonded zinc-monosubstituted Keggin structural cluster, [PMo₁₁O₃₉Zn(C₅H₅N)]⁵⁻, while the polyoxoanion of compound 2 is a cobalt-monosubstituted phosphotungstate polyanion bonded with one pendant pyridine molecule. Both 1 and 2 show 3D supramolecular interpenetrating structures constructed of inorganic polyanion layers and organic layers. Very interestingly, compounds 1 and 2 exhibit excellent third-order NLO properties, and the TPA cross section σ of 1 and 2 is 2571.3 GM and 2876.3 GM, respectively.