Two Unprecedented POM-Based Inorganic-Organic Hybrids with Concomitant Heteropolytungstate and Molybdate

Abstract

Two novel POM-based inorganic-organic hybrids, [Cu₆^II(2,2'-bipy)₆(Mo₆O₂₂)(SiW₁₂O₄₀)]_n (1), and {[Cu₆^II(ppz)₆(H₂O)₅(MoO₄)(SiW₁₂O₄₀)]·4H₂O}_n (2) (2,2'-bipy = 2,2'-bipyridine, Hppz = 3-(pyrid-2-yl)pyrazole), have been constructed from heteropolytungstates and molybdates. Two compounds have been identified by single crystal X-ray diffraction, elemental analysis, and FT-IR. Compound 1 shows a 1D (one-dimensional) chain structure constructed from classical Keggin heteropolytungstate [SiW₁₂O₄₀]^4- clusters and [Cu₆(2,2'-bipy)₆] modified isopolymolybdates [Mo₆O₂₂]^8-. Compound 2 also represents a 1D chain-like motif built from classical Keggin heteropolytungstate [SiW₁₂O₄₀]^4- clusters and [Cu₈(ppz)₆(H₂O)₅] modified molybdates MoO₄^2-. Compound 1 represents the first example of POM-based inorganic-organic hybrid with mixed heteropolytungstates and isopolymolybdates. ESI-MS (electrospray ionization mass spectrometry) technique was employed to reveal the species and their evolutions in the hydrothermal reaction, whereby trivacant [SiW₉] building block gradually transforms to classical Keggin [SiW₁₂] during assembly process. Furthermore, the electrocatalytic and magnetic properties were discussed in details.