A helical chain-like organic–inorganic hybrid arsenotungstate with color-tunable photoluminescence

Abstract

A 1-D infinite helical chain-like organic–inorganic hybrid arsenotungstate Na₄H₈[{Pr(H₂O)₂}₂{As₂W₁₉O₆₈}{WO₂(mal)}₂]·24H₂O (mal = malate) (1) was prepared, which was characterized by elemental analyses, thermogravimetric (TG) analyses, IR spectroscopy, powder X-ray diffraction (PXRD) and X-ray single-crystal diffraction. Structural characterization revealed that 1 comprises the organo-functionalized [{As₂W₁₉O₆₈}{WO₂(mal)}₂]¹⁸⁻ polyanions hinged together by the Pr³⁺ ions forming a 1-D infinite helical chain-like architecture. The malate ligand may play a vital role to stabilize the structure of 1 by the formation of the five-membered W–O–C–C–O chelate ring. Solid state photoluminescence reveals that 1 features excitation wavelength-dependent emission properties, achieving a reversible emission color switching simply via changing the excitation wavelength. Time-resolved emission spectroscopy (TRES) indicates that the photoexcitation O → M ligand to metal charge transfer (LMCT) of arsenotungstate fragments can sensitize the Pr³⁺ ions through intramolecular energy transitions in 1.