Controllable assembly of multicarboxylic acids functionalized heteropolyoxomolybdates and allochroic properties

Abstract

A series of inorganic–organic hybrid heteropolyoxomolybdates built from [TeMo₆O₂₁]²⁻ polyoxoanions and multicarboxylic acids including (C₃N₂H₅)₄H₆[(TeMo₆O₂₁)₂{O₂C(CH₂)₂CO₂}₃]·9.5H₂O (1), (C₃N₂H₅)₈H₂[(TeMo₆O₂₁)₂{O₂C(CH₂)₆CO₂}₃]·3.5H₂O (2) and (CN₃H₄)₁₆H₄[(TeMo₆O₂₁)₄{C₆H₃(COO)₃}₄]·16H₂O (3) have been synthesized arising from the reactions of (NH₄)₆Mo₇O₂₄·4H₂O, Na₂TeO₃/TeO₂ and the corresponding multicarboxylic acids in an aqueous medium. X-ray single crystal diffraction, X-ray powder diffraction (XPRD), elemental analyses, inductively coupled plasma (ICP) spectra, IR spectra, UV spectra and thermogravimetric (TG) analyses have been implemented. Crystal structure analyses reveal that both compounds 1 and 2 are dimers, while 3 is a tetramer, however, they contain the same {TeMo₆} unit which consists of a six-membered MoO₆ octahedral ring capped by one {TeO₃} trigonal pyramid. Compounds 1–3 exhibit intriguing allochroic properties. They can change color from white to blue/green when heated. Upon the irradiation of a xenon lamp (full wave-band, P = 300 W), their color can change from white to reddish brown.