A 12-molybdophosphoric acid supramolecular compound: Synthesis, crystal structure and photochromic properties

A new 12-molybdophosphoric acid supramolecular compound based on Keggin polyoxometalate building blocks, (C6H6NO2)·(C5H6N)2·[PMo12O40]·(C6H5NO2)·2H2O (1), has been conventionally synthesized and structurally characterized by elemental analyses, the powder X-ray diffraction (XRD), TG, IR, and single crystal X-ray diffraction, respectively. Compound 1 is composed of polyoxometalate anions [PMo12O40]3−, pyridinium cations, 4-carboxylpyridinium cation and lattice water. A three-dimensional network is formed by N–H⋯O, C–H⋯O and O–H⋯O hydrogen-bond interactions. In addition, the supramolecular compound shows photochromism.