pH-Dependent Assembly of Three POM-Based Host-Guest Compounds Constituted by Keggin Polyoxoanions and 4,4′-Bipyridines.

Three POM-based host-guest compounds constituted by Keggin-type polyoxometalates (POMs): (4,4′-Hbpy)3 [PMo12O40]·2H2O (1); (4,4′-H2bpy)3[PMo12O40]2·3H2O (2) and (4,4′-H2bpy) (4,4′-Hbpy)·[PW12O40]·4H2O (3) (bpy = 4,4′-bpyridine) have been synthesized hydrothermally and characterized by elemental analyses, IR, XPS spectra, powder XRD analyses, cyclic voltammetric measurements and single-crystal X-ray diffraction analyses. The three compounds all consist of Keggin-type POMs and 4,4′-bpy ligand, which are [PMo12O40]3− for 1-2 and [PW12O40]3− for 3. Through O···O interactions, Keggin POMs each other give rise to three different 3-D Supermolecular host structures, 4,4′-bpy and water molecules as guests accommodate different channels with H-bonding interactions. Discuss the pH role for the build POM based-hybrids contained 4,4′-bpy ligand. The photocatalytic properties of 1-3 have been investigated in the solid state. [ABSTRACT FROM AUTHOR]