Two-Dimensional Bicapped Supramolecular Hybrid Semiconductor Material Constructed from the Insulators alpha-Keggin Polyoxomolybdate and 4,4 '-Bipyridine

Abstract

A new organic inorganic hybrid material [SiMo14O44](H4,4'-bpy)(2)center dot xH(2)O (4,4'-bpy = 4,4'-bipyridine) was synthesized using a hydrothermal method. The compound was characterized using single crystal X-ray diffraction (XRD), infrared spectroscopy (IR), ultraviolet visible spectroscopy (UV-vis), and X-ray photoelectron spectroscopy (XPS). XRD studies on selected single crystals suggested that the compound consists of supramolecular 2D layer structures composed of capped alpha-Keggin polyoxomolybdate anions and 4,4'-bpy organic ligands. Absorption measurements show a band gap of 2.99 eV in the hybrid which suggests a semiconducting nature compared to the insulating free alpha-Keggin and 4,4'-bpy. The magnetic susceptibility of the hybrid material was investigated in the temperature range 1.8-300 K obeying the Curie-Weiss law above 70 K. Experimentally measured magnetic moment of 2.71 mu(B)/formula indicates possible mixed valent molybdenum in the compound. The XPS measurements confirm the presence of both Mo-V and Mo-VI in the ratio 15:85 resulting in the structural formula of the hybrid as [(SiMo2Mo12O44)-Mo-V-O-VI](H4,4'-bpy)(2)center dot xH(2)O.