Hydrothermal Syntheses, Structural Characterizations, and Photoluminescence Properties of Three Fluorinated Indium Phosphates with Bipyridyl Ligands: In3F2(2,2‘-bipy)2(HPO4)2(H1.5PO4)2, In2F2(H2O)(2,2‘-bipy)(HPO4)2, and In2F2(H2O)(2,2‘-bipy-5-amine)(HPO4)2

Abstract

Three novel fluorinated indium phosphates with the formulas In3F2(2,2‘-bipy)2(HPO4)2(H1.5PO4)2 (1), In2F2(H2O)(2,2‘-bipy)(HPO4)2 (2), and In2F2(H2O)(2,2‘-bipy-5-amine)(HPO4)2 (3) have been prepared hydrothermally in the presence of 2,2‘-bipy and 2,2‘-bipy-5-amine ligands. Single-crystal X-ray diffraction analysis reveals that 1 possesses an unusual neutral chained structure, which is not only the first 1D chain in the indiumphosphate family but also shows a new type of chain structure compared with those metalphosphates reported in the literature. Meanwhile, 2 and 3 present 2D undulated sheetlike structures with the same inorganic framework topology. The adjacent layers are stably packed together and exhibit interesting 3D supramolecular arrays with π−π interactions of the bipy groups. It is noteworthy that the different ratios of In:P for reactant addition lead to the formation of different structures in the presence of the same bipy ligands (In:P = 1:6 for compound 1 and In:P =1:4 for 2). By comparatively studying the photoluminescence properties of these compounds, we may conclude that the photoluminescence originates from ligand-centered π−π* transitions. The as-synthesized products are further characterized by powder X-ray diffraction, thermogravimetric analysis, 31P MAS NMR and IR spectroscopy, ICP, and elemental analysis.