Hydrothermal synthesis and characterization of the first 1-D indiumphosphate chain In2(HPO4)2(H2PO4)2F2·C4N2H12, a precursor for high dimensional structures

The first one-dimensional (1-D) indiumphosphate chain, In2(HPO4)2(H2PO4)2F2·C4N2H12 (1), has been hydrothermally prepared using piperazine (PIP) as a template. The structure consists of infinite chains of trans,trans-corners-sharing InO4F2 octahedra with the adjacent octahedra being bridged by tetrahedral PO3(OH) and PO2(OH)2 units, which are H-bonded with amine groups of the organic cations. Interestingly, this macroanionic chain InP2O8H3F− is similar to that found in the mineral tancoite-like chains and has potential to further set up higher-dimensional networks. On heating 1 in the presence of additional phosphoric acid at 180 °C under hydrothermal condition, compound 2, In2(OH)(H2O)(PO4)2·H3O·H2O, possessed a 3-D structure building from the repetition of a secondary building unit is obtained. When 1 is heated with additional PIP, an unknown phase, compound 3 is formed. Finally, on treatment with another amine, such as diethylenetriamine or 1,4-diaminobutane, at 180 °C, 1, as a precursor, can convert into a previously known 3-D framework structure with 16-membered ring compound 4. Compounds 1 and 2 are determined by single-crystal X-ray diffraction. Furthermore, 1 is characterized by X-ray powder diffraction, IR spectroscopy, inductively coupled plasma analysis, thermogravimetric analysis and differential thermal analysis.