The crystal structure and characterization of 2-D and 3-D indium phosphates synthesized from a water/ethylene glycol mixed-solvent system

Abstract

Three indium phosphates [In16(HPO4)28(H2O)12](NH4)8(H2O)12 (1), [In2(OH)(HPO4)2(PO4)](H2O)(C6H18N2) (2) and [In3(HPO4)6](C2N2H10)(H3O)(H2O)2 (3) were solvothermally synthesized from water/ethylene glycol (EG) mixed solvent systems by using 1,3-propyldiamine (1,3-PDA), 2-methyl-pentamethylenediamine (MPMD) and diethylenetriamine (DETA) as structure directing agents (SDAs), respectively. Compound 1 consists of anionic layers of [In7(HPO4)14(H2O)6]7−, which are connected by InO6 octahedra to form an anionic three-dimensional (3-D) open framework with intersecting 12-membered rings channels. The channels are filled with charge-balancing ammonium cations and guest water molecules. Compound 2 possesses a 2-D layered structure consisting of anionic layers of [In2(OH)(HPO4)2(PO4)]2– formed by InO6 octahedra and PO4 tetrahedra, in which the protonated MPMD and water molecules lie between the layers. Compound 3 is constructed from a [3.3.3] propellane-like building unit made of strict alternation of InO6 octahedra and PO4H tetradedra, forming a 3-D open framework with intersecting 8- and 12-membered ring channels. The protonated water and ethylenediamine derived from the decomposition of DETA during the synthesis are located within the channels. The three compounds were characterized by powder X-ray diffraction (PXRD), single crystal X-ray diffraction, Fourier-transformed infrared (FT-IR) spectra, thermogravimetric analysis (TGA), inductively coupled plasma-atomic emission spectroscope (ICP-AES) and elemental analyses.