Synthesis, characterization and structure determination of a new fluorogallophosphate (Mu-3) prepared in the presence of ethylene glycol as main solvent

A new fluorinated gallium phosphate was synthesized from a quasi-non-aqueous medium using ethylene glycol as solvent and the bulky amine 4-amino-2,2,6,6-tetramethylpiperidine as organic template. This material was characterized by elemental analysis, X-ray diffraction and solid state NMR spectroscopy. The crystal structure was determined by single crystal X-ray diffraction. The symmetry is trigonal, space group P3 [a=20.0476(2) Angstrom, c=8.5839(1) Angstrom]. The structure consists of anionic fluorinated gallophosphate chains of D4R units hosting F-. The location of the fluorine atoms was confirmed by F-19 solid-state NMR spectroscopy. Two signals corresponding to F- trapped in D4R units (delta = -73 ppm/CFCl3) and to terminal fluorine (delta = -166 ppm/CFCl3) are observed. The negative charge of the inorganic chains is compensated by the doubly protonated amine. This new gallophosphate shows low thermal stability, a complete amorphization being observed after calcination at 300 degrees C. (C) 1998 Elsevier Science B.V. All rights reserved.