Crystal structure and solid-state nuclear magnetic resonance characterization of an oxyfluorinated three-dimensional framework gallophosphate with ULM-4 structural type. Structural relationships with GaAsO 4-2

Abstract

Ga 3(PO 4) 3F 2, 0.75 H 3N(CH 2) 3NH 3, 0.5 H 3O (ULM-4) was obtained by hydrothermal synthesis (453 K, 24 h, autogenous pressure) from a mixture of Ga 2O 3, H 3PO 4, HF, 1,3-diaminopropane and H 2O in the ratio 1:2:2:1.3:80. The structure was studied by single-crystal X-ray diffraction and solid state NMR. It is monoclinic (space group P2 1/ n (no. 14)) with a = 8.674(1)Å, b = 10.190(2) Å, c = 16.826(3) Å, β = 94.21(2)°, V= 1483.1(7) Å 3 and Z=4. The open framework delimits one-dimensional 10-ring channels; it is built up from the hexameric unit Ga 3(PO 4) 3F 2 in which the gallium atoms exhibit two types of surrounding. One of the three gallium atoms is octahedrally coordinated and the two others are in trigonal bipyramidal coordinations where fluorine atoms link the gallium atoms together. Strong hydrogen bonding interactions between the fluorine and the amine functions of the diamines are evidenced. The structure was examined by 31P, 19F, 15N and 13C solid-state nuclear magnetic resonance spectroscopy. Structural relationships with GaAsO 4-2 are discussed.