Hydrothermal synthesis and ab initio structural approach of two new layered oxyfluorinated titanium(IV) phosphates: Ti-2(PO4)(2)F-4 center dot N2C2H10(MIL-6) and Ti-2(PO4)(2)F-4 center dot N2C3H12 center dot H2O

Ti-2(PO4)(2)F-4. N2C2H10 (MIL-6) and Ti-2(PO4)(2)F-4. N2C3H12H2O were prepa red hydrothermally (3 days, 453-483 K, autogenous pressure) in the presence of an organic template (ethylenediamine or 1,3-diaminopropane). The struct ures of Ti-2(PO4)(2)F-4. N2C2H10 1 and Ti-2(PO4)(2)F-4. N2C3H12. H2O 2 were determined ab initio from powder diffraction data. These structures exhibi t different monoclinic distortions of the VOPO4. 2H(2)O structure type. 1: space group P2(1)/c (no. 14), a = 7.508(1), b = 8.881(1), c = 8.961(1) Angs trom, beta = 107.22(1)degrees and V = 570.8(1) Angstrom(3). 2: space group C2 (no. 5), a = 16.820(2), b = 6.333(2), c = 6.331(2) Angstrom, beta = 106. 20 degrees and V = 645.8(1) Angstrom(3). Both are layered compounds built u p from TiO4F2 octahedra linked together by PO4 tetrahedra; the Ti-F bonds a re oriented perpendicularly to the layers which contain the diprotonated am ine. The stability of the structures is ensured by the strong hydrogen bond ing between the fluorine atoms and the amino groups.