Octahedral tilting in MM'X4 metal-oxide organic layer structures

Three metal-oxide organic frameworks have been synthesized and characterized: vanadium 1,4-benzenedicarboxylate, V2O2F0.6(OH)(1.4)(BDC)center dot 0.4H(2)O (1); indium 1,4-benzenedicarboxylate, In2F2.2(OH)(1.8)(BDC)center dot 1.6H(2)O (2); and aluminum 1,4-benzenedicarboxylate Al2F3(OH)(BDC) (3). The three-dimensional structures of 1, 2, and 3 have the same framework topology as the previously reported vanadium (III) 1,4-benzenedicarboxylate, V-2(III)(OH)(2)F-2(BDC). The frameworks consist of inorganic layers constructed from corner sharing ML6 octahedra (M = V, In, Al and L = OH, F) linked by BDC ligands. The structures are related to a general class of perovskite-related layer structures with composition MM'X-4. The layers show characteristic distortions that can be related to tilting of the ML6 octahedra. In particular the structure of 1 consists of O-V distances that strongly alternate along the b axis. The electronic consequences of this distortion then create a tilting of the 1,4-benzenedicarboxylate ligand about the a axis. Crystal data: 1, orthorhombic, space group Pmna, a = 7.101(2) angstrom, b = 3.8416(11) angstrom, c = 20.570(6) angstrom; 2, orthorhombic, space group Cmcm, a = 7.490(4) angstrom, b = 21.803(1) angstrom, c = 8.154(4) angstrom;. 3, monoclinic, space group. P2(1)/m, a = 10.7569(8) angstrom, b = 6.7615(3) angstrom, c = 7.1291(3) angstrom, beta = 76.02(1)degrees.