Octahedral Tilting in MM′X₄ Metal-Oxide Organic Layer Structures

Three metal-oxide organic frameworks have been synthesized and characterized: vanadium 1,4-benzenedicarboxylate, V₂O₂F_0.6(OH)_1.4(BDC)·0.4H₂O (1); indium 1,4-benzenedicarboxylate, In₂F_2.2(OH)_1.8(BDC)·1.6H₂O (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^III₂(OH)₂F₂(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′X₄. 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) Å, b = 3.8416(11) Å, c = 20.570(6) Å; 2, orthorhombic, space group Cmcm, a = 7.490(4) Å, b = 21.803(1) Å, c = 8.154(4) Å; 3, monoclinic, space group P2₁/m, a = 10.7569(8) Å, b = 6.7615(3) Å, c = 7.1291(3) Å, β = 76.02(1)°.