Influence of Ligand Geometry on the Formation of In−O Chains in Metal-Oxide Organic Frameworks (MOOFs)

Three indium-oxide organic frameworks, In2O(1,3-BDC)2, 1; In(OH)(2,6-NDC)(H2O), 2; and In(OH)(2,7-NDC)(H2O),
3 (BDC = benzene dicarboxylic acid and NDC = naphthalene dicarboxylic acid), were synthesized and characterized
by thermogravimetric analysis, infrared spectroscopy, and single-crystal X-ray diffraction. Previously, we reported
the structure of In(OH)(1,4-BDC)·(0.75H2BDC), 0, where the framework is built by interconnecting In−OH−In chains
with the BDC anions to form large diamond-shaped one-dimensional channels filled with guest molecules. Compounds
0−3 all contain In−O(H) chains, but the coordination and geometry depend on the nature of the dicarboxylate
ligand. Compound 0 contains In−O octahedral centers that connect to form a single trans octahedral chain, while
in compound 1, they connect to form a more complex double chain of octahedra. Both compounds 2 and 3 contain
chains of connected pentagonal bipyramidal InO6(OH2) units. In 2, these units share trans vertices that are cross-linked by chelating 2,6-NDC anions, whereas in compound 3, cis vertices are shared to form chains that are linked
by the 2,7-NDC anions.