Diverse Structures of Metal-Organic Frameworks Based on a New Star-Like Tri(4-pyridylphenyl)amine Ligand

Four new metal-organic frameworks based on a new star-like ligand tri(4-pyridylphenyl)amine (TPPA), namely, {[Cd(TPPA)(trans-chdc)]}(n) (1), {[Co(TPPA)2(D-ca)(2)]center dot(H2O)}(n) (2), {[Ni(TPPA)(bdc)(H2O)]-(H2O)(4)}(n) (3), {[Ni(TPPA)(trans-chdc)-(H2O)center dot(H2O)(4)}(n) (4), (trans-H(2)chdc = trans-1,4-cyclohexanedicarboxylic acid, D-H(2)ca. = D-camphor acid, acid, H(2)bdc = benzene-p-dicarboxylic acid), have been synthesized under solvothermal conditions. Compound 1 represents the first example of a 4-fold interpenetrating 3D metal-organic polyrotaxane framework, with {4(2).6(5).8(3)}{4(2).6} AFUQOH topology. In 2, each D-ca(2-) anion links adjacent Co2+ atoms to a 2D framework, and only one N atom from each TPPA ligand is involved in coordination, which should be partly attributed to the weak flexibility of the TPPA ligand. Both 3 and 4 reveal 3-fold interpenetrating 3D frameworks bridged by TPPA ligands and bdc(2-) (or trans-chdc(2-)) anions, with {4.6(2)}{4(3).6(7)} crs topology. In addition, photophysical properties of 1 and the TPPA ligand in the solid state have also been studied.