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]·(H2O)}n (2), {[Ni­(TPPA)­(bdc)­(H2O)]·(H2O)4}n (3), {[Ni­(TPPA)­(trans-chdc)­(H2O)]·(H2O)4}n (4), (trans-H2chdc = trans-1,4-cyclohexanedicarboxylic acid, d-H2ca. = d-camphor acid, H2bdc = 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 {42.65.83}­{42.6} AFUQOH topology. In 2, each d-ca2– 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 bdc2– (or trans-chdc2–) anions, with {4.62}­{43.67} crs topology. In addition, photophysical properties of 1 and the TPPA ligand in the solid state have also been studied.