Series of Metal–Organic Frameworks Including Novel Architectural Features Based on a Star-like Tri(4-pyridylphenyl)amine Ligand

Six new metal–organic frameworks with novel structural features based on a star-like ligand tri­(4-pyridylphenyl)­amine (TPPA), namely, {[Cd­(TPPA)­(pht)­(H2O)]­(H2O)2}n (1), {[Zn­(TPPA)­(pht)]­(H2O)2}n (2), {[Zn­(TPPA)­(trans-chdc)0.5(NO3)]·(H2O)}n (3), {[Co­(TPPA)­(bdc)­(H2O)]·(H2O)}n (4), {[Co­(TPPA)­(bdc)­(H2O)]·(H2O)4}n (5), and {[Co­(TPPA)­(bdc)]}n (6) (H2pht = phthalic acid, trans-H2chdc = trans-1,4-cyclohexanedicarboxylic acid, H2bdc = benzene-p-dicarboxylic acid), have been synthesized under solvothermal conditions. Compounds 1–3 all exhibit fascinating 2D → 3D frameworks with coexistence of inclined polycatenation and polythreading characters. On the other hand, compounds 4–6 are three supramolecular isomers. Even though the compositions of 4–6 are almost same, they generate different structures. Compound 4 shows a 2D → 3D framework with parallel polycatenation of undulated square layers. Compound 5 reveals 3-fold interpenetrating 3D frameworks with {4.62}­{43.67} crs topology. Compound 6 shows a 4-fold interpenetrating 3D metal–organic polyrotaxane framework. In addition, photophysical properties of 1–3 and the TPPA ligand in the solid state have also been studied.