Coordination Polymers from an Amino-Functionalized Terphenyl-Tetracarboxylate Linker: Structural Multiplicity and Catalytic Properties

An amino-functionalized terphenyl-tetracarboxylic acid, 2 '-amino-[1,1 ':4 ',1 ''-terphenyl]-3,3 '',5,5 ''-tetracarboxylic acid (H(4)tpta), was used as an adaptable linker to synthesize, under hydrothermal conditions, eight coordination polymers (CPs). The obtained products were formulated as [Co(mu(6)-H(2)tpta)](n) (1), [Co(mu(3)-H(2)tpta)(2,2 '-bipy)](n) (2), [M-3(mu(6)-Htpta)(2)(2,2 '-bipy)(2)](n) (M = Mn (3), Cd (4)), [Ni-2(mu(4)-tpta)(phen)(2)(H2O)(4)](n) (5), [Zn-2(mu(6)-tpta)(phen)(2)](n) (6), {[Zn-2(mu(6)-tpta)(mu-4,4 '-bipy)]H2O}(n) (7), and [Zn-2(mu(6)-tpta)(mu-H(2)biim)(H2O)(2)](n) (8), wherein 2,2 '-bipyridine (2,2 '-bipy), 4,4 '-bipyridine (4,4 '-bipy), 1,10-phenanthroline (phen), or 2,2 '-biimidazole (H(2)biim) are present as additional stabilizing ligands. The structural types of 1-8 vary from one-dimensional (1D) (2, 5) and two-dimensional (2D) (3, 4, 6) CPs to three-dimensional (3D) metal-organic frameworks (MOFs) (1, 7, and 8) with a diversity of topologies. The products 1-8 were investigated as catalysts in the Knoevenagel condensation involving aldehydes and active methylene derivatives (malononitrile, ethyl cyanoacetate, or tert-butyl cyanoacetate), leading to high condensation product yields (up to 99%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were investigated. This work broadens the application of H(4)tpta as a versatile tetracarboxylate linker for the generation of diverse CPs/MOFs.