Metal-organic architectures designed from a triphenyl-pentacarboxylate linker: hydrothermal assembly, structural multiplicity, and catalytic Knoevenagel condensation

A triphenyl-pentacarboxylic acid, 3,5-di(2′,4′-dicarboxylphenyl)benzoic acid (H 5 ddba), was applied as an adaptable linker for the hydrothermal assembly of eight new metal( ii ) coordination polymers (CPs) and complexes, formulated as [Cu 2 (μ-H 3 ddba) 2 (phen) 2 ] ( 1 ), {[Cd 2 (μ 4 -Hddba)(phen) 2 (H 2 O) 2 ]·2H 2 O} n ( 2 ), [M 4 (μ 3 -Hddba) 2 (2,2′-bipy) 6 (μ-H 2 O)]·6H 2 O (M = Ni ( 3 ), Mn ( 4 )), {[Co 2 (μ 5 -Hddba)(μ-4,4′-bipy) 1.5 (H 2 O)]·H 2 O} n ( 5 ), {[Zn 2 (μ 5 -Hddba)(4,4′-bipy) 1.5 ]·4,4′-bipy·2H 2 O} n ( 6 ), [Mn 2 (μ 6 -Hddba)(H 2 biim)(H 2 O)] n ( 7 ), and {[Cd 2 (μ 7 -ddba)(Hbpa)]·5H 2 O} n ( 8 ). The products 1-8 were generated from metal( ii ) chlorides, H 5 ddba, and various N-donor supporting ligands acting as mediators of crystallization ( i.e. , phen: 1,10-phenanthroline; 2,2′-bipy: 2,2′-bipyridine; 4,4′-bipy: 4,4′-bipyridine; H 2 biim: 2,2′-biimidazole; or bpa: bis(4-pyridyl)amine). All compounds were analyzed by standard methods (C/H/N analysis, FTIR, TGA and PXRD) including single-crystal X-ray diffraction. The structural multiplicity of 1-8 ranges from discrete dimers ( 1 ) or tetramers ( 3 and 4 ) to a 1D coordination polymer ( 2 ) and 3D metal-organic frameworks ( 5-8 ). Topological analysis of simplified H-bonded or metal-organic networks disclosed fcu ( 1 ), 2C1 ( 2 ), dia ( 3 and 4 ), sra ( 6 ), 3,4,7T3 ( 8 ), and unprecedented ( 5 and 7 ) topologies. The catalytic activity of 1-8 was investigated in a model Knoevenagel condensation between benzaldehydes and malononitrile, resulting in up to 99% yields of condensation products. The substrate scope, catalyst recycling, and effects of different reaction parameters were investigated. Finally, this work extends the use of H 5 ddba as an aromatic pentacarboxylate building block for the design of new metal-organic architectures with captivating structures and functional properties. Eight new metal( ii ) coordination compounds driven by a triphenyl-pentacarboxylate linker were hydrothermally assembled and fully characterized. Their structural features and catalytic behavior were investigated.