Four metal–organic architectures from a triphenyl-tricarboxylic acid: synthesis, crystal structures, and catalytic features

Semi-flexible aromatic polycarboxylic acids are gaining impetus in crystal engineering of functional coordination polymers. This work opens up the use of a triphenyl-tricarboxylic acid, 3,5-(4'-carboxylphenyl) benozoic acid (H₃cba), as a versatile and still unexplored linker for the synthesis of four new Mn(II), Ni(II), Zn(II), and Cd(II) coordination polymers, formulated as [Mn(μ₃-Hcba)(bpy)]_n⋅nH₂O (1), [Ni(μ-Hcba)(py)(H₂O)]_n (2), [Zn(μ-Hcba)(phen)(H₂O)]_n⋅nH₂O (3), and [Cd(μ₃-Hcba)(bpy)]_n⋅nH₂O (4). These compounds were prepared via a facile hydrothermal procedure using metal(II) chlorides, H₃cba, and supporting N-donor ligands (2,2΄-pyridine, bpy; pyridine, py; 1,10-phenanthroline, phen) acting as crystallization mediators. Compounds 1–4 were fully characterized and their X-ray crystal structures were established, disclosing the metal–organic architectures that range from 1D double chains (1, 4) to 1D chains (2, 3). Thermal and catalytic properties of 1–4 were also investigated. In particular, catalytic potential of the obtained coordination polymers in the Knoevenagel condensation of benzaldehydes with propanedinitrile was evaluated, disclosing an excellent performance of several heterogeneous catalysts with up to 100% product yield.

Graphical abstract

Four new Mn(II), Ni(II), Zn(II), and Cd(II) 1D coordination polymers have been constructed and the structures and catalytic properties of the polymers were investigated.