Terphenyl-Tricarboxylate Coordination Polymers: From Hydrothermal Assembly to Structural Diversity and Catalytic Application

An aromatic tricarboxylic acid building block, [1,1′:3′,1″-terphenyl]-4,4″,5′-tricarboxylic acid (H₃tptca), was used as a versatile linker for assembling, under hydrothermal conditions, a series of 12 new coordination polymers (CPs) in the presence of supporting N-donor ligands acting as mediators of crystallization. The obtained products were formulated as [Mn(μ-Htptca)(phen)₂]_n·nH₂O (1), [Zn(μ-Htptca)(2,2′-bipy)(H₂O)]_n·nH₂O (2), [Ni(μ₃-Htptca)(μ-4,4′-bipy)]_n·2nH₂O (3), [Co(μ₃-Htptca)(μ-bpe)]_n (4), [M₃(μ₃-tptca)₂(phen)₃(H₂O)₂]_n·2nH₂O (M = Co (5), Zn (6)), [Co₂(μ₄-tptca)(μ-OH)(2,2′-bipy)₂]_n (7), [Zn₃(μ₃-tptca)₂(2,2′-bipy)₃(H₂O)₂]_n·4nH₂O (8), {[Cd(H₂biim)₃][Cd₂(μ₃-tptca)(μ₅-tptca)]}_n (9), [Co₂(μ₄-tptca)(μ-bpa)(μ₃-OH)(H₂O)₂]_n·nH₂O (10), [Ni₃(μ₃-tptca)₂(μ-bpa)₃(H₂O)₄]_n·5nH₂O (11), and [Co₂(μ₄-tptca)(μ-bpb)(μ-OH)]_n (12), wherein phen, 2,2′-bipy, 4,4′-bipy, bpe, H₂biim, bpa, and bpb are 1,10-phenanthroline, 2,2′- and 4,4′-bipyridine, 1,2-di(4-pyridyl)ethane, 2,2′-biimidazole, bis(4-pyridyl)amine, and 1,4-bis(pyrid-4-yl)benzene, respectively. Crystal structures of CPs 1–12 reveal a broad diversity metal–organic networks that range from 1D chains (1, 2, 5, 6, and 8) to 2D layers (3, 4, 7, 9, and 11) and 3D nets (10 and 12), including the examples of interpenetrated, polycatenated, and topologically unique architectures. Structural features and catalytic properties of the obtained CPs were studied and discussed. In particular, a Zn(II) CP 8 acts as an efficient and recyclable heterogeneous catalyst for the mild cyanosilylation of benzaldehydes, leading to the formation of the corresponding cyanohydrin products in up to 99% yields. The obtained compounds widen a growing family of functional CPs driven by terphenyl-tricarboxylate linkers.