Metal-Organic Architectures Assembled from Multifunctional Polycarboxylates: Hydrothermal Self-Assembly, Structures,...

A three-component aqueous reaction system comprising copper(II) acetate (metal node), poly(carboxylic acid) with a phenylpyridine or biphenyl core (main building block), and 1,10-phenanthroline (crystallization mediator) was investigated under hydrothermal conditions. As a result, four new coordination compounds were self-assembled, namely, {[Cu(μ₃-cpna)(phen)]·H₂O} _n (1), {[Cu(μ-Hbtc)(phen)]·H₂O} _n (2), {[Cu(μ₃-Hcpic)(phen)]·2H₂O} _n (3), and [Cu₆(μ-Hcptc)₆(phen)₆]·6H₂O (4), where H₂cpna = 5-(2'-carboxylphenyl)nicotinic acid, H₃btc = biphenyl-2,4,4'-tricarboxylic acid, H₃cpic = 4-(5-carboxypyridin-2-yl)isophthalic acid, H₃cptc = 2-(4-carboxypyridin-3-yl)terephthalic acid, and phen = 1,10-phenanthroline. Crystal structures of compounds 1-3 reveal that they are 1D coordination polymers with a ladder, linear, or double-chain structure, while product 4 is a 0D hexanuclear complex. All of the structures are extended further [1D → 2D (1 and 2), 1D → 3D (3), and 0D → 3D (4)] into hydrogen-bonded networks. The type of a multicarboxylate building block has a considerable effect on the final structures of 1-4. The magnetic behavior and thermal stability of 1-4 were also investigated. Besides, these copper(II) derivatives efficiently catalyze the oxidation of cycloalkanes with hydrogen peroxide under mild conditions. The obtained products are the unique examples of copper derivatives that were assembled from H₂cpna, H₃btc, H₃cpic, and H₃cptc, thus opening up their use as multicarboxylate ligands toward the design of copper-organic architectures.