A three-dimensional coordination polymer of 3-(3,5-dicarboxybenzyloxy)benzoic acid with zinc.

The synthesis is reported of the tricarboxylic acid 3-(3,5-dicarboxybenzyloxy)benzoic acid (H₃L) and the product of its reaction under solvothermal conditions with ZnII cations, namely poly[μ₆-3-(3,5-dicarboxylatobenzyloxy)benzoato-μ₃-hydroxido-dizinc(II)], [Zn₂(C₁₆H₉O7)(OH)(C₃H₇NO)]n, the formation of which is associated with complete deprotonation of H₃L. Its crystal structure consists of a single-framework coordination polymer of the organic L³⁻ ligand with ZnII cations in a 1:2 ratio, with additional hydroxide and dimethylformamide (DMF) ligands coordinated to the ZnII centres. The ZnII cations are characterized by coordination numbers of 5 and 6, being bridged to each other by hydroxide ligands. In the polymeric framework, the carboxylate- and hydroxy-bridged ZnII cations are arranged in coordination-tessellated columns, which propagate along the a axis of the crystal structure, and each L³⁻ ligand links to seven different ZnII centres via Zn-O bonds of two different columns. The coordination framework, composed of [Zn₂(L)(OH)(DMF)]n units, forms an open architecture, the channel voids within it being filled by the zinc-coordinating DMF ligands. This report provides the first structural evidence for the formation of coordination polymers with H₃L via multiple metal-ligand bonds through its carboxylate groups.