Crystal engineering with 1-benzofuran-2,3-dicarboxylic acid: Co-crystals with bipyridyl ligands, discrete complexes and coordination polymers with metal ions

This study evaluates the versatile supramolecular reactivity of the title dicarboxylic ligand (BFDC), via hydrogen bonding towards complementary organic ligands, and via metal-ligand coordination with various metal ions. Fourteen new crystalline compounds have been obtained and their structures characterized by single-crystal X-ray diffraction. BFDC was found to form trimeric 2:1 hydrogen-bonded assemblies with bipyridyl moieties, associated with the transfer of two protons from the diacid to the bipyridyl. Reactions of the BFDC with d- and f-transition metal ions yielded either 2:2 (dimeric) or 4:2 (tetrameric) discrete dinuclear metal-ligand complexes, as well as one-dimensional coordination polymers in which the diacid entities act as multidentate bridging ligands between adjacent metal ions along the polymeric backbone. The large diversity of the obtained products suggests that in the experimental conditions used, it seems practically impossible to predict the outcome of a given reaction. All the compounds were crystallized from aqueous environments and exhibit extended arrays of intermolecular hydrogen bonding.