Coordination polymers incorporating Bi(III) and 2,4,6-pyridine tricarboxylic acid and its derivatives: Synthesis, structure and topology

Abstract

Bi(III) as its oxide combined with 2,4,6-pyridine tricarboxylic acid, H2pdc-COOH, and various pyridine-derived additives in dimethylformamide (dmf) under solvothermal conditions produced three novel bismuth coordination polymers, {[Bi(μ-pdc-COO)2][NH2Me2]3}n, 1, {[Bi(μ-pdc-COO)2][C5H7N2]3·C5H6N2}n, 2, and {[Bi2(μ-pdc-COO)2(μ-pdc-COOH)(pdc-COOH)][NH2Me2]4·2dmf·NHMe2}n, 3. The anionic coordination network topologies are two-dimensional, chains-of-loops and ladders, respectively, but the local 8-coordinate environments about the bismuth(III) centres are in each case between that of a square antiprism and that of a hexagonal bipyramid. When the 4-carboxy substituent in H2pdc-COOH is replaced by another potentially coordinating substituent to give 4-R-2,6-pyridine dicarboxylic acid, H2pdc-R (R = OH, NH2, Cl), the salts obtained contain discrete centrosymmetric dinuclear 8-coordinate bismuth anions with either double O-bridges between the metal centres, [Bi2(μ-pdc-R)2(pdc-R)2(dmf)2][NH2Me2]2 (R = OH, NH2), 4 and 5, or double carboxylate bridges with one long Bi–O bond, [Bi2(μ-pdc-NMe2)2(pdc-NMe2)2(dmf)2][NH2Me2]2, 6 (R = Cl, but replaced by dimethylamine during the reaction). The structures and supramolecular networks of 1–6 are described and compared as an exploration of alternatives to the conventional carboxylate-based organic linking units.