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The asymmetric unit of the title barium coordination polymer, [Ba(C6H2N3O7)2(C2H6OS)] n , consists of a barium cation (site symmetry m) and a dimethyl sulfoxide (DMSO) ligand (point group symmetry m) and a 2,4,6-trinitrophenolate anion located in general positions. The S atom and the methyl group of DMSO are disordered over two sets of sites. The DMSO ligand bridges a pair of BaII atoms resulting in a chain extending parallel to the a axis. The unique 2,4,6-trinitrophenolate anion also bridges a pair of BaII ions via the phenolic oxygen atom, with each BaII being additionally bonded to an oxygen atom of an adjacent nitro group. The μ 2-monoatomic bridging binding mode of both types of ligands results in the formation of an infinite chain of face-sharing {BaO10} polyhedra flanked by the remaining parts of the 2,4,6-trinitrophenolato and DMSO ligands. In the one-dimensional coordination polymer, parallel chains are interlinked with the aid of C—H...O hydrogen bonds.

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The dissolution of alkaline-earth metal carbonate in aqueous picric acid followed by reaction with nicotinamide results in the formation of [M(H2O) n (nic)2(pic)2] (nic = nicotinamide; pic = picrate; n = 1 and M = Ba 1; n = 2 and M = Ca (or Sr) 2 (or 3)). In [Ba(H2O)(nic)2(pic)2] 1, the barium and the oxygen atoms of a terminal aqua ligand are located on a two-fold axis. Compound 1 exhibits a {BaO7N2} coordination sphere, where the barium atom is bonded to a unique bidentate picrate and the crystallographically independent nicotinamide bridges to two symmetry related barium atoms with a Ba···Ba separation of 9.799 Å via the pyridine nitrogen and the amide oxygen atoms leading to the formation of a two-dimensional coordination polymer. The compounds 2 and 3 are isostructural with discrete molecules. The central Ca atom in 2 (or Sr in 3) located on a two-fold axis is bonded to a crystallographically unique terminal aqua ligand, an independent monodentate nicotinamide and a unique bidentate picrate anion resulting in a distorted {MO8} polyhedron. The mixed ligand alkaline-earth metal picrates 1–3 exhibit three varieties of hydrogen bonding and π–π stacking interactions. Several alkaline-earth metal picrates are compared in this study.