Structural Diversity of Bismuth(III) Thiophenemonocarboxylates Isolated from Aqueous Solutions.

Five novel BiIII-thiophenemonocarboxylate (BiIII-TMC) compounds containing pyridinium cations have been synthesized from room-temperature reactions of bismuth precursors with 2-thiophenecarboxylic acid (HTMC) and pyridine in water. The structures have been determined by single-crystal Xray diffraction, and two of the compounds have been further characterized by Raman spectroscopy and thermogravimetric analysis. The solid-state structures of the compounds are built from anionic BiIII building units that vary in nuclearity, overall connectivity, and dimensionality. When using bismuth nitrate at a relatively low metal/ligand ratio, Hpy[Bi(TMC)4(HTMC)] (1) is formed, which consists of mononuclear units charge-balanced by second coordination sphere pyridinium cations. With increasing metal/ligand ratios, and by consequence, increasing nitrate concentration, nitrate and carboxylate-bridged chains of [Bi2(TMC)3(NO3)]- units in Hpy[Bi2(TMC)6(NO3)] (2), and nitratebridged [Bi2(TMC)3(NO3)2]2- dimers in Hpy[Bi(TMC)3(NO3)] (3) are isolated. Starting from Bi2O3, polymorphs (Hpy)2[Bi2(TMC)8] (4) and (Hpy)2[Bi2(TMC)8] (5) are formed, both of which contain bismuth centers bridged by carboxylate groups to form dimeric units that are charge-balanced by pyridinium cations. Presented herein is a discussion of the synthetic conditions over which 1-5 were isolated, and their solid-state structural chemistry. The thermal stability of 1 and 3, and the spectroscopic characterization of the compounds, are also reported. [ABSTRACT FROM AUTHOR]