Coordinatively polymeric and monomeric bismuth(iii) complexes with pyridine carboxylic acids

Abstract

Three crystalline compounds, [Bi(2-O₂C–C₅H₄N)₃]_n (1), {Bi[(2,6-O₂C)₂C₅H₃N)][(2-HO₂C-6-O₂C)C₅H₃N]·H₂O}_n (2) and Bi(O₂CC₉H₆N)₂(O₃N)(O₂CC₉H₆NH)·2H₂O (3) have been prepared by simple reactions in aqueous medium using the readily available bismuth nitrate and the corresponding acids, picolinic acid, dipicolinic acid and quinaldic acid. While 1 and 2 are coordination polymers with bismuth in tricapped trigonal prismatic and dodecahedral environments, compound 3 is a monomeric species with dodecahedral geometry at bismuth. Compound 1 represents a second crystalline form of a recently reported structure with subtle differences in bond parameters, and highlights the flexibility in structural motifs during crystallization. Compound 2 involves skeletons with dimeric [Bi₂O₂] and trimeric [BiOCOBiOBiOCO] moieties. In 3, while the N-protonated carboxylate forms a four-membered chelate ring with bismuth, the other two carboxylates form five-membered ring chelates with the nitrate accounting for the remaining two sites again as a chelate. TGA studies are consistent with the presence of non-coordinated water in 2 and 3. Compounds 1 and 2, although insoluble in most of the organic solvents and water, are readily soluble in dilute hydrochloric acid.