Abstract
Three new mercury(II) coordination compounds, {[HgCl(pic)]}n (1), [HgCl(pic)(picH)] (2), and [HgBr(pic)(picH)] (3) (picH = pyridine-2-carboxylic acid, picolinic acid) were prepared by reactions of the corresponding mercury(II) halides and picolinic acid in an aqueous (1) or alcohol–methanol or ethanol (2 and 3) solutions. Two different types of coordination compounds were obtained depending on the solvent used. The crystal structures were determined by the single-crystal X-ray structural analysis. Compound 1 is a one-dimensional (1-D) coordination polymer with mercury(II) ions bridged by chelating and bridging N,O,O′-picolinate ions. Each mercury(II) ion is four-coordinated with a bidentate picolinate ion, a carboxylate O atom from the symmetry-related picolinate ion and with a chloride ion; the resulting coordination environment can be described as a highly distorted tetrahedron. Compounds 2 and 3 are isostructural mononuclear coordination compounds, each mercury(II) ion being coordinated with the respective halide ion, N,O-bidentate picolinate ion, and N,O-bidentate picolinic acid in a highly distorted square-pyramidal coordination environment. Compounds 1–3 were characterized by IR spectroscopy, PXRD, and thermal methods (TGA/DSC) in the solid state and by 1H and 13C NMR spectroscopy in the DMSO solution.
Highlights
The transition metal coordination compounds have been of great interest over the past decades because of their interesting and diverse structural features and promising applications in different fields of industry
The reactions of mercury(II) chloride and bromide with picolinic acid were studied in aqueous, methanol and ethanol solutions to see how the solvent change and metal-to-ligand ratio would affect the obtained complexes (Scheme 1)
The neighboring mercury(II) ions are bridged by an N,O,O0 -picolinate ion into a polymeric chain of 1, while both complexes 2 and 3 are mononuclear, containing the respective halide ion and N,O-bidentate picolinate ion and picolinic acid molecule
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The transition metal coordination compounds have been of great interest over the past decades because of their interesting and diverse structural features and promising applications in different fields of industry Such compounds can be used in various areas as materials that exhibit desired catalytic, ion-exchange, gas storage, pharmaceutical, luminescence, optical, electronic, or magnetic properties [1,2,3,4,5,6,7,8,9]. As it became evident that slight changes in the preparation procedures (e.g., metal-to-ligand ratio, solvent choice, pH of the solution, temperature) of mercury(II) complexes with picolinate and its derivatives lead to complexes of various compositions and dimensionalities, the possibility of obtaining new picolinate mercury(II) complexes under defined experimental conditions needed to be examined further.
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