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The crystal structures of 1-(2,3,5,6-tetrafluoro-4-pyridyl)-3-benzylimidazolium chloride (<b>1</b>) and iodide (<b>3</b>) have been determined by single crystal X-ray diffraction. The crystal structure of <b>1</b> is similar to that of the bromide salt (<b>2</b>), possessing anion···C₅F₅N···C₆H₅ motifs, whilst that of <b>3</b> contains columns of alternating iodide anions and parallel tetrafluoropyridyl rings. All three crystal structures possess C(1)–H∙∙∙X⁻ and C(2)–H∙∙∙X⁻ hydrogen bonding. DFT calculations reveal that the strengths of the hydrogen bonding interactions lie in the order C(1)–H···X⁻ > C(3)–H···X⁻ > C(2)–H···X⁻ for the same halide (X⁻) and Cl⁻ > Br⁻ > I⁻ for each position. It is suggested that salt <b>3</b> adopts a different structure to salts <b>1</b> and <b>2</b> because of the larger size of iodide.