The Influence of the Halide in the Crystal Structures of 1-(2,3,5,6-Tetrafluoro-4-pyridyl)-3-benzylimidazolium Halides

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

Automated summary

The crystal structures of two compounds containing multiple elements were determined, and the study found structural differences between them. The strength of hydrogen bonding was found to be related to the type of halide present in the compounds.