Interhalogen 1,2,3-Triazolium Ionic Liquid: Synthesis, Crystal Structure, Hirshfeld Surface Analysis and Photophysical Properties

A new interhalogen ionic liquid [C17H25N3Br](+)[IBr2](-) (IL-1) was synthesized from its triazolium iodide precursor [C17H26N3+](-)] in THE under cold and basic conditions. X-ray diffraction data showed that IL-1 is composed of two moieties contained in a triclinic unit cell; the five-membered triazolium cation and an almost linear iodidobromide anion, IBr2-. The Br atoms of the anion form quadfurcated C-H center dot center dot center dot Br hydrogen bonds with neighbouring cationic halo-1,2,3-triazolium H-species. Intermolecular Br center dot center dot center dot Br halogen bonds and I center dot center dot center dot pi(triazole) interactions form a distinctive ring-like pattern that links together four molecular units in the crystal packing. Hirshfeld surface analysis revealed that the most significant d(norm) surface contribution at 59% is due to H center dot center dot center dot H and reciprocal C center dot center dot center dot H contacts, while the Br center dot center dot center dot Br contacts only contributed 3%. The prevalence of extensive H center dot center dot center dot H and C center dot center dot center dot H contacts is potentially due to the linear aliphatic chain, the N-octyl wingtip substituent of the triazolyl moiety. The Hirshfeld surface mapping also shows the contribution of intermolecular C-H center dot center dot center dot Br interactions at 26% of all contacts. The title compound (IL-1) showed interesting photophysical properties in MeCN solution, with an absorption band at 254 nm and two-shoulder emission bands due to strong pi ->pi* transitions from the triazolium moiety, indicating the presence of two energetically associated species. [GRAPHICS] .