Imidazolium Ionic Liquid-Functionalized Extended Pillar[6]Arene with High Selectivity for Gas-Chromatographic Separations

Pillar[n]arenes (n = 5–10), novel macrocycles, are gaining prominence in supramolecular studies owing to their distinctive three-dimensional architecture featuring a π-electron-rich cavity and have emerged as a key synthetic macrocyclic host in research. Extended pillar[n]arenes (Ep[n]As) notably feature sizable internal voids, adaptable structures, versatile cavity shapes, and ease of synthesis. This work presents the first example of imidazolium ionic liquid-functionalized Ep[n]As (BpP6A-C10-IM-C8[NTf2]) as a gas chromatography stationary phase. The BpP6A-C10-IM-C8[NTf2] column was prepared by the static method, exhibiting medium polarity and high column efficiency (4660 plates/m, k = 2.29). The separation performance of the prepared column was evaluated for analytes, including a mixture of 22 analytes, more than 12 positional isomers, and 8 cis-/trans-isomers. Furthermore, the chromatograms of the challenging isomers of bromonitrobenzenes, chloronitrobenzenes, bromobenzaldehydes, toluidines, and dimethylanilines on the BpP6A-C10-IM-C8[NTf2] column were compared with those on the BpP6A-C10 column and commercial HP-5 and HP-35 columns. The BpP6A-C10-IM-C8[NTf2] column also showed high selectivity for biphenyl isomers, including methylbiphenyls, iodobiphenyls, and bromobiphenyls.