Key points are not available for this paper at this time.
Colored crystals of pillar5arene containing one benzoquinone unit were found to exhibit alkane-shape-selective vapochromic behavior. Activated pillar5arene crystals, prepared by removing solvated methanol from pillar5arene crystals, changed color from dark-brown to light-red after exposure to linear alkane vapors; however, no color changes were observed on exposure to branched or cyclic alkanes. Uptake of methanol vapor by the activated crystals induced a different color change, from dark-brown to black. This multi-vapochromism results from the different intermolecular π-stacking interactions between the benzoquinone and 1,4-diethoxybenzene units in the alkane- and methanol-containing crystals. Unlike most known vapochromic materials, these pillar5arene-based materials were highly stable; after uptake of n-alkanes or methanol the color of the crystals did not change after storage in air for 3 weeks. This is because the included guests were stabilized in the cavity by multiple CH/π interactions.
Ogoshi et al. (Mon,) studied this question.