Chloroform-selective vapochromic behavior based on crystal-state host-guest complexation of an organic cage

Developing vapochromic materials capable of distinguishing molecules with minimal structural difference is important due to the complexity of environmental monitoring. This work reports an organic cage with vapochromic behavior upon exposure to halogenated methane (CH2Cl2, CHCl3 and CCl4) vapors. The vapochromic response of the organic cage is highly selective towards CHCl3 molecules, although CH2Cl2 and CCl4 molecules have very similar structures. Powder and single-crystal X-ray diffraction analyses reveal that this vapochromic behavior is attributed to the noncovalent interactions between hosts and guests to enhance the cage molecular conjugation, leading to a red-shift of its absorption band in the range of 450-800 nm. This work provides new insights into the design of novel reversible vapochromic systems based on a well-defined discrete organic cage as the main scaffold.

Automated summary

Developing vapochromic materials for distinguishing molecules is important. This study reports an organic cage that exhibits vapochromic behavior when exposed to halogenated methane vapors. The cage selectively responds to CHCl3 molecules, despite their structural similarity to CH2Cl2 and CCl4. The vapochromic behavior is attributed to noncovalent interactions between the hosts and guests, enhancing the cage's molecular conjugation.