Superstructure-induced enhancement of solid-state triphenylacrylonitrile photochromism via a macrocycle-mediated blocking strategy

Abstract

Developing materials with precisely tunable photochromic properties is crucial for innovative applications, and this requires rational design strategies to overcome photoisomerization constraints imposed by molecular stacking. Herein, we introduce a pillararene-based “blocker” strategy to mitigate π–π stacking of photoisomerizable molecules. The pillararene entity facilitates photochromic chromophore torsion by providing free volume and stabilizes photoisomerization products in conjunction with specific volatile organic compounds (VOCs) through supramolecular interactions. With this strategy, we obtain a solid-state photochromic material induced by VOCs, exhibiting reversible white-to-red color changes. This material's enhanced photochromic behavior, especially when exposed to oxygen-containing VOCs, such as CH₃OH, HCOOH, and ethyl acetate, expands its potential applications in UV printing, anti-counterfeiting, and multi-dimensional information encryption. Leveraging the pillar-shaped structure and molecular recognition abilities of pillararenes, this study offers a straightforward strategy for the design of multi-stimuli-responsive photochromic molecules and functional supramolecular macrocycles.