Supramolecular inclusion complexes of β-cyclodextrin with bathochromic-shifted photochromism and photomodulable fluorescence enable multiple applications

Abstract

Three distinct viologen derivatives have been designed and successfully synthesized. They have been shown to form 1 : 1 or 2 : 1 host–guest inclusion complexes with β-cyclodextrin (β-CD) in aqueous solution. In comparison with the traditional N-alkyl-substituted viologen, the inclusion complexes of the conjugation-extended viologens with β-CD exhibit interesting bathochromic-shifted photochromic behaviors in the solid state, which have been characterized by UV-vis diffuse-reflectance and electron-spin resonance (ESR) spectroscopy. Owing to the bathochromic-shift effect, the photoproducts of these three inclusion complexes undergo significant color changes from blue to green and then to orange. In addition, these three inclusion complexes display interesting photomodulable fluorescence emissions. The excellent photochromic and fluorescence properties of these three inclusion complexes endow them with potential applications in protection, erasable inkless multi-color printing, multiple anti-counterfeiting and multilevel information encryption, which have also been extensively demonstrated in this work.