Dong-Xue Xia,Li-Wen Fan,Ming-Fu Ye,Wen-Qi Sun,Rui-Lian Lin,Jing-Xin Liu
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.
Dong-Xue Xia,Chen-Yan Xu,Ming-Fu Ye,Rui-Lian Lin,Jing-Xin Liu
Multi-stimuli-responsive chromic materials have immense potential for utilization. Herein, two supramolecular inclusion complexes were prepared by self-assembly of β-cyclodextrin (β-CD) with dialkylcarboxyl-substituted viologens, N,N′-di(3-carboxy-propyl)-4,4′-bipyridinium dichloride (CPV·Cl2) and N,N′-di(6-carboxy-hexyl)-4,4′-bipyridinium dibromide (CHV·Br2). The self-assembled inclusion complexes CPV2+@β-CD and CHV2+@β-CD2 in the solid-state exhibited naked-eye photochromism, thermochromism, and electrochromism in response to multiple external stimuli including light, temperature, and electric field, respectively. Solid-state UV–vis diffuse reflectance and electron spin resonance (ESR) spectroscopy revealed that the observed photochromism, thermochromism and electrochromism are attributed to the formation of viologen free radicals induced by electron transfer under external stimuli. The excellent stimuli-response chromic properties of the title inclusion complexes support their practical utility in visual display, multiple anticounterfeiting, and multilevel information encryption.
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