Chiral Dual Core Chromophores Based on Binaphthyl Acrylonitrile Motif with Tunable Dual Emission Bands and Anti-counterfeiting

Small organic molecules which can emit fluorescence with tunable dual emission bands are significant for fundamental research and broad applications. In this work, two binaphthyl based arylacrylonitrile derivatives with pyrene and triphenylamine unit (BiNp-Py and BiNp-TPA) were designed and synthesized, respectively, featuring chiral backbone and dual AIE-active cyanostyrene-linked chromophores. Excellent fluorescence emissions in a range of solution and solid states were observed with high quantum yields, indicative of the solvatochromism and mechanochromism. More interestingly, dual emission bands were found and tunable by the water fraction in THF, and speculatively attributed to the balancing of intramolecular charge transfer (ICT) and locally excited (LE) emission in solution and aggregate states. Furthermore, the potential application in anti-counterfeiting ink was also explored, indicating the very low concentration (5 ppm) for sufficient distinguishable vision and small colour migration (28 nm) for printing on the filter. The present work provides a new strategy to design organic luminescent structure having widely fluorescent emissions in dual states and a valuable reference for the study of chiral optical materials. The prepared chiral dual core chromophores based on binaphthyl acrylonitrile were shown to have the excellent dual state emissions and tunable dual wavelength emissions. A range of colors could be observed by solvatochromic and mechanochromic effects, and the anti-counterfeiting application with small color migration was also achieved.image

Automated summary

In this study, two new organic molecules were designed and synthesized, which exhibit excellent fluorescence emissions with tunable dual emission bands in both solution and solid states. The water fraction in THF was found to have an effect on the tuning of emission bands. Additionally, the potential application of these molecules in anti-counterfeiting ink was explored.