cis-trans Isomerism Enables Visible Light-Excited Room-Temperature Phosphorescence and Dynamic Afterglow.

Abstract

Isomerism serves as a powerful strategy for modulating organic room-temperature phosphorescence (RTP), which is crucial for developing novel RTP materials and elucidating structure-property relationships. However, cis-trans isomerism that is widespread in organic compounds has not been deeply explored in terms of its influence on RTP properties. In this study, the cis-trans isomers of two 9,10-dihydrophenanthrene-9,10-dicarbonitriles, DPCN-H and DPCN-O (with OMe group), are designed and synthesized. Significant differences in luminous behavior are observed between the cis- and trans-isomers. The trans-DPCNs exhibit notably superior RTP and afterglow performance compared to cis-DPCNs for their better structural planarity and tighter packing. Among them, trans-DPCN-O achieves an afterglow quantum yield as high as 43% upon visible-light excitation. Additionally, trans-DPCN-H displays excitation-power-dependent and temperature-dependent afterglow color modulation, while the nanoparticles of trans-DPCN-O demonstrates efficient visible-light-excited afterglow in aqueous solution. The excellent RTP properties of the trans-DPCNs enable their successful application in complex anti-counterfeiting with four dimensions, and in vivo imaging in mice under white LED excitation with a signal-to-noise ratio of up to 228. This work presents the first investigation into how cis-trans isomerism affects organic RTP and provides new insights into designing high-performance RTP materials.

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