Reversible color switching of bright phosphorescence in purely organic materials for advanced data encryption.

Heo, Jung-Moo; Woo, Hochul; Flórez-Angarita, Maria F; Park, Jihyun; Milián-Medina, Begoña; Matzger, Adam J; Gierschner, Johannes; Kwon, Min Sang et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

Purely organic phosphors have emerged as promising materials for various optical applications. Herein, we report a single-component organic phosphorescent crystal, 1,1'-(2,5-dibromoterephthaloyl)bis(glutarimide) (BrGlu), which exhibits fully reversible, pseudopolymorph-dependent phosphorescence color switching. Under standard crystallization conditions, BrGlu forms green-emitting crystal (G-crystal), while crystallization in the presence of CHCl<sub>3</sub> yields blue-emitting solvent-inclusion crystal (B-crystal). Notably, G-crystal converts into B-crystal upon exposure to CHCl<sub>3,</sub> whereas the blue crystals revert to green upon heating, demonstrating a reversible phosphorescence-to-phosphorescence switching mechanism. Through a combination of experimental analyses and quantum chemical calculations, we elucidate the underlying mechanism governing this triplet emission color transformation: syn-anti conformational reorientation of bromine-carbonyl substituents: upon solvent inclusion, hydrogen bonding stabilizes the syn-rotamer to yield bright-blue phosphorescence, whereas gentle heating reverts the system to the anti-rotamer for green emission. Exploiting this property, we develop an advanced data encryption platform featuring a dual-layer security system-phosphorescence emission combined with thermal- or solvent-induced stimuli-response-significantly enhancing security in secure data encryption and anti-counterfeiting.