Self-recovering mechanochromic luminescence of the derivatives of benzanthrone and carbazole: Towards damage-resistive information recording and security probes

Discovery of organic luminophores with unique properties typically leads to new applications of such emitters in the field of organic optoelectronics. The example is demonstrated in this study. One of the newly synthesized mechanochromic derivatives of benzanthrone and carbazole demonstrates ability of self-regulation of its solid-state structure and related light-emitting properties. This compound shows intensive green emission peaking at 537 nm in the initial state, weak yellowish green emission peaking at 557 nm after mechanical treatment which self-recovers back to intensive green emission with the intensity maximum at 539 nm. The processes are completely reversible. They include the following set of states: highly emissive state → damaged weak-emissive state → self-recovering → recovered highly emissive state. The developed compound is a very rare example of materials which can be used for security probes or data/code writing with recovering ability after mechanical damage. Variety of experimental studies including spectroscopy of thermally annealed samples and single crystal and powder diffraction X-ray analysis revealed the ability of the developed derivatives of benzanthrone and carbazole to form different polymorphs and aggregates in solid-state responsible for their multicolour mechanochromic emission.