Photo-induced room temperature phosphorescence and thermally activated photochromism based on thianthrene derivatives

Abstract

In the field of smart materials, designing organic compounds that exhibit both photo-induced room temperature phosphorescence (RTP) and photochromism presents significant challenges. Despite this, the broad potential applications of such materials continue to attract substantial interest from the scientific community. Here, we engineered three thianthrene derivatives by modifying the π-conjugation, creating the polymer-doped systems TN-2Me-p, TN-PhNap-p, and TN-2Nap-p, each with both photo-induced RTP and reversible, reusable photochromic properties. Notably, the poly(methyl methacrylate) film doped with TN-2Nap (TN-2Nap-p), a molecule featuring two naphthyl groups, displayed remarkable thermally erasable photochromism with an RTP lifetime of 431 ms. In contrast, TN-2Me-doped film, with its naphthyl groups replaced by methyl groups, showed no photochromism under UV exposure but exhibited an increased photoluminescent quantum yield from 3.67% to 13.92%, and an emission lifetime of 132.58 ms. Strikingly, the photochromic response of TN-2Nap-p showed a significant temperature dependency due to radical generation. At room temperature, the radical lifetime was 272.44 s, but decreased 125-fold to 1.76 s at 80 °C. No photochromic activity was observed in liquid nitrogen. Utilizing the distinctive properties of photoinduced RTP and/or thermally activated photochromism, these materials have been successfully applied in mask-based graphic and text writing. Their high quantum yields, exceptional processability, and flexibility also highlight their potential for integration into flexible display technologies.