Browsing by Author "Melkizedeck Hiiti Tsere"

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Photochromic and fluorescence switching behavior of triazole-functionalized fulgimides: Experimental and theoretical study
(Journal of Luminescence, 2026-05-11) Khamis Nassor Ally; Melkizedeck Hiiti Tsere; Said Ali Vuai; Azaria Stephano Lameck; Leyla Oztürk; Mahmut Kos
Integrating photochromism and fluorescence switching within a single molecular platform remains a central challenge in the development of light-regulated functional materials. Here, we report a structure-encoded design strategy based on the direct covalent incorporation of a 1,2,4-triazole unit into the imide framework of fulgimides, yielding three new photoresponsive molecules (4E–6E). Experimentally, all compounds exhibit photochromism based on the interconversion between open and closed forms. This is accompanied by large visiblerange spectral contrast and reversible fluorescence ON/OFF switching under alternating UV and visible light. The open-ring forms are strongly emissive, while photoinduced cyclization produces systematic fluorescence quenching (20–40%) governed by intramolecular energy transfer to the conjugated closed-ring core. Density functional and time-dependent DFT calculations quantitatively reproduce the observed experimental absorption behavior and reveal pronounced π-delocalization and HOMO-LUMO gap narrowing upon ring closure, establishing clear structure–property relationships. Among the series, compound 6E shows the most favorable electronic and optical characteristics. These results identify triazole-imide coupling as a generalizable molecular engineering route for multifunctional organic photo-switches and advance their potential for optical memory, sensing, and adaptive photonic applications.