Room-temperature phosphorescence of a supercooled liquid: kinetic stabilisation by desymmetrisation,Chemical Science

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Room-temperature phosphorescence of a supercooled liquid: kinetic stabilisation by desymmetrisation
Chemical Science ( IF 7.6 ) Pub Date : 2021-09-10 , DOI: 10.1039/d1sc03800a
Mao Komura ₁ , Takuji Ogawa ₁ , Yosuke Tani ₁

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Achieving organic room-temperature phosphorescence (RTP) in a solvent-free liquid state is a challenging task because the liquid state provides a less rigid environment than the crystal. Here, we report that an unsymmetrical heteroaromatic 1,2-diketone forms an organic RTP liquid. This diketone exists as a kinetically stable supercooled liquid, which resists crystallisation even under pricking or shearing stresses, and remains as a liquid for several months. The unsymmetrical diketone core is flexible, with eight distinct conformers possible, which prevents nucleation and growth for the liquid–solid transition. Interestingly, the thermodynamically stable crystalline solid-state was non-emissive. Thus, the RTP of the diketone was found to be liquiefaction-induced. Single-crystal X-ray structure analysis revealed that the diminished RTP of the crystal is due to insufficient intermolecular interactions and restricted access to an emissive conformer. Our work demonstrates that flexible unsymmetrical skeletons are promising motifs for bistable liquid–solid molecular systems, which are useful for the further development of stimuli-responsive materials that use phase transitions.

中文翻译：

过冷液体的室温磷光：通过去对称作用实现动力学稳定

在无溶剂液态下实现有机室温磷光（RTP）是一项具有挑战性的任务，因为液态提供的环境比晶体不太严格。在这里，我们报道了不对称杂芳族 1,2-二酮形成有机 RTP 液体。这种二酮以动力学稳定的过冷液体形式存在，即使在刺破或剪切应力下也能抵抗结晶，并可在数月内保持液体状态。不对称的二酮核心是灵活的，可能具有八种不同的构象异构体，这可以防止液固转变的成核和生长。有趣的是，热力学稳定的结晶固态是非发射性的。因此，发现二酮的RTP是液化诱导的。单晶 X 射线结构分析表明，晶体的 RTP 降低是由于分子间相互作用不足以及发射构象异构体的获取受到限制。我们的工作表明，柔性不对称骨架是双稳态液-固分子系统的有前途的图案，这对于进一步开发利用相变的刺激响应材料是有用的。

更新日期：2021-09-22

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