Abstract Organic room temperature phosphorescence (RTP) molecules have attracted significant attention recently due to their promising application in security, bioimaging, sensing and organic light emitting diodes (OLEDs). Nevertheless, limited RTP molecules were reported until now and most of RTP phenomena were observed in crystal. Moreover, the underlying mechanisms of RTP still remain ambiguous. In this paper, excited-state properties of CZs-CN with RTP features in three crystals are theoretically studied using the combined quantum mechanics and molecular mechanics (QM/MM) method. Moreover, the photophysical properties of CZs-CN in solvent are also investigated by polarizable continuum model (PCM). The mechanism of aggregation induced RTP is revealed which is mainly contributed by the enhanced phosphorescence rates in aggregation, rather than the traditional restricted intramolecular motion mechanisms which usually bring decreased non-radiative decay rates. In addition, different crystal structures could induce different phosphorescence properties, and the emission spectra of the molecule in three crystals and THF are explained reasonable. Furthermore, dimers are confirmed to be involved in the emission when the intermolecular interaction is strong enough in aggregation. Our theoretical results provide inner perspective for aggregation induced RTP mechanism and could help one to better understand the different light-emitting properties in aggregation and solvent.

中文翻译：

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关于聚集诱导的室温磷光特性的见解：QM/MM 研究

摘要 有机室温磷光 (RTP) 分子由于其在安全、生物成像、传感和有机发光二极管 (OLED) 中的应用前景而备受关注。然而，迄今为止报道的 RTP 分子有限，并且大多数 RTP 现象都在晶体中观察到。此外，RTP 的潜在机制仍然不明确。本文采用量子力学和分子力学相结合的方法（QM/MM）从理论上研究了三种晶体中具有RTP特征的CZs-CN的激发态性质。此外，还通过可极化连续介质模型（PCM）研究了 CZs-CN 在溶剂中的光物理性质。揭示了聚集诱导 RTP 的机制，这主要是由于聚集中磷光率的提高，而不是通常会降低非辐射衰减率的传统受限分子内运动机制。此外，不同的晶体结构会引起不同的磷光特性，并且三种晶体中分子的发射光谱和THF得到了合理的解释。此外，当分子间相互作用在聚集中足够强时，证实二聚体参与发射。我们的理论结果为聚集诱导的 RTP 机制提供了内在视角，有助于更好地理解聚集和溶剂中不同的发光特性。并且三晶体中分子的发射光谱和THF得到了合理的解释。此外，当分子间相互作用在聚集中足够强时，证实二聚体参与发射。我们的理论结果为聚集诱导的 RTP 机制提供了内在视角，有助于更好地理解聚集和溶剂中不同的发光特性。并且三晶体中分子的发射光谱和THF得到了合理的解释。此外，当分子间相互作用在聚集中足够强时，证实二聚体参与发射。我们的理论结果为聚集诱导的 RTP 机制提供了内在视角，有助于更好地理解聚集和溶剂中不同的发光特性。