Kongasseri Anju Ajayan, Ansari Shagufi Naz, Garain Swadhin, Wagalgave Sopan M, George Subi J
New Chemistry Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) Jakkur Bangalore 560064 India
Chem Sci. 2023 Oct 31;14(44):12548-12553. doi: 10.1039/d3sc04001a. eCollection 2023 Nov 15.
Simple and efficient designs that enable a wide range of phosphorescence emission in organic materials have ignited scientific interest across diverse fields. One particularly promising approach is the cocrystallization strategy, where organic cocrystals are ingeniously formed through relatively weaker and dynamic non-covalent interactions. In our present study, we push the boundaries further by extending this cocrystal strategy to incorporate donor-acceptor components, stabilized by various halogen bonding interactions. This non-covalent complexation triggers ambient, charge-transfer phosphorescence (CT), which can be precisely tuned across a broad spectrum by a modular selection of components with distinct electronic characteristics. At the core of our investigation lies the electron-deficient phosphor, pyromellitic diimide, which, upon complexation with different donors based on their electron-donating strength, manifests a striking array of phosphorescence emission from CT triplet states, spanning from green to yellow to reddish orange accompanied by noteworthy quantum yields. Through a systematic exploration of the electronic properties using spectroscopic studies and molecular organization through single-crystal X-ray diffraction, we decisively establish the molecular origin of the observed phosphorescence. Notably, our work presents, for the first time, an elegant demonstration of tunable CT phosphorescence emission in intermolecular donor-acceptor systems, highlighting their immense significance in the quest for efficient organic phosphors.
能够在有机材料中实现广泛磷光发射的简单高效设计引发了各个领域的科学兴趣。一种特别有前景的方法是共结晶策略，即通过相对较弱且动态的非共价相互作用巧妙地形成有机共晶体。在我们目前的研究中，我们进一步拓展了这一界限，将这种共晶体策略扩展到纳入供体 - 受体组分，并通过各种卤键相互作用使其稳定。这种非共价络合引发了室温下的电荷转移磷光（CT），通过模块化选择具有不同电子特性的组分，可以在很宽的光谱范围内对其进行精确调节。我们研究的核心是缺电子磷光体均苯四甲酸二酰亚胺，它与基于给电子强度的不同供体络合时，会从CT三重态表现出一系列引人注目的磷光发射，从绿色到黄色再到红橙色，同时伴有可观的量子产率。通过使用光谱研究对电子性质进行系统探索以及通过单晶X射线衍射对分子结构进行研究，我们明确地确定了观察到的磷光的分子起源。值得注意的是，我们的工作首次展示了分子间供体 - 受体体系中可调谐CT磷光发射的精妙示例，突出了它们在寻求高效有机磷光体方面的巨大意义。
