School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518055, P. R. China.
J Am Chem Soc. 2021 Jun 23;143(24):9215-9221. doi: 10.1021/jacs.1c04288. Epub 2021 Jun 9.
Materials with aggregation-induced emission (AIE) properties are of growing interest due to their widespread applications. AIEgens, such as tetraphenylethylene units, display varying emission behaviors during their conformational changes. However, the structure-property relationships of the intermediate conformations have rarely been explored. Herein, we show that the conformational restriction on TPE units can affect the structural relaxation in the excited state and the resulting photophysical behaviors. Specifically, three metallacages of different sizes were prepared via the coordination-driven self-assembly of a TPE-based tetrapyridyl donor with length-increasing Pt(II) acceptors. While the metallacages share similar scaffolds, they exhibit a trend of red-shifted fluorescence and attenuated quantum yield with the increase of their sizes. Furthermore, spectroscopic and computational studies together with a control experiment were conducted, revealing that the degree of cage tension imposed on the excited-state conformational relaxation of TPE moieties resulted in their distinct photophysical properties. The precise control of conformation holds promise as a strategy for understanding the AIE mechanism as well as optimizing the photophysical behaviors of materials on the platform of supramolecular coordination complexes.
具有聚集诱导发光（AIE）性质的材料因其广泛的应用而受到越来越多的关注。AIE gens，如四苯乙烯单元，在构象变化过程中表现出不同的发光行为。然而，中间构象的结构-性质关系很少被探索。在此，我们表明 TPE 单元的构象限制可以影响激发态中的结构弛豫和由此产生的光物理行为。具体来说，通过基于 TPE 的四吡啶供体与长度增加的 Pt(II)受体的配位驱动自组装，制备了三种不同尺寸的金属笼。虽然金属笼具有相似的支架，但它们的荧光红移和量子产率随尺寸的增加而减弱。此外，进行了光谱和计算研究以及对照实验，揭示了金属笼对 TPE 部分激发态构象弛豫施加的紧张程度导致了它们不同的光物理性质。精确控制构象有望成为理解 AIE 机制以及优化基于超分子配位配合物平台的材料光物理行为的一种策略。
