Understanding the Effects of Coordination and Self-Assembly on an Emissive Phenothiazine.
Understanding the Effects of Coordination and Self-Assembly on an Emissive Phenothiazine.
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DOI：
10.1021/jacs.9b00363
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发表时间：
2019-01
影响因子：
15
通讯作者：
Zhixuan Zhou;Cory E. Hauke;B. Song;Xiaopeng Li;P. Stang;Timothy R. Cook
中科院分区：
文献类型：
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作者：
Zhixuan Zhou;Cory E. Hauke;B. Song;Xiaopeng Li;P. Stang;Timothy R. Cook
发光体周围的局部环境可以显著地影响它们的光物理性质。在这里，我们报告的自组装的高发射性铂（II）为基础的metallacage。为了适应在自组装过程中使用的铂（II）构建块的连接性，含发光体的构建块相对于其自由形式采用高度扭曲的几何形状，导致出现具有比自由发光体高一个数量级的辐射速率常数的发射跃迁。这种增加的速率常数是量子产率从4.2%增加到40%的10倍的主要驱动力。合成了具有与氮结合的铂或甲基的模型配合物。这些配合物具有较低的量子产率（10%和非发射，分别），主要是由于辐射速率常数的降低。进行了计算研究，并表明，激发态的合奏，以及模型复合物，是一个结果的电荷转移到吡啶基，相反的自由发光体，其中涉及的二苯砜部分。量子产率的差异可以解释为在吡啶基上的铂或甲基化的配位后，发色团中的扭曲，导致系统间交叉到三重态。这种状态在添加铂后变得更加发射，这通过重原子效应增加了辐射速率常数。金属笼的形成还通过抑制所并入的发光体的分子内运动来降低非辐射速率常数。
The local environment surrounding luminophores can significantly influence their photophysical properties. Herein, we report the self-assembly of a highly emissive platinum(II)-based metallacage. In order to accommodate the connectivity of the platinum(II) building block used in the self-assembly process, the luminophore-containing building block adopts a highly twisted geometry relative to its free form, leading to the emergence of an emissive transition with a radiative rate constant an order of magnitude higher than that of the free luminophore. This increased rate constant is the primary driver for the 10-fold increase in quantum yield from 4.2% to 40%. Model complexes with platinum or methyl groups bound to the nitrogen were synthesized. These complexes had lower quantum yields (10% and non-emissive, respectively) due mainly to decreases in radiative rate constants. Computational studies were conducted and indicated that the excited state of the ensembles, as well as the model complexes, is a result of charge transfer to the pyridyl groups, in contrast to the free luminophore, which involves the diphenyl sulfone moiety. The differences in quantum yields can be explained by a twist in the chromophore upon coordination of platinum or methylation on the pyridyl group, leading to intersystem crossing to a triplet state. This state then becomes more emissive with the addition of platinum, which increases the radiative rate constant via the heavy atom effect. The formation of a metallacage also decreases the non-radiative rate constant by inhibiting the intramolecular motions of the incorporated luminophore.