Modulation of charge transfer by N-alkylation to control photoluminescence energy and quantum yield.
Modulation of charge transfer by N-alkylation to control photoluminescence energy and quantum yield.
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DOI：
10.1039/d0sc02460k
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发表时间：
2020-06-09
期刊：
影响因子：
8.4
通讯作者：
Etherington MK
中科院分区：
文献类型：
--
作者：
Turley AT;Danos A;Prlj A;Monkman AP;Curchod BFE;McGonigal PR;Etherington MK
有机荧光团中的电荷转移是基本的电子物理过程，其可以是有益的，例如，促进热激活延迟荧光，或有害的，例如，介导发射猝灭。N-烷基化被证明提供直接的合成控制的电荷转移，发射能量和量子产率的胺发色团。我们使用奎宁作为模型来证明这个概念。N-烷基化引起其发射的变化，其反映了由pH变化引起的那些（即，质子化）。然而，与质子化不同的是，奎宁的两个N位点的烷基化是以逐步的方式进行的，以得到动力学稳定的物种。这种动力学稳定性使我们能够分离和表征的N-烷基化类似物的一个“非自然”的质子化状态，是季铵化选择性地在碱性较低的网站，这是不可访问的使用酸。这些材料暴露了（i）奎宁的空间电荷转移激发态和（ii）相关的损失途径，同时（iii）开发了一种简单的盐，其性能优于硫酸奎宁作为量子产率标准。这种N-烷基化方法可以广泛应用于通过调节电荷转移态来发现发光材料。一种通用的N-烷基化策略控制电荷转移激发态的存在和N-杂环发色团的发射颜色。
Charge transfer in organic fluorophores is a fundamental photophysical process that can be either beneficial, e.g., facilitating thermally activated delayed fluorescence, or detrimental, e.g., mediating emission quenching. N-Alkylation is shown to provide straightforward synthetic control of the charge transfer, emission energy and quantum yield of amine chromophores. We demonstrate this concept using quinine as a model. N-Alkylation causes changes in its emission that mirror those caused by changes in pH (i.e., protonation). Unlike protonation, however, alkylation of quinine's two N sites is performed in a stepwise manner to give kinetically stable species. This kinetic stability allows us to isolate and characterize an N-alkylated analogue of an ‘unnatural’ protonation state that is quaternized selectively at the less basic site, which is inaccessible using acid. These materials expose (i) the through-space charge-transfer excited state of quinine and (ii) the associated loss pathway, while (iii) developing a simple salt that outperforms quinine sulfate as a quantum yield standard. This N-alkylation approach can be applied broadly in the discovery of emissive materials by tuning charge-transfer states. A versatile N-alkylation strategy controls the presence of charge-transfer excited states and the emission colour of N-heterocyclic chromophores.
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影响因子：
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作者：
BRUNSCHWIG, BS;EHRENSON, S;SUTIN, N
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