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Intramolecular Electron Transfer in Frozen Solvents: Charge Transfer and Local Triplet States Population Dynamics Revealed by Dual Phosphorescence
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2017-09-14 00:00:00 , DOI: 10.1021/acs.jpclett.7b02020 Jerzy Karpiuk 1 , Alina Majka 2 , Ewelina Karolak 2 , Jacek Nowacki 1
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2017-09-14 00:00:00 , DOI: 10.1021/acs.jpclett.7b02020 Jerzy Karpiuk 1 , Alina Majka 2 , Ewelina Karolak 2 , Jacek Nowacki 1
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In frozen solvents at 77 K, ultrafast (≤250 fs) photoinduced intramolecular electron transfer (ET) in bichromophoric donor–acceptor ([D–A]) diarylmethane lactones produces a covalently linked radical ion pair, 1[D•+–A•–]. Steady state and time-resolved luminescence measurements reveal that 1[D•+–A•–] decays to charge-separated (3[D•+–A•–]) and donor-centered ([3D*–A]) triplets, which display dual phosphorescence. 3[D•+–A•–] and [3D*–A] are formed in parallel via two intersystem crossing mechanisms: spin orbit charge transfer (SOCT) and hyperfine coupling (HFC), with solvent dependent branching ratio. The solvent drives the D–A alignment during the freezing process to adapt to increasing solvent polarity, producing inhomogeneous ground-state population distribution with solvent-dependent D–A exchange interaction, which plays a key role in partitioning into SOCT and HFC mechanisms. In polar glasses, a third phosphorescence band appears due to dissociative back ET in 3[D•+–A•–] resulting in excited open ring biradical.
中文翻译：
冷冻溶剂中的分子内电子转移：双重磷光显示的电荷转移和局部三重态种群动态
在77 K的冷冻溶剂中，双发色供体-受体（[D–A]）二芳基甲烷内酯中的超快（≤250fs）光诱导分子内电子转移（ET）产生共价连接的自由基离子对1 [D •+ –A • – ]。稳态和时间分辨的发光测量结果显示1 [D •+ –A •– ]衰减到电荷分离（3 [D •+ –A •– ]）并以供体为中心（[ 3 D * –A]）三胞胎，显示双重磷光。3 [D •+ –A •– ]和[ 3D * –A]是通过两个系统间交叉机制并行形成的：自旋轨道电荷转移（SOCT）和超精细偶合（HFC），其溶剂依赖性支化比。溶剂在冷冻过程中驱动D–A排列，以适应增加的溶剂极性，产生非均质的基态种群分布，并具有溶剂依赖性的D–A交换相互作用，这在划分为SOCT和HFC机制中起着关键作用。在极地眼镜中，由于3 [D •+ –A •– ]中的解离后ET，出现了第三个磷光带，从而导致开环双自由基激发。
更新日期：2017-09-14
中文翻译：
冷冻溶剂中的分子内电子转移：双重磷光显示的电荷转移和局部三重态种群动态
在77 K的冷冻溶剂中，双发色供体-受体（[D–A]）二芳基甲烷内酯中的超快（≤250fs）光诱导分子内电子转移（ET）产生共价连接的自由基离子对1 [D •+ –A • – ]。稳态和时间分辨的发光测量结果显示1 [D •+ –A •– ]衰减到电荷分离（3 [D •+ –A •– ]）并以供体为中心（[ 3 D * –A]）三胞胎，显示双重磷光。3 [D •+ –A •– ]和[ 3D * –A]是通过两个系统间交叉机制并行形成的：自旋轨道电荷转移（SOCT）和超精细偶合（HFC），其溶剂依赖性支化比。溶剂在冷冻过程中驱动D–A排列，以适应增加的溶剂极性，产生非均质的基态种群分布，并具有溶剂依赖性的D–A交换相互作用，这在划分为SOCT和HFC机制中起着关键作用。在极地眼镜中，由于3 [D •+ –A •– ]中的解离后ET，出现了第三个磷光带，从而导致开环双自由基激发。
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