Light-induced electron transfer/phase migration of a redox mediator for photocatalytic C?C coupling in a biphasic solution
Light-induced electron transfer/phase migration of a redox mediator for photocatalytic C?C coupling in a biphasic solution
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用于双相溶液中光催化 C?C 耦合的氧化还原介体的光诱导电子转移/相迁移
DOI：
10.1039/d2dt01334g
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发表时间：
2022
影响因子：
4
通讯作者：
Nakada Akinobu
中科院分区：
文献类型：
--
作者：
Itagaki Ren;Takizawa Shin-ya;Chang Ho-Chol;Nakada Akinobu
产生增值化学品的光催化分子转化引起了人们的极大兴趣。为了实现高效的光催化反应，构建能够有效电荷分离的系统具有挑战性，因此同样重要。在这里，我们证明了具有二茂铁/二茂铁（Fc+/Fc）氧化还原电对的双相溶液系统的合理构建能够通过液-液界面的空间电荷分离实现高效的光催化。在单相系统中，将含有 Ru(II) 或 Ir(III) 基光敏剂、Fc 和苄基溴 (Bn-Br) 的 1,2-二氯乙烷 (DCE) 溶液暴露在可见光照射下未能生成任何产物。然而，H2O/DCE 双相溶液中的光解作用（其中化合物最初分布在 DCE 相中）促进了使用 Fc 作为电子供体将 Bn-Br 还原偶联到二苄基 (Bn2)。这项研究的关键结果是，DCE 相中 Fc 光氧化产生的 Fc+ 迁移到水相，因为与 Fc 相比，其分配系数发生了巨大变化。介体的这种液-液相迁移对于促进 DCE 相中 Bn-Br 的还原至关重要，因为它抑制了反向电荷复合。阴离子的共存可以根据其亲水性进一步改变Fc+相迁移的驱动力；通过向双相溶液中添加 NBu4+Br− 形成 Bn2，获得了最佳光催化活性，周转频率为 79.5 h−1，量子效率为 0.2%。这项研究展示了一种通过抑制电荷复合来整流电子转移以实现高效光催化的潜在方法。
Photocatalytic molecular conversions that lead to value-added chemicals are of considerable interest. To achieve highly efficient photocatalytic reactions, it is equally important as it is challenging to construct systems that enable effective charge separation. Here, we demonstrate that the rational construction of a biphasic solution system with a ferrocenium/ferrocene (Fc+/Fc) redox couple enables efficient photocatalysis by spatial charge separation using the liquid–liquid interface. In a single-phase system, exposure of a 1,2-dichloroethane (DCE) solution containing a Ru(II)- or Ir(III)-based photosensitizer, Fc, and benzyl bromide (Bn-Br) to visible-light irradiation failed to generate any product. However, the photolysis in a H2O/DCE biphasic solution, where the compounds are initially distributed in the DCE phase, facilitated the reductive coupling of Bn-Br to dibenzyl (Bn2) using Fc as an electron donor. The key result of this study is that Fc+, generated by photooxidation of Fc in the DCE phase, migrates to the aqueous phase due to the drastic change in its partition coefficient compared to that of Fc. This liquid–liquid phase migration of the mediator is essential for facilitating the reduction of Bn-Br in the DCE phase as it suppresses backward charge recombination. The co-existence of anions can further modify the driving force of phase migration of Fc+ depending on their hydrophilicity; the best photocatalytic activity was obtained with a turnover frequency of 79.5 h−1 and a quantum efficiency of 0.2% for the formation of Bn2 by adding NBu4+Br− to the biphasic solution. This study showcases a potential approach for rectifying electron transfer with suppressed charge recombination to achieve efficient photocatalysis.