Exploiting the disulfide/dithiol switch in photoinduced proton coupled electron transfer reactions

与可持续能源方案相关的小分子转化，特别是太阳能燃料的产生，通常需要多个电子和质子的转移。因此，介导大多数惰性分子的这些具有挑战性的转化的催化剂必须协调复杂的多电子、多质子转移到/从底物，即质子耦合电子转移（PCET）事件，其也广泛存在于生物系统中。这些过程可以通过质子转移接着电子转移（PT-ET）或反之亦然（ET-PT）顺序进行，或者电子和质子可以以协同方式转移（CPET）以避免任何具有潜在高能量的带电中间体。由于其固有的非平衡性质发生时，从光激发态，光驱动的PCET方案是特别复杂的，并没有得到很好的理解。然而，理解和控制多个光触发的电荷转移过程的动力学将最终对改善太阳光到燃料的转化以及太阳能燃料中任何所需的能量存储至关重要。这个基础研究项目的目标是阐明在光诱导的PCET过程中的事件序列，使用新型的光激发金属络合物，在配体外围装饰有二硫化物/二硫醇开关。所提出的化学方法利用了二硫化物/二硫醇相互转化的2 e −/2 H+性质，以及二硫化物部分第一次还原后经常发生的潜在转化。在第一个资助期取得的进展的基础上，该项目的关键问题涉及精心设计的分子和超分子系统，包括ET，PT和S-S键断裂的光激发后的单个化学步骤的编排。这些问题是由一个跨学科的项目团队，并在与优先计划的几个研究小组密切合作，使用一套实验和计算方法来解决。的概念指导方针，和最终的目标，是触发第二个ET事件，可能耦合到PT，以下的初始激发态PCET过程。这将为单次光激发引发的多电子/多质子化学开辟一条新的途径。

The transformation of small molecules relevant for sustainable energy scenarios, specifically the generation of solar fuels, usually requires the transfer of multiple electrons and protons. Catalysts mediating these challenging transformations of mostly inert molecules thus have to orchestrate the complex multielectron, multiproton transfer to/from the substrate, viz. the proton-coupled electron transfer (PCET) events that are also widespread in biological systems. These processes may proceed sequentially via proton transfer followed by electron transfer (PT-ET), or vice versa (ET-PT), or the electron and proton may be transferred in a concerted fashion (CPET) to avoid any charged intermediates of potentially high energy. Because of their inherent nonequilibrium nature when occurring from photoexcited states, PCET scenarios driven by light are particularly complex and not well understood. However, understanding and controlling the dynamics of multiple light-triggered charge transfer processes will ultimately be crucial for improved sunlight to fuel conversion and for any desired energy storage in solar fuels. This fundamental research project targets the elucidation of the sequence of events during photoinduced PCET processes using novel photoexcitable metal complexes that are decorated with a disulfide/dithiol switch in the ligand periphery. The proposed chemistry capitalizes on the 2e−/2H+ nature of the disulfide/dithiol interconversion and on the potential inversion that often occurs after the first reduction of a disulfide moiety. Building upon the progress achieved during the first funding period, key questions of this project concern the choreography of the individual chemical steps following photoexcitation of well-designed molecular and supramolecular systems, including ET, PT and the rupture of the S-S bond. These questions are addressed by an interdisciplinary project team and in close collaborations with several research groups of the priority program, using a suite of experimental and computational methods. The conceptual guideline, and the ultimate goal, is the triggering of a second ET event, potentially coupled to PT, following the initial excited state PCET process. This will open a promising entry towards multielectron/multiproton chemistry initiated by single photoexcitation event.