Hua Shao-An, Cattaneo Mauricio, Oelschlegel Manuel, Heindl Moritz, Schmid Lucius, Dechert Sebastian, Wenger Oliver S, Siewert Inke, González Leticia, Meyer Franc
University of Göttingen, Institute of Inorganic Chemistry, Tammannstrasse 4, D-37077 Göttingen, Germany.
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, A-1090 Vienna, Austria.
Inorg Chem. 2020 Apr 6;59(7):4972-4984. doi: 10.1021/acs.inorgchem.0c00220. Epub 2020 Mar 6.
The development of new solar-to-fuel scenarios is of great importance, but the construction of molecular systems that convert sunlight into chemical energy represents a challenge. One specific issue is that the molecular systems have to be able to accumulate redox equivalents to mediate the photodriven transformation of relevant small molecules, which mostly involves the orchestrated transfer of multiple electrons and protons. Disulfide/dithiol interconversions are prominent 2e/2H couples and can play an important role for redox control and charge storage. With this background in mind, a new photosensitizer [Ru(bpy)(bpy)] () equipped with a disulfide functionalized bpy ligand (bpy, bpy = 2,2'-bipyridine) was synthesized and has been comprehensively studied, including structural characterization by X-ray diffraction. In-depth electrochemical studies show that the bpy ligand in can be reduced twice at moderate potentials (around -1.1 V vs Fc), and simulation of the cyclic voltammetry (CV) traces revealed potential inversion ( > ) and allowed to derive kinetic parameters for the sequential electron-transfer processes. However, reduction at room temperature also triggers the ejection of one sulfur atom from , leading to the formation of Ru(bpy)(bpy). This chemical reaction can be suppressed by decreasing the temperature from 298 to 248 K. Compared to the archetypical photosensitizer [Ru(bpy)], features an additional low energy optical excitation in the MLCT region, originating from charge transfer from the metal center to the bpy ligand (aka MSCT) according to time-dependent density functional theory (TD-DFT) calculations. Analysis of the excited states of on the basis of ground-state Wigner sampling and using charge-transfer descriptors has shown that bpy modification with a peripheral disulfide moiety leads to an energy splitting between charge-transfer excitations to the bpy and the bpy ligands, offering the possibility of selective charge transfer from the metal to either type of ligands. Compound is photostable and shows an emission from a MLCT state in deoxygenated acetonitrile with a lifetime of 109 ns. This work demonstrates a rationally designed system that enables future studies of photoinduced multielectron, multiproton PCET chemistry.
开发新的太阳能转化为燃料的方案非常重要，但构建将太阳光转化为化学能的分子系统是一项挑战。一个具体问题是，分子系统必须能够积累氧化还原当量，以介导相关小分子的光驱动转化，这主要涉及多个电子和质子的协同转移。二硫键/二硫醇的相互转化是突出的2e/2H对，可在氧化还原控制和电荷存储中发挥重要作用。基于此背景，合成了一种配备二硫键功能化bpy配体（bpy，bpy = 2,2'-联吡啶）的新型光敏剂[Ru(bpy)(bpy)]（），并对其进行了全面研究，包括通过X射线衍射进行结构表征。深入的电化学研究表明，中的bpy配体可在中等电位（相对于Fc约为-1.1 V）下被还原两次，循环伏安法（CV）曲线的模拟揭示了电位反转（>），并允许推导连续电子转移过程的动力学参数。然而，室温下的还原也会触发一个硫原子从中逸出，导致[Ru(bpy)(bpy)]（）的形成。通过将温度从298 K降低到248 K，可以抑制这种化学反应。与典型的光敏剂[Ru(bpy)]相比，根据含时密度泛函理论（TD-DFT）计算，在MLCT区域具有额外的低能量光学激发，源于从金属中心到bpy配体的电荷转移（又名MSCT）。基于基态维格纳采样并使用电荷转移描述符对的激发态进行分析表明，用外围二硫键部分修饰bpy会导致向bpy和bpy配体的电荷转移激发之间的能量分裂，提供了从金属向任一种配体选择性电荷转移的可能性。化合物在脱氧乙腈中是光稳定的，并显示出从MLCT态发射，寿命为109 ns。这项工作展示了一个经过合理设计的系统，能够用于未来光诱导多电子、多质子PCET化学的研究。
