Elementary Steps in Gold Photocatalysis

尽管取得了很大的进展，但涉及双核金（I）配合物或单核金（III）配合物的许多关键步骤仍然知之甚少。因此，对基元反应和关键中间体的详细了解对于概念性地设计新的合成路线至关重要。因此，在双核金配合物与碘取代的炔反应中形成自由的“炔基”仍然是非常值得怀疑的。因此，一个中心问题涉及这种“炔基自由基”衍生的产物和其他现有的反应性物种的起源。在这方面，金-炔基物质的形成可能是可行的。金催化的电子转移机制已经被提出用于双核金配合物以及金（III）配合物。在不吸收蓝色LED的光的双核络合物的情况下，需要碱以形成金基聚集体，从而可以避免使用高能UVA光。这种中间体的性质仍需澄清。为此，需要结合实验/计算方法。实验机制研究包括原位光谱，化学计量控制实验，荧光猝灭实验和关键中间体的分离。在这方面，关键中间体的分离可以通过由理论方法指导的底物或金属络合物的修饰来实现。与双核金配合物的光催化行为的理论描述相比，它们的实验应用是罕见的，将首先开发一个全面的计算协议。这不仅使调查的能量的反应机制，但也计算激发态的性质。这将被用于识别的光敏中间体，并为后续的双核Au的催化步骤的彻底评价。在此检查的催化循环的关键功能将是预测的光谱特征的可疑中间体的实验验证，以及计算的能量分布的机制。此外，该协议将有助于系统的理论阐明的差异之间的SET和EnT机制的双核金双。

Despite great progress, many key steps in photocatalysis involving dinuclear gold(I) complexes or mononuclear gold(III) complexes remain poorly understood. A detailed understanding of elementary reactions and key intermediates is therefore crucial to conceptually design new synthetic routes. As such, the formation of free “alkynyl radicals” in the reaction of dinuclear gold complexes with iodo-substituted alkynes remains highly doubtable. Therefore, a central question involves the origin of such “alkynyl radical”-derived products and other present reactive species. In this regard the formation of gold-alkynyl species could be feasible. Thus, the exact mechanistic steps need to be elucidated.Gold-catalyzed electron transfer mechanisms were already proposed for dinuclear gold complexes as well as gold(III) complexes. In case of the dinuclear complex which does not absorb the light of blue LEDs, a base is necessary in order to form a gold-base aggregate so that the use of highly energetic UVA light can be avoided. The nature of this intermediate still needs to be clarified. For this, a combined experimental/computational approach is required. Experimental mechanistic studies consist of in situ spectroscopy, stoichiometric control experiments, fluorescence quenching experiments and isolation of key intermediates. In this regard, isolation of key intermediates could be achieved by modification of the substrates or metal complex guided by a theoretical approach. With a theoretical description of the photocatalytic behavior of dinuclear gold complexes being rare in comparison to their experimental application, a comprehensive computational protocol will first be developed. This not only enables the investigation of the energetics of such reaction mechanisms but also the calculation of excited state properties. This will be employed for the identification of photoactive intermediates and for the thorough evaluation of the subsequent catalytic steps within dinuclear Au-photocatalysis. Key features within this examination of the catalytic cycle will be the prediction of spectroscopic signatures of suspected intermediates for experimental verification as well as the computation of the energetic profile of the mechanism. Furthermore the protocol will be instrumental for the systematic theoretical elucidation of differences between SET and EnT mechanisms in dinuclear gold photocatalysis.