Light induced charge transfer processes in bis-oxo and peroxo dicopper complexes for biomimetic hydroxylation

酪氨酸酶是一种普遍存在的金属酶，在氧气活化激素和色素的生物合成中起着核心作用。尽管在生物无机模型化合物的设计上做了很大的努力，但关键的氧向酚类底物转移的步骤以及由此产生的儿茶酚对苯二酚的反应性仍然不完全清楚。在第一个资助期，我们能够描述一个高保真的功能性酪氨酸酶模型。现在，我们的目标是对催化循环的每个步骤进行详细的光谱分析，并辅之以密度泛函理论。计划中的研究将经典分析技术(低温UV/Vis光谱、催化衍生方法、X射线结构分析)与可见光、紫外线和真空紫外线光谱范围内的非弹性光散射以及X射线吸收光谱相结合。利用它们可以对反应中间体进行表征，从而能够详细阐明反应过程，从而提供对酪氨酸酶的真正新的见解。同时，我们考察了底物的范围和催化剂的性能。项目的第二部分旨在合成一种光活化的氧转移体系，并对其进行了共振拉曼光谱和X射线吸收光谱的研究。该系统的设计设想了在合适的光源下激发时的仿生羟基化反应。在研究组的第二阶段，我们将继续开发不同的样本分配和处理方法。我们的目标是建立几种技术，以允许访问广泛的时间范围内的泵浦-探测(FS)和泵浦-探测-流动(最高S)实验的胍和双(吡唑基)甲烷模型化合物。作为输送系统，我们将应用SP1开发的喷射和气溶胶技术，以及用于停止冻结测量的珀尔蒂埃冷却冷冻系统。对于电子转移的模拟，我们将使用共振和泵浦探测拉曼测量。这些反应的基本动力学也将用时间分辨传输技术进行研究，并辅之以时间分辨拉曼测量。我们的技术能力得到了稳态和时间分辨X射线吸收精细结构(XAFS)测量的补充。这些技术单独或结合在一起，可以在仿生催化循环中详细表征基于胍和双(吡唑基)甲烷的模型化合物的结构和功能。

Tyrosinase is a ubiquitous metalloenzyme which plays the central role in dioxygen activation for the biosynthesis of hormones and pigments. Despite great efforts in the design of bioinorganic model complexes, the crucial oxygen-transferring step towards phenolic substrates as well as the subsequent reactivity of the resulting catecholates to quinones is still not fully understood. During the first funding period, we were able to characterize a high fidelity functional tyrosinase model. Now, we target a detailed spectroscopic analysis of each step of the catalytic cycle complemented by density functional theory. The planned studies combine classical analytical techniques (low-temperature UV/Vis spectroscopy, catalysis-derived methods, X-ray structure analysis) with inelastic light scattering in the visible, ultra-violet, and vacuum ultra-violet spectral range as well as X-ray absorption spectroscopy. Their utilization allows for the characterization of reaction intermediates enabling the detailed elucidation of the reaction progress and thus delivering truly new insights into tyrosinase. Concomitantly, we investigate the substrate scope and enhance the catalyst performance.The second part of the project aims at the synthesis of a photoactivatable oxygen-transferring system which is subject to combined resonance Raman and XAS studies. The design of this system envisions a biomimetic hydroxylation reactivity upon excitation with suited light sources. In the second period of the Research Group we will continue the development of different methods for sample allocation and manipulation. Our aim is to establish several techniques that allow to access a broad range of timescales within pump-probe (fs) and pump-probe-flow (up to s) experiments of guanidine- and bis(pyrazolyl)methane-based model complexes. As delivery systems we will apply the jet and aerosol technology developed in SP1 as well as Peltier-cooled cryo-systems for stop freeze measurements. For the stimulation of electron transfer, we will use resonance and pump-probe Raman measurements. The basic kinetics of the reactions will also be investigated with time-resolved transmission techniques and complemented by time resolved Raman measurements. Our technical capabilities are complemented by steady state and time resolved X-ray absorption fine structure (XAFS) measurements. Alone and in combination, these techniques allow a detailed characterization of the structure and function of guanidine- and bis(pyrazolyl)methane-based model complexes within the biomimetic catalytic cycle.