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，在激素和色素的生物合成中起着重要的氧活化作用。尽管在生物无机模型复合物的设计中付出了巨大的努力，但对酚类底物的关键氧转移步骤以及由此产生的儿茶酚酸酯对醌的后续反应性仍然没有完全理解。在第一个资助期间，我们能够表征高保真功能酪氨酸酶模型。现在，我们的目标是通过密度泛函理论对催化循环的每一步进行详细的光谱分析。计划中的研究将联合收割机经典分析技术（低温紫外/维斯光谱法、催化衍生法、X射线结构分析）与可见光、紫外和真空紫外光谱范围内的非弹性光散射以及X射线吸收光谱法相结合。它们的利用允许反应中间体的表征，使反应过程的详细说明，从而提供真正的新见解酪氨酸酶。第二部分的工作是合成一种光活化的氧转移体系，并对其进行共振拉曼光谱和XAS光谱的研究。该系统的设计设想了在用合适的光源激发时的仿生羟基化反应性。在研究小组的第二阶段，我们将继续发展不同的样本分配和操作方法。我们的目标是建立几种技术，允许访问广泛的时间尺度内泵探测（FS）和泵探测流（高达S）实验的胍和双（吡唑基）甲烷为基础的模型配合物。作为输送系统，我们将应用SP1中开发的喷射和气溶胶技术以及Peltier冷却冷冻系统进行停止冷冻测量。对于电子转移的刺激，我们将使用共振和泵浦-探测拉曼测量。反应的基本动力学也将与时间分辨透射技术进行研究，并辅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。单独和组合，这些技术允许详细表征的结构和功能的胍和双（吡唑基）甲烷为基础的模型配合物内的仿生催化循环。

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.