A Spectroscopic Investigation of Luminescent Cr(III) Complexes

光化学是利用可见光或紫外光作为催化剂，促进具有不同化学性质的新化学物质的形成，它在分子合成、治疗诊断和发光二极管等新技术应用中日益重要。光能的吸收通常涉及顺磁激发态或载流子的产生，这些载流子在电子转移事件中起着至关重要的作用，显示出与基态过程显著不同的化学性质。然而，由于它们的寿命短得令人难以置信，这些物种经常逃避检测。在这个项目中，我们将应用TR-EPR方法来获得动力学、分子剖面和结构模型的精确分辨率，这些模型在稳态条件下由于快速弛豫过程而无法获得。TR-EPR将提供优化高效光合系统和设备所需的电荷传输机制的基础知识。本研究与EPSRC“光子材料战略优先”及相关能源应用材料主题直接相关。该项目将提供高级光谱学和化学合成方面的博士培训方案，在一个经验丰富的项目团队之间进行协作。初始研究活动的两个领域将集中于(i) Ir（III）配合物的光子上转换和（ii）染料敏化半导体太阳能电池的可持续敏化剂。这两个研究领域都将在项目时间框架内取得重大进展。光子上转换作为一种提高光收集过程、光氧化还原催化和生物成像剂效率的手段受到了极大的关注。Co-I最近利用新型的基于Ir（III）的供体：受体系统，通过三重-三重上转换，展示了领先的转化效率。欧元。J. (2018), DOI:10.1002/chem.201801007)。TR-EPR非常适合于光激发系统的自旋相互作用（例如瞬态有机三重态，自旋轨道耦合参数）的完全解绕，其结果指导合理设计供体：受体对以获得最大的上转换和选择性发射波长。金属氧化物半导体的光激发产生可用于表面氧化还原过程和电薄膜器件的载流子。PI最近在该领域提供了独特的见解，利用EPR来识别光辐射过程中固有/掺杂氧化态的变化。将探索铜基敏化剂的开发（由Co-I），以最大限度地提高光激发谱并优化电荷转移过程，为未来的太阳能电池提供可持续的低成本路线。

Photochemistry, in which visible or ultraviolet light is used as a catalyst to promote the formation of new chemical species with distinct chemical properties, is of growing importance for molecular synthesis, therapeutic diagnostics and new technological applications such as light emitting diodes. Absorption of light energy frequently involves the creation of paramagnetic excited states or charge carriers that play vital roles in electron transfer events, displaying significantly different chemistry to ground state processes. However, these species often evade detection due to their incredibly short lifetimes. In this project we will apply TR-EPR methods to yield accurate resolution of kinetics, molecular profiles, and structural models which cannot be accessed under steady-state conditions due to rapid relaxation processes. TR-EPR will provide fundamental knowledge of charge transport mechanisms required for the optimization of efficient photosynthetic systems and devices. This research is directly relevant to EPSRC Strategic Priority for Photonic Materials and the related Materials for Energy Applications themes.This project will provide a Ph.D. training regimen in advanced spectroscopy and chemical synthesis, in a collaborative nature between an experienced project team. Two areas of initial research activity will focus on (i) Photon Upconversion by Ir(III) Complexes, and (ii) Sustainable sensitizers for dye-sensitized semiconductor solar cells. Both research areas will yield significant advances within the project timeframe.Photon upconversion has received significant attention as a means of increasing the efficacy of light harvesting processes, photoredox catalysis and for bioimaging agents. The Co-I has recently demonstrated leading conversion efficiencies using novel Ir(III)-based donor:acceptor systems through triplet-triplet upconversion (Chem. Eur. J. (2018), DOI:10.1002/chem.201801007). TR-EPR is ideally suited to fully disentangle the spin interactions of the photoexcited system (e.g. transient organic triplets, spin-orbit coupling parameters), results guiding rational design of donor:acceptor pairs for maximum upconversion and selective emission wavelengths. Photoexcitation of metal oxide semiconductors creates charge carriers that can be utilised in surface redox processes and in electrical thin-film devices. The PI has recently provided unique insights into this area by utilising EPR to identify intrinsic/dopant oxidation state changes during photoirradiation. The development of copper-based sensitizers (by the Co-I) will be explored to maximise photoexcitation profiles and optimise charge-transfer processes providing a sustainable, low-cost route towards solar cells of the future.