Tailoring of heteroleptic copper based photosensitizers and their photophysical characterization

充足和环境友好的能源供应是本世纪的一项重大挑战。一个有希望的选择是增加太阳能的使用，这需要设计高效、廉价和可持续的光敏剂来收集光。此外，合适的光敏剂应具有强的可见光吸收，长寿命的激发态，可逆的电化学行为和高的稳定性。到目前为止，分子光敏剂大多是基于稀有和贵重金属，如铱或钌，限制了它们的大规模应用。在这种方法中，基于地球上丰富的金属的配合物的使用是相当未开发的。要把这种不高尚的制度付诸实践，就必须改变。在这方面，光活性铜(I)配合物具有很大的潜力。因此，提出的项目涉及定制异电性Cu(I)光敏剂的开发，并详细研究其（三重态）激发态及其电荷转移过程。为此，将采用不同的设计策略，例如用异齿P^N配体交换经典的二膦配体或将二亚胺与二膦配体直接连接，以提高稳定性和吸收率。此外，将引入额外的电子存储部分，这允许影响氧化还原特性，以及光诱导电子转移的效率和时间常数。新设计的Cu(I)配合物将通过稳态以及时间分辨瞬态吸收和发射光谱进行系统研究，以阐明潜在的结构-性质关系，并了解激发态的性质。这将最终导致合成指南，例如配体的正确选择，取代基的类型和位置以及电子存储的类型。在迭代过程中，这些发现将直接用于进一步改进这些Cu(I)光敏剂。此外，这些异感铜(I)配合物将首次应用于光子上转换过程。因此，这些化合物将低能量光子转化为高能量光子的能力将得到澄清，从而允许在随后的反应中使用更大范围的光。总而言之，通过对新型光活性Cu(I)配合物的合成、结构和光谱表征以及应用的结合，本项目将使异效性铜光敏剂成为SPP 2102优先项目中有价值的一类物质。这最终将有助于增加利用和转换阳光作为一种有前途的清洁能源。

The sufficient and environmentally friendly supply of energy is a major challenge in this century. A promising option is given by the increased use of solar energy, which requires the design of efficient, inexpensive and sustainable photosensitizers for light harvesting. In addition, a suitable photosensitizer should possess a strong absorption in the visible, long-lived excited states, a reversible electrochemical behavior and a high stability.So far molecular photosensitizers are most often based on rare and precious metals, like iridium or ruthenium, limiting their large-scale application. The usage of complexes based on earth-abundant metals in this approach is rather unexplored. To bring such non-noble systems into practice that has to be changed. In this respect photoactive copper(I) complexes possess a great potential.Therefore, the proposed project deals with the development of tailored heteroleptic Cu(I) photosensitizers and the detailed investigation of their (triplet) excited states as well as of their charge-transfer processes. For this purpose different design strategies, e.g. the exchange of classic diphosphine ligands by heterobidentate P^N ligands or a direct connection of the diimine and the diphosphine ligand, will be applied to enhance stability and absorptivity. Furthermore, additional electron storage moieties will be introduced, which allow to affect the redox properties specifically as well as the efficiency and time constant of the photoinduced electron transfer.The newly designed Cu(I) complexes will be systematically studied by steady-state as well as time-resolved transient absorption and emission spectroscopy to elucidate the underlying structure-property relationships and to understand the nature of the excited states. This should ultimately result in synthesis guidelines, e.g. in instructions to the right choice of the ligands, the type and position of substituents and the kind of electron storage. Within an iterative process these findings will be used straight away to further improve these Cu(I) photosensitizers.Moreover, these heteroleptic Cu(I) complexes will be applied for photon upconversion processes for the first time. In consequence, the capability of these compounds to transform photons of low energy into high energy photons, which allows to use a broader range of the light in subsequent reactions, will be clarified.All in all, by the combination of synthesis, structural and spectroscopic characterization as well as application of novel photoactive Cu(I) complexes this project will establish heteroleptic copper photosensitizers as a valuable class of substances for the priority program SPP 2102. This will finally contribute to an increased utilization and conversion of sunlight as a promising and clean energy source.