Institute of Physical Chemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany.
Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstraße 12, 53115, Bonn, Germany.
Chemistry. 2021 Feb 5;27(8):2683-2691. doi: 10.1002/chem.202002805. Epub 2020 Dec 1.
Photogenerated multi-spin systems hold great promise for a range of technological applications in various fields, including molecular spintronics and artificial photosynthesis. However, the further development of these applications, via targeted design of materials with specific magnetic properties, currently still suffers from a lack of understanding of the factors influencing the underlying excited state dynamics and mechanisms on a molecular level. In particular, systematic studies, making use of different techniques to obtain complementary information, are largely missing. This work investigates the photophysics and magnetic properties of a series of three covalently-linked porphyrin-trityl compounds, bridged by a phenyl spacer. By combining the results from femtosecond transient absorption and electron paramagnetic resonance spectroscopies, we determine the efficiencies of the competing excited state reaction pathways and characterise the magnetic properties of the individual spin states, formed by the interaction between the chromophore triplet and the stable radical. The differences observed for the three investigated compounds are rationalised in the context of available theoretical models and the implications of the results of this study for the design of a molecular system with an improved intersystem crossing efficiency are discussed.
光致多自旋体系在分子自旋电子学和人工光合作用等多个领域的一系列技术应用中具有广阔的应用前景。然而，通过有针对性地设计具有特定磁性能的材料来进一步发展这些应用，目前仍然缺乏对影响分子水平下基础激发态动力学和机制的因素的理解。特别是，系统的研究，利用不同的技术来获取互补的信息，在很大程度上是缺失的。本工作研究了一系列通过苯环间隔基连接的三个共价键联卟啉-三苯甲基化合物的光物理和磁性质。通过结合飞秒瞬态吸收和电子顺磁共振光谱的结果，我们确定了竞争的激发态反应途径的效率，并通过发色团三重态和稳定自由基之间的相互作用来表征单个自旋态的磁性质。在可用的理论模型的背景下，对三种研究化合物的差异进行了合理化解释，并讨论了本研究结果对设计具有改进系间窜越效率的分子体系的意义。
