Analysis of structures and reactions in isolated molecules and clusters after photo excitation by combined IR/UV spectroscopic methods

在这个项目中，我们将在分子束实验中用不同质量和不同同分异构体的选择性UV/IR光谱技术(最多四重共振法)对电子激发态和电子基态的光诱导反应进行结构分析。这些复杂的方法可以在分子水平上分析光物理过程；它们可以应用于孤立的物种和聚集体(例如，通过连续添加水分子而产生)。因此，可以确定环境对结构和反应活性的影响。详细的结构解释将通过与从头计算和密度泛函理论计算的比较得出。一个重要的方面是质子转移坐标的实验和理论分析。基于我们对激发态质子转移(ESPT)反应的研究，我们现在将分析电子激发后的双质子转移反应。根据理论预测，首次对光开关模型3-羟基吡啶甲酸进行了红外/紫外光谱分析。对ESPT反应的进一步分析将扩展到没有分子束条件下红外研究的超级光学酸。我们的分析使我们能够确定质子转移所需的溶剂分子的数量。可以识别可能的质子线或红外诱导的反应。此外，为了更好地描述电子激发态中的势能面，还将讨论有关电子激发后泛音光谱的进一步方法学发展。在另一种方法的发展中，红外引发的电子基态的质子转移和重排反应将用IR/UV探针方法进行分析。另一个重要的重点包括香豆素衍生物的结构和反应活性的分析。一方面是不同香豆素(杂二聚体)的自聚集和聚集，除了我们的前期工作外，到目前为止还没有在孤立的分子束条件下进行研究。关于这类物质的反应性，将研究基于香豆素的笼状化合物在光照后能够释放例如药物分子的情况。反应通道的分析将通过我们的质量和同分异构体选择、振动分辨方法来执行。因此，我们能够在分子水平上深入了解笼状化合物的光反应机理。关于合成，将建立与其他工作组合作的凝聚相理论和光谱学。

In this project photoinduced reactions in electronically excited states as well as in the electronic ground state will be structurally analysed in molecular beam experiments by different mass and isomer selective UV/IR spectroscopic techniques (up to quadruple resonance methods). These sophisticated methods allow an analysis of photophysical processes on a molecular level; they can be applied for isolated species as well as aggregates (e.g. generated by successive addition of water molecules). Thus the influence of an environment on structure and reactivity can be determined. A detailed structural interpretation will be drawn from a comparison with ab initio and DFT calculations.An important aspect is the experimental and theoretical analysis of proton transfer coordinates. Based on our investigations on ESPT (excited state proton transfer) reactions we will now analyse double proton transfer reactions after electronic excitation. According to theoretical predictions the first IR/UV analyses of the photo switch model 3-hydroxy-picolinic acid will be performed. Further analyses on ESPT reactions will be extended to super photo acids, for which no IR-investigations under molecular beam conditions exist. Our analysis enables us to determine the number of solvent molecules necessary for a proton transfer. Possible proton wires or IR-induced reactions can be identified. Beyond this, further methodical developments regarding the spectroscopy of overtones after electronic excitation will be addressed for a better description of the potential energy surface in electronically excited states. In another methodical development IR triggered proton transfers and rearrangement reactions in the electronic ground state will be analysed by an IR/UV probe method.A further important focus includes the analysis of the structure and reactivity of coumarin derivatives. One aspect is the self-aggregation as well as the aggregation of different coumarins (hetero dimers), for which (except for our preliminary work) no investigations under isolated molecular beam conditions have been performed so far. With regard to the reactivity of this substance class coumarin based caged compounds being able to release e.g. drug molecules after irradiation with light will be investigated. The analysis of reaction channels will be performed by our mass- and isomerselective, vibrationally resolved methods. Thus, we are able to gain insight into the mechanism of photoreactivity for caged compounds on a molecular level. With regard to synthesis, theory and spectroscopy in condensed phase cooperations with other working groups will be established.