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

在该项目中，将在分子束实验中通过不同的质量和异构体选择性UV/IR光谱技术（最多四重共振方法）对电子激发态和电子基态的光致反应进行结构分析。这些复杂的方法允许在分子水平上分析生物物理过程;它们可以应用于孤立的物种以及聚集体（例如通过连续添加水分子产生的）。因此，可以确定环境对结构和反应性的影响。通过与从头算和密度泛函理论计算的比较，我们将得到一个详细的结构解释，其中一个重要方面是质子转移坐标的实验和理论分析。基于我们对ESPT（激发态质子转移）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，将进行光开关模型3-羟基-吡啶甲酸的第一IR/UV分析。对ESPT反应的进一步分析将扩展到超级光酸，在分子束条件下不存在IR研究。我们的分析使我们能够确定质子转移所需的溶剂分子数量。可以识别可能的质子线或IR诱导的反应。除此之外，关于电子激发后的泛音光谱学的进一步方法发展将得到解决，以更好地描述电子激发态的势能面。在另一个方法发展中，将通过IR/UV探针方法分析电子基态的IR引发的质子转移和重排反应。更重要的焦点包括香豆素衍生物的结构和反应性的分析。一个方面是自聚集以及聚集不同的香豆素（异源二聚体），其中（除了我们的初步工作）没有调查隔离分子束条件下已进行到目前为止。关于该物质类的反应性，将研究基于香豆素的笼状化合物在用光照射后能够释放例如药物分子。反应通道的分析将通过我们的质量和异构体选择性，振动分辨方法进行。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性机制。关于合成，理论和光谱在凝聚相合作与其他工作组将建立。

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.