Electronic structure of protonated aromatic and chiral molecules

该项目旨在对气相中分离的大小选择性质子化芳族分子及其簇进行激光光谱、质谱和量子化学表征，以确定其基态和激发电子态的几何和电子结构。目标分子是从苯到晕苯的质子化（多环）芳烃分子，以及具有非极性和极性配体（稀有气体原子、氮、水）的简单衍生物和簇，以模拟疏水和亲水溶剂化。所考虑的分子在有机化学、燃烧、生物化学和天体化学中具有基本的相关性。质子化对电子结构和几何结构有巨大的影响，因为它降低了芳香π电子系统的对称性和芳香性，并产生了低位电荷转移态。因此，质子化在很大程度上改变了这些芳香族分子的光化学和光物理，这在很大程度上是未经探索的实验和理论。此外，与溶剂分子的相互作用急剧变化后质子化和电子激发，和一个特别的焦点将是质子转移到/从溶剂中的微水化集群。要解决的基本问题包括能量，结构，电荷分布，分子轨道，质子化位点和质子亲和力，弛豫和碎裂机制，以及质子化，电子激发，微溶剂化和取代的功能基团的影响。光谱和量子化学结果的分析将提供这些基本物种在分子水平上的物理和化学性质的详细理解。 此外，我们将这些研究沿着一条新的研究路线延伸到质子化手性分子及其相互作用。手性和手性识别在生命和材料科学的许多领域中起着重要作用，其中许多现象在分子水平上还没有被理解。虽然在带电配合物的相互作用和手性歧视是强大的，很少有光谱信息是手性离子配合物。为此，我们将探讨手性离子复合物中的相互作用，通过考虑（i）1-氨基-2-茚满醇（用于不对称合成）和（ii）谷氨酸（蛋白质氨基酸和神经递质）的原型质子化（芳香族）复合物。基本的手性特定的问题，要解决的手性歧视的强度质子化的影响，个人的力量（排斥，静电，感应，分散）的重要性，极性和非极性溶剂化的影响，与提供一个分子水平的理解在带电的手性复合物中的分子间相互作用和手性歧视的最终目标。

This project aims at the laser spectroscopic, mass spectrometric, and quantum chemical characterization of size-selected protonated aromatic molecules and their clusters isolated in the gas phase, to determine their geometric and electronic structure in the ground and excited electronic states. Target molecules are protonated (polycyclic) aromatic hydrocarbon molecules ranging from benzene to coronene, as well as simple derivatives and clusters with nonpolar and polar ligands (rare gas atoms, nitrogen, water) to mimic both hydrophobic and hydrophilic solvation. The considered molecules are of fundamental relevance in organic chemistry, combustion, biochemistry, and astrochemistry. Protonation has a huge impact on the electronic and geometric structure, because it reduces the symmetry and aromaticity of the aromatic pi-electron system and generates low-lying charge-transfer states. Hence, protonation largely changes the photochemistry and photophysics of these aromatic molecules, which are largely unexplored both experimentally and theoretically. In addition, the interaction with solvent molecules changes drastically upon protonation and electronic excitation, and a particular focus will be on proton transfer to/from solvent in microhydrated clusters. Fundamental questions to be addressed include the energy, structure, charge distribution, molecular orbitals, protonation site and proton affinity, relaxation and fragmentation mechanisms, as well as the effects of protonation, electronic excitation, microsolvation, and substitution of functional groups. The analysis of the spectroscopic and quantum chemical results will provide a detailed understanding of the photophysical and chemical properties of these fundamental species at the molecular level. In addition, we extend these studies along a new research line toward protonated chiral molecules and their interactions. Chirality and chiral discrimination play a fundamental role in a plethora of areas in life and materials sciences, and many of these phenomena are not understood at the molecular level. Although in charged complexes the interactions and resulting chiral discrimination are strong, little spectroscopic information is available for chiral ionic complexes. To this end, we will explore interactions in chiral ionic complexes by considering prototypical protonated (aromatic) complexes of (i) 1-amino-2-indanol (used in asymmetric synthesis) and (ii) glutamic acid (a proteinogenic amino acid and neurotransmitter). Fundamental chirality-specific questions to be addressed include the effects of protonation on the strength of chiral discrimination, the importance of the individual forces (repulsion, electrostatic, induction, dispersion), and the effects of polar and nonpolar solvation, with the ultimate goal of providing a molecular-level understanding of the intermolecular interactions and chiral discrimination in charged chiral complexes.