Dispersion interactions in isolated molecules and molecular aggregates analyzed by IR/UV and Raman/UV double resonance spectroscopy

通过红外/紫外和拉曼/紫外双共振光谱分析孤立分子和分子聚集体中的分散相互作用

• 批准号: 271505332
• 负责人: Privatdozent Dr. Christoph Riehn, since 5/2021
• 金额: --
• 依托单位: Fachrichtung Physikalische und Theoretische Chemie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/271505332?language=en
• 关键词: Dispersion; interactions; isolated; molecules; molecular

In this project we analyze a variety of molecular systems with competing structural arrangements in which London dispersion forces are important for the energetic preferences. Furthermore, dimers that are only stable if dispersion interactions are strong enough are considered, like substituted hexaphenyl ethane dimers with e.g. unusually short distances between H atoms. Both the influence and quantity of dispersion forces will be investigated with the help of spectroscopic techniques in molecular beam experiments yielding vibrational frequencies and electronic energies in comparison to quantum chemical methods. One set of systems to be investigated are ether–alcohol clusters in which the alcohol molecule can form a hydrogen bond to the ether oxygen or to a pi cloud and where a varying alcohol side-chain is able to control the docking preference due to changed amounts of dispersion interactions. Alternatively, an attached aromatic alcohol molecule can interact with different alkyl side chains, driven by the strength of dispersion interactions. A further class of investigated clusters are aggregates of asymmetric ketones (including protected amino acids) with alcohol molecules. Here, different orientations of the side-chains of the alcohol molecule with respect to the two lone pairs of the carbonyl oxygen atom are possible. All analyses, both for the ether–alcohol and ketone–alcohol clusters, describe a critical balance between nearly isoenergetic structures, i.e. difficult cases for theoretical predictions are presented, since the uncertainty with respect to energetic differences can be in the region of the difference of zero point energies. We focus our molecular beam investigations on the electronic ground state of neutral and partly ionic clusters, but also on the excited state of the neutral species by applying a variety of combined mass- and isomer-selective IR/UV techniques as well as stimulated Raman/UV techniques. Furthermore a new combined IR/Raman/UV variant which is important for isomer-selective measurements will be developed and applied. Our experimental investigations will be performed in close cooperation with other working groups in the field of complementary spectroscopic methods, theory, and synthesis. The synthetic groups also provide us with specifically deuterated or fluorinated compounds. It is a general aim to offer a variety of experimental results in comparison with theoretical predictions. By this an improvement and development of (new) theoretical methods can be achieved in order to get a better quantification of London dispersion, including especially the analysis of electronically excited states.

在这个项目中，我们分析了具有竞争结构排列的各种分子系统，其中伦敦色散力对于能量偏好很重要此外，只有当色散相互作用足够强时才考虑稳定的二聚体，例如取代的六苯基乙烷二聚体。 H原子之间的短距离。将借助分子束实验中的光谱技术来研究色散力的影响和数量，与一组量子化学方法相比，产生振动频率和电子能量。要研究的系统是醚-醇簇，其中醇分子可以与醚氧或π云形成氢键，并且由于分散相互作用量的变化，不同的醇侧链能够控制对接偏好或者，在分散相互作用强度的驱动下，附着的芳香醇分子可以与不同的烷基侧链相互作用。这里，不同的不对称酮（包括受保护的氨基酸）聚集体。醇分子的侧链相对于羰基氧原子的两个孤对的取向是可能的，对于醚-醇和酮-醇簇来说，所有分析都描述了近等能结构之间的关键平衡，即提出了理论预测的困难情况，因为能量差异的不确定性可能位于零点能量差异的区域，我们将分子束研究的重点放在中性和部分离子的电子基态上。簇，而且还通过应用各种组合的质量和异构体选择性红外/紫外技术以及受激拉曼/紫外技术来研究中性物质的激发态。此外，新的组合红外/拉曼/紫外变体也很重要。我们将与互补光谱方法、理论和合成领域的其他工作组密切合作，开发和应用异构体选择性测量的方法。总体目标是提供与理论预测相比的各种实验结果，从而可以实现（新）理论方法的改进和发展，以便更好地量化伦敦色散，尤其是伦敦色散。电子激发态分析。