Intramolecular dispersive interactions in the gas phase: experimental reference data and comparison with solid state and theory

我们的项目重点是应用气体电子衍射（GED）和其他方法来探索一系列具有分子内色散相互作用的自由分子的精确几何结构。将得到的自由气相分子的结果与单晶x射线衍射（XRD）在固态下得到的数据进行比较。这种不同相的研究将阐明分子间固态效应是否以及在多大程度上改变分子结构，以及色散相互作用的发生和强度。在更大、更复杂的系统上的大多数实验数据都是由固态方法得到的，但基本的相互作用最好用气相技术来研究。因此，可比性的问题是显而易见的。量子化学（QC）方法的发展也取得了巨大进展，用于描述越来越大的系统，包括对色散的彻底处理。然而，这样的计算通常适用于单分子，这与固态的结果又有所不同。将自由分子的实验数据与一系列最先进的QC计算进行比较，将有助于评估这种理论近似的质量。利用一组来自气相和固态方法以及QC的数据，我们将能够研究色散相互作用的方法或相依赖性。在第一个项目阶段，我们已经证明了我们的方法确实提供了关于分子内分散相互作用的发生和强度的有价值的结构和热化学信息。研究对象源于自身的准备工作（如C6H5/C6F5、Cu··Cu或Hg··Hg的相互作用）和与其他SPP基团（如大二聚体中的烷基/烷基）的协同作用。在某些情况下，我们发现气相实验与最高级别的QC计算之间存在严重差异，而在其他情况下，与某些QC方法非常吻合。我们还建立了用于合成挥发性双核金配合物的新配体体系。通过这种方式，我们学会了产生一系列新的分子，以研究某些类型的分散主导的相互作用的孤立形式。在第二个资助期，我们将利用这些知识，加深我们对分子内弥散相互作用的理解，并生产具有挑战性的新对象和实验数据，作为弥散校正QC方法的参考。我们还旨在了解某些方法对某些类型的化合物的失败。要研究的各种类型的分子内相互作用包括：a)碳氢化合物和有机硅烷中的σ∙∙∙∙∙相互作用，b)芳烯π∙∙∙π相互作用，c) σ-孔相互作用（卤素和硫键），d) d10∙∙∙d10（例如Au∙∙Au， Hg∙Hg）和d10∙∙d10（例如Au∙∙Au）。我们还将为SPP中至少四个其他组进行GED结构确定。

Our project focusses on applying gas electron diffraction (GED) and other methods to explore the precise geometrical structure of a range of free molecules with intramolecular dispersion interactions. The results obtained for free gas-phase molecules will be compared with data obtained in the solid state by single crystal X-ray diffraction (XRD). Such studies in different phases will clarify whether and to what extent intermolecular solid-state effects change molecular structures as well as the occurrence and strengths of dispersion interactions. Most of the experimental data on larger, more complicated systems are derived from solid-state methods, but the fundamental interactions are preferably studied by gas-phase techniques. The question of comparability is thus obvious. There is also enormous progress in quantum-chemical (QC) method development for describing increasingly larger systems including a thorough treatment of dispersion. However, such calculations are usually applied to single molecules – again different from solid-state results. Comparison of experimental data for free molecules with a range of state-of-the-art QC calculations will help to evaluate the quality of such theory-approximations. With a set of data from gas-phase and solid-state methods as well as QC, we will be able to study method- or phase-dependence of dispersion interactions. In the first project phase we have demonstrated that our approach indeed provides valuable structural and thermochemical information on the occurrence and strengths of intramolecular dispersion interactions. The objects of study stemmed from own preparative work (e.g. interactions C6H5/C6F5, Cu···Cu or Hg···Hg) and from co-operations with other SPP groups (e.g. alkyl/alkyl in large diamantyl dimers). In some cases we found severe differences between gas-phase experiments and highest-level QC calculations, in others good agreement with some QC methods. We also established new ligand systems for synthesizing volatile dinuclear gold complexes. In this way we learned to generate a range of new molecules for studying certain types of dispersion-dominated interactions in isolated form. In the second funding period we will make use of this knowledge and deepen our understanding of intramolecular dispersion interactions, as well as produce challenging new objects plus experimental data as references for dispersion-corrected QC methods. We also aim at understanding the failure of certain methods for certain types of compounds. The various types of intramolecular interactions to be studied include a) σ∙∙∙ σ interactions in hydrocarbons and organosilanes, b) arene π∙∙∙π interactions, c) σ-hole interactions (halogen and chalcogen bonds), and d) d10∙∙∙d10 (e.g. Au∙∙∙Au, Hg∙∙∙Hg) and d10∙∙∙s2 interactions (e.g. Au∙∙∙Bi). We will also undertake GED structure determinations for at least four other groups in the SPP.