Project Details
Projekt
London Dispersion Interactions inside Macrocycles
Applicant
Professor Dr. Werner Nau
Subject Area
Organic Molecular Chemistry - Synthesis and Characterisation
Term
from 2015 to 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 271456295
We propose to investigate the contribution of London dispersion interactions (LDI) to the molecular recognition process of macrocycles, prominently cucurbit[n|urils (CBn) and to the control of chemical reactions inside their inner cavity. CBn are water-soluble macrocyclic host molecules of the molecular container type, that is, they are able to encapsulate numerous organic guests inside their hydrophobic cavity. The driving force for binding inside the inner cavity of CBn is primarily traced back to a hydrophobic effect, but LDI present an important modulator. Out of the original six experimental lines of investigation, five will be further pursued in the second project phase: 1) Building up on our quantification of LDI in the binding of noble gases (He, Ne, Ar, Kr, and Xe) to the smallest CBn homologue, CB5, we plan to study the potential of different docking cations to modulate LDI in the resulting CB5•noble gas•cation complexes. 2) We will extend our investigation on the high-affinity binding of strongly polarizable borate clusters of the type (B12X12)2– to substituted carboranes, which in contrast to the dianionic borate clusters possess a neutral core. In order to dissect solvent effects from LDI, we will also study the solvent isotope effect for this type of complexes. 3) As an example of supramolecular catalysis, we have investigated the dimerization of cyclopentadiene inside CB7, for which we have found a million-fold rate enhancement; this study will be extended to methylcyclopentadiene to introduce chemoselectivity into the catalytic reaction. 4) We propose to assess the relative abundance of inclusion versus exclusion complexes in the gas phase as an interesting approach to study LDI. Through collaborations, we have started to investigate a series of organic ammonium ions with CB6 in the gas phase. For direct comparison, we already determined the binding constants of the ammonium ions to CB6 in water during the first phase of the priority programme. 5) The inversion process of CBn macrocycles in the gas phase will also be examined, which is thought to be driven by intramolecular LDI. Throughout the project, NMR spectroscopy, isothermal titration calorimetry, dye displacement titrations, organic synthesis and quantum-chemical calculations will be used to determine the binding affinities as well as thermodynamic parameters and, thus, to evaluate the importance of LDI.
DFG Programme
Priority Programmes
