Secondly, stopper flexibility has an important influence on the deslipping rate. Thirdly, exchange of a carbonamide for a sulfonamide in the wheel significantly reduces the entropic costs of the deslipping, resulting in a pronounced deslipping rate enhancement. Fourthly, intramolecular hydrogenbonding within the wheel decelerates deslipping by a factor of more than 104.
Substituent effects on axle binding in amide pseudorotaxanes: comparison of NMR titration and ITC data with DFT calculations
作者:Lena Kaufmann、Egor V. Dzyuba、Friedrich Malberg、Nora L. Löw、Matthias Groschke、Boris Brusilowskij、Juhani Huuskonen、Kari Rissanen、Barbara Kirchner、Christoph A. Schalley
DOI:10.1039/c2ob25196e
日期:——
The binding behaviour of differently substituted diamide axle molecules to Hunter/Vögtle tetralactam macrocycles was studied with a combination of NMR titration, isothermal titration calorimetry (ITC) experiments and calculations employing density functional theory (DFT), along with dispersion-corrected exchange-correlation functionals. Guests with alkyl or alkenyl chains attached to the diamide carbonyl groups have a significantly higher binding affinity to the macrocycle than guests with benzoyl amides and their substituted analogues. While the binding of the benzoyl and alkenyl substituted axles is enthalpically driven, the alkyl-substituted guest binds mainly because of a positive binding entropy. The electronic effects of para-substituents at the benzoyl moieties have an influence on the binding affinities. Electron donating substituents increase, while electron-withdrawing substituents decrease the binding energies. The binding affinities obtained from both NMR titration and ITC experiments correlate well with each other. The substituent effects observed in the experimental data are reflected in adiabatic interaction energies calculated with density functional methods. The calculated structures also agree well with pseudorotaxane crystal structures.
Chelate cooperativity effects on the formation of di- and trivalent pseudo[2]rotaxanes with diketopiperazine threads and tetralactam wheels
作者:Nora L. Traulsen、Christoph H.-H. Traulsen、Peter M. Deutinger、Sebastian Müller、Deborah Schmidt、Igor Linder、Christoph A. Schalley
DOI:10.1039/c5ob01687h
日期:——
Double mutant cycle analyses of isothermal titration calorimetry data on di- and trivalent amide pseudorotaxanes provide insight into chelate cooperativity effects on multiply threaded structures.