0000000000471220
AUTHOR
Egor V. Dzyuba
Gas-phase H/D-exchange reactions on resorcinarene and pyrogallarene capsules: Proton transport through a one-dimensional Grotthuss mechanism
Hydrogen/deuterium exchange (HDX) experiments can be used to examine the gas-phase structure of hydrogen-bonded dimeric resorcinarene and pyrogallarene capsules. Already the qualitative comparison of the isotope exchange rates of different host–guest complexes with Cs+, tetramethyl ammonium (TMA+) and tetraethyl ammonium (TEA+) as the guest cations provides insight into the H/D-exchange mechanisms and with it, into the capsules' gas-phase ion structures. The smaller Cs+cations bind inside dimeric capsules with an intact seam of hydrogen bonds between the two monomers. Larger cations such as TEA+ lead to capsules with partially disrupted seams of hydrogen bonds. A fast isotope exchange is on…
Substituent effects on axle binding in amide pseudorotaxanes: comparison of NMR titration and ITC data with DFT calculations
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 bindi…
Chelate Cooperativity and Spacer Length Effects on the Assembly Thermodynamics and Kinetics of Divalent Pseudorotaxanes
Homo- and heterodivalent crown-ammonium pseudorotaxanes with different spacers connecting the two axle ammonium binding sites have been synthesized and characterized by NMR spectroscopy and ESI mass spectrometry. The homodivalent pseudorotaxanes are investigated with respect to the thermodynamics of divalent binding and to chelate cooperativity. The shortest spacer exhibits a chelate cooperativity much stronger than that of the longer spacers. On the basis of crystal structure, this can be explained by a noninnocent spacer, which contributes to the binding strength in addition to the two binding sites. Already very subtle changes in the spacer length, i.e., the introduction of an additional…