Interaction Energies and Dynamics of Acid−Base Pairs Isolated in Cavitands

Abstract

The use of capsules and cavitands in physical organic chemistry is briefly reviewed, and their application to the study of salt bridges is introduced. Carboxylate/ammonium ion pairs are generated within an environment that more or less surrounds the functional groups within a synthetic fixed The barriers to in-out exchange of several amine guests were determined to be in the range from 15 to 24 kcal mol −1 . Some parallels with enzymes are drawn: the receptor folds around the guest species; presents them with inwardly directed functionality; and provides a generally hydrophobic environment and a periphery of secondary amide bonds.

Deciphering the scaling of single-molecule interactions using Jarzynski’s equality

“…The obtained DG JE 0 ¼ 11 AE 1 kT falls within the expected range of 5-15 kT for acid-base bonds in water 26 . Also, DG JE 0 compares reasonably well to interaction free energies calculated for carboxylic acid-amine bonds in water using DFTsimulations 27 , and estimates for the interaction free energy of carboxylic acid cavitands with tertiary amines obtained by NMR 28 , which quote 6-17 kT and 5 kT, respectively.…”

Chemistry and Catalysis in Functional Cavitands

“…Complex D is the double mutant where both interacting sites have been deleted. The electrostatic interaction in the complex formed between 8b and the quinuclidinium cation is then −3.0 ± 0.4 kcal mol −1 using equation (4) (Figure 4) (Purse et al ., 2008). This figure agrees well with the value determined for a buried electrostatic interaction between Asp and Arg in Barnase (-3.3 kcal/mol) (Vaughan et al ., 2002).…”

Bioinspired Self‐Assembly I: Self‐Assembled Structures

“…21 While the majority of these larger structures fall within the realm of metallosupramolecular chemistry, 22 -27 a range of such larger metal-free structures has now also been reported. 8,14,[28][29][30][31][32] A number of the larger polyhedral structures 28,33 mirror the shapes of particular naturally occurring systems such as the virus capsids and the protein enzyme lumazine synthase. The capsids represent a welldefined group of biostructures 34 that serve as the protein shells of viruses and consist of oligomeric structural subunits that enclose the genetic material of the virus.…”