The short C–H⋯S contacts found in available structural data for both small molecules and larger biomolecular systems suggest that such contacts are an often overlooked yet important stabilizing interaction.
Supramolecular
anion receptors can be used to study the molecular
recognition properties of the reactive yet biologically critical hydrochalcogenide
anions (HCh–). Achieving selectivity for HCh– over the halides is challenging but necessary for
not only developing future supramolecular probes for HCh– binding and detection, but also for understanding the fundamental
properties that govern these binding and recognition events. Here
we demonstrate that linear free energy relationships (LFERs)including
Hammett and Swain–Lupton plotsreveal a clear difference
in sensitivity to the polarity of an aryl C–H hydrogen bond
(HB) donor for HS– over other HCh– and halides. Analysis using electrostatic potential maps highlights
that this difference in sensitivity results from a preference of the
aryl C–H HB donor for HS– in this host scaffold.
From this study, we demonstrate that LFERs are a powerful tool to
gain interpretative insight into motif design for future anion-selective
supramolecular receptors and highlight the importance of C–H
HB donors for HS– recognition. From our results,
we suggest that aryl C–H HB donors should be investigated in
the next generation of HS– selective receptors based
on the enhanced HS– selectivity over other competing
anions in this system.
Synthetic supramolecular receptors have been widely used to study reversible solution binding of anions; however, few systems target highly-reactive species.
Supramolecular chemistry provides an effective strategy for the molecular recognition of diverse molecules. Significant efforts to design synthetic hosts have enabled the successful binding of many types of guests; however, less is known about how host−guest environments influence binding. Herein, we present a comprehensive study in which we measure the host− guest binding of a bis(arylethynyl phenylurea) host with a chloride guest in eight solvents spanning E T (30) values ranging from nonpolar (40.7 kcal mol −1 ) to polar (47.4 kcal mol −1 ). Polar solvents show significantly weaker binding in comparison to nonpolar solvents, and the bulk solvent polarity parameter, E T (30), shows a linear free-energy relationship with respect to the free energy of binding in the host−guest complex. These studies provide a better understanding of how host−guest binding in flexible receptors is governed by their environments and highlight the importance of host reorganization contributions in the free energy of binding. In addition, these studies highlight that preorganization may not be as important as previously thought for weak binding in which enthalpic contributions are smaller versus in polar solvents where solvent effects are magnified.
Differential sensing is a technique that uses an array of crossreactive receptors to create a unique fingerprint to detect analytes. Over the past two decades significant progress in the field has highlighted the power of this approach, enabling detection with commercially available or synthetically simple sensors, discrimination of structurally similar and challenging analytes, and low concentration detection. In this Concept paper, we briefly review developments in the field and highlight areas for future exploration. We believe there is still much room to grow, particularly in designing biosensor arrays, achieving simultaneous quantification of multiple analytes (i. e., multiplexing), and implementation of more advanced machine learning algorithms in array response analysis.
We highlight a convenient synthesis to selectively deuterate an aryl C–H hydrogen bond donor in a supramolecular anion receptor and use competitive titrations to study the deuterium equilibrium isotope effects (DEIE) in binding HS−, Cl−, and Br−.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.