Anion Receptors Composed of Hydrogen- and Halogen-Bond Donor Groups: Modulating Selectivity With Combinations of Distinct Noncovalent Interactions

Abstract

Studies of a series of urea-based anion receptors designed to probe the potential for anion recognition through combinations of hydrogen and halogen bonding are presented. Proton- and fluorine-NMR spectroscopy indicates that the two interactions act in concert to achieve binding of certain anions, a conclusion supported by computational studies. Replacement of the halogen-bond donating iodine substituent by fluorine (which does not participate in halogen bonding) enables estimation of the contribution of this interaction to the free energy of anion binding. Evidence for attractive contacts between anions and electron-deficient arenes arising from the use of perfluoroarene-functionalized ureas as control receptors is also discussed. The magnitude of the free energy contribution of halogen bonding depends both on the geometric features of the group linking the hydrogen- and halogen-bond donor groups and on the identity of the bound anion. The results are interpreted in relation to fundamental features of the halogen-bonding interaction, including its directionality and unusual preference for halides over oxoanions. Cooperation between two distinct noncovalent interactions leads to unusual effects on receptor selectivity, a result of fundamental differences in the interactions of halogen- and hydrogen-bond donor groups with anions.

Transmembrane anion transport mediated by halogen-bond donors

“…Halogen bonds form between nucleophilic acceptors, such as anions, and highly localized positive-charge density on halogen atoms appearing on the side opposite to the covalent bond [13][14][15][16][17][18][19][20][21][22] . They are most prominent with iodine atoms but occur, to a lesser extent, also with the less polarizable bromine, chlorine, and even fluorine (Fig.…”

“…Routinely exploited in crystal engineering 14 , halogen bonds are attracting only recently some attention for rational drug design 16 , anion binding 17,18 and catalysis 19,20 . Whereas the special behaviour of molecular iodine (bp = 184 °C) has been noticed early on 21,22 , contributions of organic halogen bonds to the transport of anion across lipid bilayer membranes have been suspected last year, for the first time 13 .…”

Contributions of Various Noncovalent Bonds to the Interaction between an Amide and S‐Containing Molecules

“…Geometries were optimized at the ab initio MP2/aug-cc-pVDZ level which has been shown to be of high accuracy, especially for weak intermolecular interactions of the type of interest here [35,[47][48][49][50][51][52] where the data are in close accord with CCSD(T) values with larger basis sets [38,53,54] and in excellent agreement with experimental energetics [55] . Binding energies were computed as the difference in energy between the dimer, and the sum of the optimized energies of the isolated monomers, corrected for basis set superposition error by the counterpoise procedure [56] .…”

Supramolekulare Chemie von Anionen: von der Erkennung zur chemischen Anwendung

“…[83] Halogen-und Wasserstoffbrücken wurden auch gemeinsam zur Anionenbindung genutzt. Taylor und Mitarbeiter [84] Sie beobachteten einen deutlich hçheren Beitrag der Halogenidbrücken im Fall der Halogenide verglichen mit Dihydrogenphosphat (Abbildung 21).…”