title: Highly Selective Halide Receptors Based on Chalcogen, Pnicogen, and Tetrel Bonds.
abstract: The interactions of halides with a number of bipodal receptors were examined by quantum chemical methods. The receptors were based on a dithieno thiophene framework in which two S atoms can engage in a pair of chalcogen bonds with a halide. These two S atoms were replaced by P and As atoms to compare chalcogen with pnicogen bonding, and by Ge which engages in tetrel bonds with the receptor. Zero, one, and two O atoms were added to the thiophene S atom which is not directly involved in the interaction with the halides. Fluoride bound the most strongly, followed by Cl-, Br-, and I-, respectively. Replacing S by the pnicogen bonds of P strengthened the binding, as did moving down to As in the third row of the periodic table. A further large increment is associated with the switch to the tetrel bonds of Ge. Even though the thiophene S atom is remote from the binding site, each additional O atom added to it raises the binding energy, which can be quite large, as much as 63 kcal mol-1for the Ge⋅⋅⋅F-interaction. The receptors have a pronounced selectivity for F-over the other halides, as high as 27 orders of magnitude. The data suggest that incorporation of tetrel atoms may lead to new and more powerful halide receptors.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT, 84322-0300, USA.
authors.forename: Steve
authors.initials: S
authors.lastname: Scheiner
keywords: density functional calculations; equilibrium constants; free energy; germanium; natural bond orbital