Highly Selective Halide Receptors Based on Chalcogen, Pnicogen, and Tetrel Bonds

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−1 for 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. Over the bond: The interactions of halides with a number of bipodal dithieno thiophene derived receptors were examined by quantum chemical methods. Chalcogen, pnicogen and tetrel bonding with the receptors were studied (see figure). The data suggest that incorporation of tetrel atoms may lead to new and more powerful halide receptors.