Chemistry – A European Journal
Wiley-VCH Verlag GmbH & Co. KGaA
The interactions of halides with a number of bipodal receptors are examined via quantum chemical methods. The receptors are based upon a dithieno thiophene framework in which two S atoms can engage in a pair of chalcogen bonds with a halide. These two S atoms are 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 are added to the thiophene S atom which is not directly involved in the interaction with the halides. Fluoride is bound the most strongly, followed by Cl-, Br-, and I- in that order. Replacing S by the pnicogen bonds of P strengthens the binding, as does 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 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.
Scheiner, S. I. (2016). Highly Selective Halide Receptors Based on Chalcogen, Pnicogen, and Tetrel Bonds. Chemistry – A European Journal, 22(52), 18850–18858. http://dx.doi.org/10.1002/chem.201603891