Exploiting the Strong Hydrogen Bond Donor Properties of a Borinic Acid Functionality for Fluoride Anion Recognition.

Borinic acids have typically not been considered as hydrogen bond donor groups in molecular recognition. Described herein is a bifunctional borane/borinic acid derivative (2) in which the two functionalities are connected by a 1,8-biphenylenediyl backbone. Anion binding studies reveal that 2 readily binds a fluoride anion by formation of a unique B-F⋅⋅⋅H-O-B hydrogen bond. This hydrogen bond is characterized by a short H-F distance of 1.79(3) Å and a large coupling constant (1 JHF ) of 57.2 Hz. The magnitude of this interaction, which has also been investigated computationally, augments the fluoride anion binding properties of 2, thus making it compatible with aqueous environments.