High-fidelity Recognition of Organotrifluoroborate Anions (R-BF3 - ) as Designer Guest Molecules.

The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R-BF3 - ). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R-BF3 - , by cyanostar macrocycles that are size-complementary to the inorganic BF4 - progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K+ salts of R-BF3 - anions.