Boronic Acid-Based Bipyridinium Salts as Tunable Receptors for Monosaccharides and α-Hydroxycarboxylates

Several novel diboronic acid-substituted bipyridinium salts were prepared and, using a fluorescent
reporter dye, were tested for their ability to selectively bind various monosaccharides and α-hydroxycarboxylates in an aqueous medium. The fluorescence sensing mechanism relies on the formation of a ground-state charge-transfer complex between the dye and bipyridinium. An X-ray crystal structure of this complex
is described herein. Glucose selectivity over fructose and galactose was achieved by designing the
bipyridinium-based receptors to be capable of attaining a 1:1 receptor/substrate stoichiometry via cooperative
diboronic acid binding.