Boronic acid-substituted viologen

A more recent approach to designing direct fluorescent indicators for glucose involves two-component boronic acid sensors, where the fluorophore—usually anionic in nature—is quenched by a physically separate boronic acid-substituted viologen receptor. As the saccharide binds with the receptor, the quenching efficiency of the viologen is reduced, resulting in an increased emission intensity of the fluorophore (Figure 10.8). 

Background and Illustration of Two-Component Glucose Sensing—Pyranine (HPTS) and a Boronic Acid-Substituted Viologen (BBV )... 

In the first of these studies, the boronic acid-substituted viologens were used to quench the fluorescence of HPTS. Results are shown in Figure 5.11. 

D. B. Cordes, S. Gamsey and B. Singaram, Fluorescent quantum dots with boronic acid substituted viologens to sense glucose in aqueous solution, Angem Chem., Int. Ed., 2006,45(23), 3829-3832. 

Comparison of quenching efficacy for and o-BBV indicated that the addition of the boronic acids to o-BBV had little effect on the quenching interaction. This similarity was not always observed in comparison of other viologens with their boronic acid-substituted analogues (Seetion 5.3.2). The Stern-Volmer plots for BV, and o-BBV are given in Figure 5.2. 

After some time, a modest library of over 20 strueturally unique, boronic acid-modified viologens was prepared. These ineluded variously substituted viologens based on the 3,3 -, 3,4 -, and 4,4 -bipyridinium cores and a series of interesting bis-viologens in which two bipyridinium units were combined in a single eompound. While the positioning of boronic acids clearly... 

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