Lorand and Edwards reported the ability of boronic acids to form complexes with 1,2- and 1,3- diols. In addition it was discovered that D-fructose formed a 1:1 fructose-boronic acid complex and D-glucose formed a 1:2 glucose-boronic acid complex [
5]. The strength of the boronic acid binding to monosaccharides is determined by the orientation and relative position of hydroxyl groups. In aqueous solution fructose predominates in the furanose form with a
syn-periplanar pair of hydroxyl groups resulting in a strong binding constant with boronic acids [
4]. As a result, a number of aryl boronic acid-based sensors have been developed for the detection of monosaccharides which exploit the difference in binding stoichiometry and inherent binding affinity to achieve either D-fructose or D-glucose selectivity [
4,
6–
8]. More specifically, in 1994, James et al
. developed an anthracene-containing mono boronic acid derivative as a photoinduced electron transfer (PET) fluorescence probe for the detection of fructose (Fig. 1) [
9]. In this system, it was discovered that
ortho-aminomethylphenylboronic acid functionality facilitated the detection of fructose in neutral aqueous solution. This pioneering work has led to the development of other
ortho-aminomethylphenylboronic acid-containing fluorescence sensors improving selectivity, increasing excitation/emission profile and binding affinities [
10–
12]. While there was never any doubt that the
ortho-aminomethylphenylboronic acid group was important to improve saccharide binding at neutral pH the mechanism of action had been under debate for a number of years [
13–
15]. Recently, the debate was concluded and the fluorescence enhancement on saccharide binding is caused by modulation of internal conversion resulting in different levels of quenching. Initially, before saccharide binding the free
-B(OH)
2 groups quench the fluorescence by internal conversion, then when saccharides bind the
-B(OR)
2 groups formed have reduced internal conversion and less quenching resulting in an enhanced fluorescence [
16].