In chemosensor design, one key elementary factor is strong functional group interactions. Previous chapters have extensively discussed noncovalent interactions in sensor design. This chapter is focused on covalent interactions. One important feature of an ideal chemosensor is the reversibility in binding. Otherwise, the "chemosensor" becomes a "reagent" and can only be used in a stoichiometric manner, which severely limits its applications. Owing to the desire for reversibility in binding in a chemosensor, covalent interactions are not commonly used because of the lack of ready reversibility for most covalent bond formation reactions. However, there are a few types of covalent functional interactions that are readily reversible and therefore can be used for the construction of chemosensors. The advantages of using reversible covalent interactions include (i) strong affinity, (ii) intrinsic functional group preference that may help chemosensor selectivity, and (iii) enhanced possibility for the construction of chemosensors with a "built-in" signaling mechanism. The latter point is due to the fact that covalent interactions allow for drastic modifications of the electronic structures of the interacting functional groups and thus their spectroscopic and/or electrochemical properties. One can take advantage of such drastic changes for the generation of a detectable signal. Below, we discuss in detail various covalent interactions that can be used for chemosensor construction.
3.1.1 Boronic-Acid-Based Chemosensors
Among all the covalent functional group interactions, boronic acid stands out as the most commonly used in Chemosensors: Principles, Strategies, and Applications, First Edition. Edited by Binghe Wang and Eric V. Anslyn.