Connecting the dynamics and reactivity of arylboronic acids to emergent and stimuli-responsive material properties.

Over the past two decades, arylboronic acid-functionalized materials have been used in a variety of sensing and stimuli-responsive scaffolds. Their diverse applications result from the various modes of reactivities of arylboronic acids. Arylboronate ester-crosslinked hydrogels are self-healing because the boronate ester bond is dynamic covalent.

Diazaborines oxidize slowly with HO but rapidly with peroxynitrite in aqueous buffer.

Reactive oxygen species (ROS) such as hydrogen peroxide (HO) and peroxynitrite (ONOO) oxidize arylboronic acids to their corresponding phenols. When used in molecular imaging probes and in ROS-responsive molecules, however, simple arylboronic acids struggle to discriminate between HO and ONOO because of their fast rate of reaction with both ROS. Here, we show that diazaborines (DABs) react slowly with HO but rapidly with peroxynitrite in an aqueous buffer.

Tuning the exchange dynamics of boronic acid hydrazones and oximes with pH and redox control.

Dynamic bonds continually form and dissociate at equilibrium. Carbonyl compounds with proximal boronic acids, including 2-formylphenylboronic acid (2-FPBA), have been reported to form highly dynamic covalent hydrazone and oxime bonds in physiological conditions, but strategies to tune the dynamics have not yet been reported. Here, we characterize the dynamics of 2-FPBA-derived hydrazones and oximes and account for both the rapid rate of formation (∼102-103 M-1 s-1) and the relatively fast rate of hydrolysis (∼10-4 s-1) at physiological pH.

Covalent assembly of heterosequenced macrocycles and molecular cages through orthogonal dynamic covalent chemistry (ODCC).

Shape-persistent heterosequenced 2-D macrocycles and 3-D molecular cages have been prepared in one pot from two or three different monomers, through orthogonal dynamic covalent chemistry using dynamic imine and olefin metathesis.