Boronic acid-diol condensation, aldehyde-hydrazide condensation, and terpyridine-metal complexation for reconfigurable networks
Dynamic covalent chemistry is a unique class of interactions that exhibit reversible covalent bonds that are thermodynamically stable, yet kinetically reversible with exchange reactions occurring on the time scale of minutes to hours. These interactions can be exploited to direct the assembly to of molecules, polymers, and materials under thermodynamic control. Dynamic covalent chemistry has been an advantageous route for the field of supramolecular chemistry, dynamic combinatorial chemistry, and materials science. Recently, the Anslyn Research Laboratories at the University of Texas at Austin has determined a set of dynamic covalent bonding pairs (boronic acid-diol, aldehyde-hydrazide, thiol-conjugate acceptor, and terpyridine-metal coordination) that exhibit no cross reactivity in a one pot reaction and are controlled by external stimuli’s, such as temperature or pH. This set of dynamic covalent bonding pairs have been coined, Tunable Orthogonal Reversible Covalent (TORC) bonding pairs. To demonstrate the utility of the boronic acid-diol TORC bonding pair’s acidity was experimentally determined using a library of commonly used boronic acids and diols. To build upon the versatility of the boronic acid-diol TORC bonding pair, an optical experimental protocol, amenable to high-throughput procedures, was developed to determine the stereochemistry of alkenes in a solution. Additionally, in collaborative efforts, the aldehyde-hydrazide, and the terpyridine-metal TORC pairs were used to direct the assembly and disassembly of indium tin oxide nanocrystals to create colloidal gels. To highlight the terpyridine-metal coordination assembly, we demonstrated the first thermally reversible colorimetric nanocrystal gel assembly; where the gelation temperature was tuned based on the concentration of chloride. Ultimately, these thermally activated assemblies lead way to innovated advancements in smart materials, like smart thin films. In general, TORC bonding pairs have been showcased in a wide variety of applications to reveal an innovative approach for the creating, designing, and controlling thermodynamic assemblies.