Dynamic covalent chemistry
[1] DCvC has allowed access to complex assemblies such as covalent organic frameworks, molecular knots, polymers, and novel macrocycles.
[2] Not to be confused with dynamic combinatorial chemistry, DCvC concerns only covalent bonding interactions.
The underlying idea is that rapid equilibration allows the coexistence of a variety of different species among which molecules can be selected with desired chemical, pharmaceutical and biological properties.
Dynamic systems are collections of discrete molecular components that can reversibly assemble and disassemble.
With time, the intermediates equilibrate towards the global minimum, corresponding to the lowest overall Gibbs free energy (ΔG°), shown in red on the reaction diagram in figure 1.
cyclophane C2 can be prepared by the irreversible highly diluted reaction of a diol with chlorobromomethane in the presence of sodium hydride.
Reactions used in DCvC must generate thermodynamically stable products to overcome the entropic cost of self-assembly.
Finally, all possible intermediates must be reversible, and the reaction ideally proceeds under conditions that are tolerant of functional groups elsewhere in the molecule.
For example, Schiff base formation can be categorized as a forming new covalent bonds between a carbonyl and primary amine.
Catalysis is always necessary because the barrier of activation between kinetic products and starting materials makes the dynamic reversible process too slow.
[1] A common dynamic covalent building motif is bond formation between a carbon center and a heteroatom such as nitrogen or oxygen.
They have been used more broadly in materials chemistry for molecular switches, covalent organic frameworks, and in self-sorting systems.
Boronic acid condensation (BAC) and disulfide exchange constitute the two main reactions in this category.
[10]Although dynamic covalent chemistry has no practical applications, it has allowed access to a wide variety of supramolecular structures.
[1] Dynamic covalent reactions have recently been used in Systems chemistry to initiate signaling cascades by reversibly releasing protons.
Furthermore, the error-correcting ability inherent to DCvC allows large structures to be made without flaws.
Possible morphologies include infinite covalent 3D frameworks, 2D polymers, or discrete molecular cages.
