Dissipative Assembly of Aqueous Carboxylic Acid Anhydrides Fueled by Carbodiimides

Abstract

Biochemical systems make extensive use of chemically fueled processes (e.g., using ATP), but analogous abiotic systems remain rare. A key challenge is the identification of transformations that can be adapted to a range of applications and make use of readily available chemical fuels. In this context, the generation of transient covalent bonds is a fundamental tool for nonequilibrium systems chemistry. Here, we show that carbodiimides constitute a simple class of chemical fuels for dissipative assembly, taking advantage of their known reactivity to produce (hydrolytically unstable) anhydrides from carboxylic acids in water. Both aliphatic and aromatic anhydrides are formed on convenient time scales using the common, commercially available peptide coupling agent 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide (EDC). An important feature of this reaction is that no part of the carbodiimide is incorporated into the transient species; that is, the fuel is decoupled from the structure-and thus function-of the assembled state. We show that intramolecular anhydride formation of oligo(ethylene glycol) diacids gives macrocycles analogous to crown ethers, representing minimal examples of out-of-equilibrium supramolecular hosts. The kinetics and yields of macrocycle formation respond to cation guests, with the presence of matched cations decreasing their overall production.

Energy consumption in chemical fuel-driven self-assembly

“…3a). 11,[26][27][28][29][30][31][32][33][34] Here, a chemical fuel (F) reacts -either covalently or noncovalentlywith monomer M leading to an activated monomer M* which has the ability to aggregate (A* n ) in a thermodynamically favored process. Contemporaneously a backward reaction takes place which converts M* (or A* n ) back to M (or A n ) accompanied by the release of waste (W).…”

Substrate‐Induced Self‐Assembly of Cooperative Catalysts

“…This has sparked strong interest in the design of chemical‐fuel driven out‐of‐equilibrium systems, in particular related to self‐assembly . The majority of reported examples rely on the covalent modification of building blocks, which changes their propensity to form assemblies . However, driven self‐assembly processes in Nature, that is, fuel‐driven processes that lead to a population of a high‐energy state, rely exquisitely on the use of noncovalent interactions for building block activation .…”

Dynamic Vesicles Formed By Dissipative Self‐Assembly

“…The precursor in our reaction cycle has a C‐terminal aspartic or glutamic acid, such that it carries two carboxylates: one on the C‐terminus and one on its side group. These carboxylates can be condensed into their corresponding cyclic anhydride at the expense of a carbodiimide fuel (Scheme b) . The conversion to the anhydride constitutes the activation reaction.…”

“…These carboxylates can be condensed into their corresponding cyclic anhydride at the expense of a carbodiimide fuel (Scheme 1b). [32,33] The conversion to the anhydride constitutes the activation reaction. As a fuel, we used EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide) which was irreversibly converted into its corresponding urea (waste).…”