Substituent Effects on Transient, Carbodiimide-Induced Geometry Changes in Diphenic Acids

Abstract

Nucleotide-induced conformational changes in motor proteins are key to many important cell functions. Inspired by this biological behavior, we report a simple chemically fueled system that exhibits carbodiimide-induced geometry changes. Bridging via transient anhydride formation leads to a significant reduction of the twist about the biaryl bond of substituted diphenic acids, giving a simple molecular clamp. The kinetics are welldescribed by a simple mechanism, allowing structure−property effects to be determined. The kinetic parameters can be used to derive important characteristics of the system such as the efficiencies (anhydride yields), maximum anhydride concentrations, and overall lifetimes. Transient diphenic anhydrides tolerate steric hindrance ortho to the biaryl bond but are significantly affected by electronic effects, with electron-deficient substituents giving lower yields, peak conversions, and lifetimes. The results provide useful guidelines for the design of functional systems incorporating diphenic acid units.

Carbodiimide‐Induced Formation of Transient Polyether Cages**

“…[15,16] This chemistry has been applied, for example, to the generation of transient gels, [15,17,18] other assemblies, [19,20] and macrocycles, [16,21] and to the modulation of materials properties [22,23] and driving of intramolecular motion. [24,25] In previous work, [16] we showed that anhydride-based crown ethers could be generated by the action of a carbodiimides. An example is shown in Scheme 1a: when an aqueous solution of diacid TEG-Ac is treated with the carbodiimide N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC), the macrocycle TEG-An is formed along with acyclic oligomers (not shown).…”

“…Among the most versatile fuel reactions is the formation of anhydrides or activated esters by the hydration of carbodiimides [15,16] . This chemistry has been applied, for example, to the generation of transient gels, [15,17,18] other assemblies, [19,20] and macrocycles, [16,21] and to the modulation of materials properties [22,23] and driving of intramolecular motion [24,25] …”

A Carbodiimide-Fueled Reaction Cycle That Forms Transient 5(4H)-Oxazolones

“…Thus, several chemically fueled reaction cycles have been designed to regulate molecules. The energy transduced by these cycles can come from the oxidation of reducing agents, − hydrolysis of methylating agents, hydration of carbodiimides, − and hydrolysis of ATP. , These cycles lead to a range of assemblies, including fibers, − droplets, , vesicles, micelles, , colloids, , and particle clusters. , A well-studied cycle produces energy by hydrating carbodiimides. , In these cycles, carboxylates react with EDC (1-ethyl-3-(3-(dimethylamino)­propyl)­carbodiimide) to form an O -acylurea intermediate. A second carboxylate attacks this intermediate to form the anhydride product.…”

Controlling the Conformation of 2-Dimethylaminobiphenyls by Transient Intramolecular Hydrogen Bonding

“…4 In the first case, a chiral, enantiopure carbodiimide is used as a fuel to drive the unidirectional motion about the single bond joining two conveniently substituted aromatic rings, namely, a 2-carboxy-phenyl group and a 2-carboxy-N-pyrrolyl group (1, Figure 1). This astonishing achievement has been made possible by previous findings concerning (i) the use of a carbodiimide (EDC) as a fuel to temporally control the conformation of the single bond between two phenyl groups, both substituted with a carboxylic function in the ortho position (2, Figure 1) by Hartley and co-workers 5 and (ii) the exploitation of the same kind of fuel to drive the motions of a rotaxane-based information ratchet by Leigh and co-workers. 6 Addition of the carbodiimide fuel to 1 or 2 induces the transient formation of an intramolecular anhydride bond, which temporarily limits the rotation about the single bond between the aromatic rings (see Figure 1, red bond in 1 and 2).…”