Theory and example of a small‐molecule motor

Abstract

Conceptual principles for operation of a molecular motor stipulate that such a species must consist of an energy‐consuming catalyst that exhibits within its mechanism temporal overlap of successive catalytic cycles, so as to induce irreversible intramolecular motion during operation. The exothermic hydration reaction of MeCOCHCNCMe3 brought about by catalyst HO2CCH2OCMe(CO2H)2 qualifies as such a process, in the form of serial conversion between canonical carboxylic anhydride structures within the catalyst. The steady‐state kinetic behavior and inactivation by methanol demonstrate the operation of an appropriate repetitive catalytic loop in this case. Copyright © 2003 John Wiley & Sons, Ltd.

Synthetic Molecular Motors and Mechanical Machines

“…Exemplified by the motor proteins from nature, continually operating (autonomous) chemically powered molecular motors may be classified as a subset of catalysts—catalyzing the conversion of high‐energy “fuel” molecules into lower energy products while undergoing a conformational change but returning to the starting state on completion of each cycle. Mock and Ochwat have proposed 14 , which undergoes the catalytic cycle illustrated in Scheme 4, as a minimalist model of a molecular motor 77. In the process of catalyzing the hydration of its ketenimine fuel (red box) to give a carboxamide waste product (blue box), epimerization of the stereogenic center in the motor occurs—formally rotation around a CO bond (as indicated for ( R )‐ 14 in Scheme 4).…”

Artificial molecular motors

“…71,72 In 2003, Mock and Ochwat presented what is perhaps the most basic approach towards a molecular motor design reported thus far (Scheme 10). 73 The tricarboxylate motor oscillates between two anhydride forms and is fueled by an acylketenimine. The process is continuous as long as fuel is present.…”

Synthetic Molecular Machines and Polymer/Monomer Size Switches that Operate Through Dynamic and Non-Dynamic Covalent Changes

“…Mock and Ochwat set up a "simple oscillatory motor that spontaneously operates in solution" [38] and involves a rotary motion. It consists of the conversion of an enantiomer 27a/27b into its mirror image 27b/27a (Fig.…”