A catalysis-driven artificial molecular pump

Abstract

All biological pumps are autonomous catalysts; they maintain the out-of-equilibrium conditions of the cell by harnessing the energy released from their catalytic decomposition of a chemical fuel. 1-3 A number of artificial molecular pumps have been reported to date, 4 however they are all either fueled by light 5-10 or require repetitive sequential additions of reagents or varying of an electric potential during each cycle to operate 11-16 . Here we report on an autonomous chemicallyfueled information ratchet 17-20 that in the presence of fuel continuously pumps crown ether macrocycles from bulk solution onto a molecular axle without the need for further intervention. The mechanism uses the position of a crown ether on an axle to both promote barrier attachment behind it upon threading and to suppress subsequent barrier removal until the ring has migrated to a catchment region. Tuning the dynamics of both processes 20, 21 enables the molecular machine 22-25 to continuously pump macrocycles from their lowest energy state in bulk solution to a higher energy state on the axle. The ratchet action is experimentally demonstrated by the progressive pumping of up to three macrocycles onto the axle from bulk solution under conditions where barrier formation and removal occur continuously. The out-of-equilibrium [n]rotaxanes (characterised with n up to 4) are maintained for as long as unreacted fuel is present, after which the rings slowly de-thread. The use of catalysis to drive artificial molecular pumps opens up new opportunities, insights and research directions at the interface of catalysis and molecular machinery. Main The structure and mode of operation of the catalysis-driven molecular pump, 1, is shown in Fig. 1. One end of the axle is permanently blocked by a bulky triarylmethine group (brown); the other end of the axle (the N-terminus) is open for threading when in the form of a benzyl amine group (orange). The axle includes a chain of triazole heterocycles linked by short, propyl (-(CH 2 ) 3 -), spacers. Triazoles only

Autonomous Non-Equilibrium Self-Assembly and Molecular Movements Powered by Electrical Energy

“…Remarkably, such energy efficiency is significantly higher than those of other autonomous artificial systems reported to date. 15,18,24,25,48 We have operated our system also under opposite boundary conditions, i.e., Etip = -0.8 and Esub = 0 V, (see SI Section 6,7, Figures S8,S18,S19) proving that multiple non-equilibrium steady-states are experimentally accessible using this system. 49 While the recorded current (-0.8 nA) is similar to the one measured under opposite boundary conditions, the distribution of species is completely different.…”

“…In fact, these devices ultimately catalyze the decomposition of their fuel while undergoing structural transformations. Inspired by natural systems, chemists have developed autonomous molecular machines such as light- 15,16,17 and chemically-driven 18 rotary motors, switches, 19,20,21,22,23 pumps, 24,25 walkers, 26 and actuators. 27,28,,29 Figure 1.…”

Controllable photomechanical bending of metal-organic rotaxane crystals facilitated by regioselective confined-space photodimerization

“…To date, most molecular machine systems are designed to work in solution where each work unit is isolated from each other and functions independently and incoherently. For example, a variety of molecular machines reported so far including molecular switches 20 , 21 , molecular pump 22 , molecular motors 23 – 25 , molecular muscle 26 , 27 , and molecular robot 28 are capable of making increasingly complex operations in aqueous or nonaqueous environments, where different sets of supramolecular motifs are dispersed and separated individually in solution. However, when extended to a solid-state system with significantly shortened intermolecular distances and massive intermolecular interactions that is dramatically different from a solution environment, it is still challenging to construct MIM-based molecular assemblies with structure dynamics in solid.…”

Synthesis of Functional Building Blocks for Type III-B Rotaxane Dendrimer

“…Such an entanglement between the macrocycles and threads in space through a non-covalent interaction is known as a mechanical bond [1], where these components cannot be separated until the chemical bond breaks or distorts within the atom of the components. Rotaxanes have been widely applied in molecular switching [2,3], molecular pumps [4][5][6], molecular motors [7], molecular machines [8] and organocatalysis [9,10]. Dendrimers are another class of highly ordered, hyperbranched macromolecules, composed of a repeating dendron unit with an exact molecular weight [11].…”