Light-powered, artificial molecular pumps: a minimalistic approach

Abstract

SummaryThe realization of artificial molecular motors capable of converting energy into mechanical work is a fascinating challenge of nanotechnology and requires reactive systems that can operate away from chemical equilibrium. This article describes the design and construction of a simple, supramolecular ensemble in which light irradiation causes the directional transit of a macrocycle along a nonsymmetric molecular axle, thus forming the basis for the development of artificial molecular pumps.

Dissipative and Autonomous Square‐Wave Self‐Oscillation of a Macroscopic Hybrid Self‐Assembly under Continuous Light Irradiation

“…Credi and co-workers demonstrated the repetitive unidirectional transit of a macrocycle of azobenzene-pseudorotaxane in solution under the PSS condition, in the absence of macroscopically synchronized transient dynam- ics. [14] In contrast to an isotropic solution, repeated photoisomerization under polarized blue light results in a molecular ordering of azobenzene in condensed materials. Two-dimensional patterns have been formed on azobenzene-containing substrate surfaces [12] or amphiphilic azobenzene monolayer membranes.…”

Wholly Synthetic Molecular Machines

“…Both of these systems, [128,130] however,e xhibit ac ouple of fundamental deficiencies.F irst of all, the unidirectional transport is occurring in solution in supramolecular systems where the rings are threadedo nto ac onstitutionally asymmetric axle from one end out of the bulk solution and then dethreaded from the other end of the pseudorotaxane back into the solution. The result of this on-one-end, off-the-other-endm echanism is that no useful work is done during the operation of the cycle.…”

“…Based on the flood of reviews [24-27, 58, 63, 89, 118, 121] and feature articles, [147,148] not to mention remarkable, high-profile papers [43,53,56,61,87,88,94,108,112,128,135,136,144,146] and news & views, [95,129,137,145] that have surfaced in the scientific literature which enjoyg lamour status duringt he past couple of years, research into wholly synthetic molecular machines appearst o have reached at ippingp oint. If this point in the rise of molecular machines [24,25] has indeed been reached, then the questions which arise are what next and where next?T he latter question is the easier of the two to answer:i ft he history of science tells us anything, it is that applications which find their way into our everyday lives are ap rerequisite for the recognition of an ew field of science.…”

Dethreading of a Photoactive Azobenzene‐Containing Molecular Axle from a Crown Ether Ring: A Computational Investigation

“…Remarkably,t he self-assembly kinetics of R with the EE-A axle is much faster than with the ZZ-A axle, both fort he threading (DG ¼ 6 EE = 15.0 kcal mol À1 , DG ¼ 6 ZZ = 20.9 kcal mol À1 )a nd the dethreading processes (DG ¼ 6 EE = 19.3 kcal mol À1 , DG ¼ 6 ZZ = 24.5 kcal mol À1 ). [13,14] The scope of the present work is to investigate the reasons for the significant differences in the thermodynamic and kinetic behavior of the two threaded complexes,w hich is at the basis of the above mentioned light-powered molecular devices. In other words, [R'EE-A]i sagenuine pseudorotaxane whereas [R'ZZ-A]b ehaves as ar otaxane.I ns uccessive studies, these features were exploitedi namodified system to achieve the chemically-and light-controlledr elative unidirectional transit of the ring along the axle [11] and, eventually,t oc onstruct the first example of an artificial autonomous molecular pump powered by light.…”