Mechanically Processive Motion in Synthetic Molecular-level Structures: Transition Metal Complexes that can Walk!
Lead Research Organisation:
University of Edinburgh
Department Name: Sch of Chemistry
Abstract
The aim of this research project is to make molecular motors and machines which, like many biological motors and machines, move along tracks. The machines we use in everyday life are made up of assemblies of moving parts (cogs, wheels, spindles, pistons etc), the movement of each of which is used to perform a task necessary for the overall function of the machine. But what happens when we try to make such things very small, can we make molecular-sized machines? The answer is yes, but their designs are not simple or obvious. Our intuition, formed by the everyday observation of the way large machines work, fails when we consider molecular-sized structures. Macroscopic objects remain stationary until given a push / an energy input / but molecular sized objects are constantly in motion (Brownian motion) and energy must be expended to stop them moving, or to cause them to move in one direction only. For this reason, scaling down motors and engines from the macroscopic world to the molecular level simply does not work, we have to find another solution. For this project we propose to follow a strategy that biology has found through billions of years of evolution, i.e. make machines that move along tracks, exploiting rather than resisting Brownian motion. The ultimate outcome of the proposal could be a generation of artificial nanomachines capable of transporting a tiny cargo on molecular length scales.
Organisations
People |
ORCID iD |
| David Leigh (Principal Investigator) | |
| Paul Lusby (Co-Investigator) |
Publications
Beves JE
(2014)
Toward metal complexes that can directionally walk along tracks: controlled stepping of a molecular biped with a palladium(II) foot.
in Journal of the American Chemical Society
D'Souza DM
(2010)
Nitrone [2]rotaxanes: simultaneous chemical protection and electrochemical activation of a functional group.
in Journal of the American Chemical Society
Leigh DA
(2010)
Improved dynamics and positional bias with a second generation palladium(II)-complexed molecular shuttle.
in Chemical communications (Cambridge, England)
| Description | Nature's use of 'mechanical' molecular-level structures has inspired chemists to synthesize molecular analogues of some of the fundamental components of machinery from the macroscopic world. The ultimate objective of such studies is to create relatively simple synthetic devices or materials that can, like their far more complex biological counterparts, carry out tasks by controlled molecular-level mechanical motion. However, the artificial prototypical molecular machines prepared thus far fall well short of the control over motion exhibited by biological systems. The goal of this research project is to make mechanically processive chemical structures from first principles; i.e. to design, synthesise, operate and characterise wholly synthetic molecular structures which progressively advance directionally along a molecular 'track' in response to stimuli. To this end we have developed a second generation pH-switchable Pd(II)-complexed molecular shuttle which shows significantly increased rates of shuttling compared to the first generation system and also exhibits better positional discrimination of the macrocycle, somewhat surprisingly, in both chemical states of the rotaxane thread [Chem Commun, 46, 2382-2384 (2010)]. We have also discovered a new route towards the synthesis of 2-rotaxanes that is simple and high yielding - by utilizing the powerful hydrogen-bond-accepting properties of nitrones [J Am Chem Soc, 132, 9465-9470 (2010)]. Significantly, we have designed, synthesised, and demonstrated the operation of a bimetallic molecular biped on a three-foothold track - a small-molecule synthetic molecular "walker" that features a palladium(II) complex "foot" that can be selectively stepped between 2 different footholds on the track via reversible protonation while the walker remains attached to the track throughout by means of a kinetically inert platinum(II) complex foot [J Am Chem Soc, 136, 2094-2100 (2014)]. Such systems should prove useful in the development of switchable, metastable components for advanced molecular machinery, most notably linear molecular motors in the form of synthetic small-molecule walkers. |
| Exploitation Route | The new synthetic methodologies and improved level of control over the coordination mechanisms should prove useful for the development of switchable, metastable, components for advanced molecular machinery, including Brownian ratchets and synthetic molecular walkers. |
| Sectors | Chemicals,Education |