Spotlights

Light responsive molecular motor winds up helicates

Posted on 2016-11-16

Molecular switch enables non-invasive control of chirality

Researchers in the Netherlands have used a light-sensitive molecular motor to control the chirality of a double-stranded ‘helicate’. The motor mimics the way that nature employs certain enzymes to unwind helical structures such as DNA.

Helicates are polymetallic complexes in which two organic ligands weave around metal centres and each other to form a double helix – similar to the structure famously observed in DNA. They were first discovered in 1987 by Jean-Marie Lehn, who shared a Nobel prize that same year with Donald Cram and Charles Pederson for pioneering work in the field of supramolecular chemistry.

Almost 30 years since the original research on helicates, a team of scientists led by another Nobel laureate, Ben Feringa of Groningen University, has adapted Lehn’s system to make a new type of molecular machine.

The team can dictate the direction two ligands weave around each other in dinuclear copper complexes, by capping the system with a molecular motor – one of the nanoscale machines that saw Feringa awarded with the 2016 Nobel prize, alongside Fraser Stoddart and Jean-Pierre Sauvage. ‘The idea was to use our molecular motor as a multi-state switch,’ explains Feringa. ‘Because it goes through a rotary cycle, we can address different states which have different chirality.’

The rotor is attached to the ends of two oligobipyridine ligands, which eventually form the strands of the helix. When copper is added, the system self-assembles into a helical structure in a favoured chiral configuration. When this system is treated with light and heat, the motor rotates, causing the helix to unravel and eventually reform as the opposite enantiomer. The chirality of helical molecular systems, including certain antibiotics and catalysts, is often crucial to the way that they carry out their biological or chemical functions.

Markus Albrecht, a supramolecular chemist at RWTH Aachen University, Germany, praises the ‘unique example of stereochemical switching of helicates’, adding that the research could pave the way for new ‘systems for control of chemical reactivity, molecular recognition and even with special mechanical properties’.

Bert Meijer, who also works on supramolecular systems at Eindhoven University of Technology, Netherlands, is similarly impressed with the new rotary motor scaffold. Describing the work as ‘a beautiful illustration of why the 2016 Nobel prize in chemistry was given for the design and synthesis of molecular machines’, he adds that ‘in every new contribution of the [Feringa] group, they come closer to mimicking natural molecular machines with very innovative and original designs’.

Looking to the future, Feringa says that the system could be used for the design of new selective catalysts. ‘Metal complexes that have a certain chirality can act as chiral catalysts,’ he says. ‘By using an external stimulus we might be able to change the configuration of the catalyst and as a result the outcome of the product.’

D Zhao et al, Nat. Chem., 2016, DOI: 10.1038/nchem.2668

graphical abstract

https://www.chemistryworld.com/news/light-responsive-molecular-motor-winds-up-helicates/1017698.article

 

Nanomotors change up a gear with metal turbocharge

Posted on 2016-10-19

Metal complexation can speed up molecular motor 32 times

‘We’ve come up with a way to switch gears in nanocars,’ says Sander Wezenberg, a postdoc at the University of Groningen in the Netherlands. Wezenberg is talking about a molecular motor made in Nobel prize winner Ben Feringa’s group that can now be shifted into top gear on demand. By adding a metal to the motor it can be accelerated up to 32 times its normal speed and is the first time dynamic control over the speed of rotation of a molecular motor has ever been demonstrated.

The motor has the classic shape of Feringa’s ‘windmills’, known as overcrowded alkene rotary motors. These windmills are not activated by wind, but light. A few months ago, the team designed a new type of motor sensitive to visible light. To do so, they incorporated two coordinating nitrogen atoms in its lower half and then attached a ruthenium complex to them. ‘We were surprised to see the motor was not only activated by visible light, but also rotated much faster. It was serendipity,’ says Wezenberg. ‘Then we thought about controlling this metal complexation and making it reversible, like a switch.’

Researchers found that certain metals, like zinc, palladium and platinum, could act as regulators. When they coordinate to the windmill, they induce a structural change that increases the rotational speed. ‘Platinum gives us the highest speed,’ says Wezenberg. ‘We can remove the metal adding competing ligands, and then turn the switch back on adding metal again.’ This gives chemists a level of control that was unprecedented in molecular machines. Being able to tune the speed of the motors opens a wide range of opportunities. ‘These motors can be used to power small devices or tiny robots. We envision molecular machines with higher levels of complexity,’ comments Wezenberg.

Steve Goldup, who researches interlocked molecules and molecular machines at the University of Southampton, says ‘this is a real breakthrough. Until now, different speeds could only be achieved designing different motors from scratch. Now, they can tweak the speed without changing the chemical structure of the motor.’ Goldup ponders the possibilities of this discovery. ‘Perhaps we could modify the speed by changing the ligands around the metal, or modifying its oxidation state. In the latter case, the speed of the nanomotor could then be adjusted simply by applying a voltage to the system.’

Goldup also finds fascinating how ‘Feringa makes it look really easy to achieve, when it’s actually really complicated. The simplicity of the solution belies the difficulty of the problem.’

BY FERNANDO GOMOLLÓN-BEL

References

A Faulkner et al, J. Am. Chem. Soc., 2016, DOI: 10.1021/jacs.6b06467

graphical abstract

https://www.chemistryworld.com/news/nanomotors-change-up-a-gear-with-metal-turbocharge/1017570.article

 

No turning back for motorized molecules

Posted on 2016-06-13

It is not easy to design a synthetic molecular motor. As was pointed out nearly 20 years ago, molecular motors are characterized by movement that must be more than random Brownian motion. Our group recently published a unidirectional molecular motor incorporating a rotating axle.

Collins, B. S. L., Kistemaker, J. C. M., Otten, E.& Feringa, B. L. Nature Chem. http://dx.doi.org/10.1038/nchem.2543 (2016).

For more details about the highlight, please see

Nature 534, 187–188 (09 June 2016)

graphical abstract

http://www.nature.com/nature/journal/v534/n7606/full/534187a.html

 

Molecular machines-where have they come from and where are they headed?

Posted on 2016-03-17

Victoria Richards is a science writer based in Cambridge, UK. She recently investigated the world of artificial molecular machines – where have they come from and where are they headed?

For a detailed report, see
http://www.rsc.org/chemistryworld/2016/02/molecular-machines-rotaxanes-macrocycles-nano-walkers

graphical abstract

http://www.rsc.org/chemistryworld/2016/02/molecular-machines-rotaxanes-macrocycles-nano-walkers

 

Molecular machines-where have they come from and where are they headed?

Posted on 2016-03-17

Victoria Richards is a science writer based in Cambridge, UK. She recently investigated the world of artificial molecular machines – where have they come from and where are they headed?

For a detailed report, see
http://www.rsc.org/chemistryworld/2016/02/molecular-machines-rotaxanes-macrocycles-nano-walkers

graphical abstract

http://www.rsc.org/chemistryworld/2016/02/molecular-machines-rotaxanes-macrocycles-nano-walkers

 

Third generation motor highlighted by Foresight Institute

Posted on 2015-11-16

Biological molecular motors are amazing nanomachines that make all life possible, but even smaller artificial molecular motors based upon organic chemistry instead of biological polymers continue to become more complex and better controlled. A hat tip to Nanowerk for reprinting this news release from the University of Groningen in The Netherlands “New molecular motor mimics two wheels on an axle“:

University of Groningen scientists led by Professor of Organic Chemistry Ben Feringa have designed a new type of molecular motor. In contrast to previous designs, this molecule is symmetrical. It comprises two parts, which are connected by a central ‘axle’ and rotate in opposite directions, just like the wheels of a car. The results, which were published … in the journal Nature Chemistry (Nature Chemistry 7, 2015, 890), would be ideal for nano transport systems.


It may sound odd, but from the perspective of the driver, the wheels on the left and right hand side of a car turn in opposite directions. When a car drives forward, the left front wheel turns clockwise and the right front wheel anti-clockwise. This is also the basic design of a new type of molecular motor from the lab of Ben Feringa, the creator of the first light-driven molecular motor back in 1999.

‘If you want a molecular motor to be of any use, you need to be able to control the rotary motion’, says Feringa. Up to now, this was done by using what are known as chiral molecules. These consist of two mirror-image parts, like a left and right hand, which are connected at a central point. ‘These motor molecules are therefore asymmetrical, and this difference between the two halves dictates the way it turns’, Feringa explains.

In Nature Chemistry, Feringa’s group presents the first symmetrical motor molecule with controlled rotary motion. Feringa: ‘This symmetrical motor, which is light-driven just like our other molecular motors, has two rotation axles and two rotating parts.’ The axles are attached to a central part, which is also symmetrical, with the exception of one carbon atom. This atom has two different chemical groups attached to it, which force the rotating parts to turn in opposite directions, as seen from the central part.

Just like a car, this means that the two ‘wheels’ make the molecule move in one direction. ‘This discovery has fantastic implications for realizing autonomous motion on the nanoscale, such as transport over a nano road in a predetermined direction’, Feringa explains. ‘We are now working in our lab to make this type of nano transport a reality.’

The progress over the past decade with many different types of artificial molecular machines has been encouraging. This research is a good example of progress in a sustained development effort.

—James Lewis

graphical abstract

http://www.foresight.org/nanodot/?p=6856

 

Moleculaire motor met twee wielen op één as

Posted on 21-10-2015

Groningse chemici hebben een nieuw type moleculaire motor ontworpen. Het bestaat uit twee groepen, verbonden via een centrale ‘as’ die in een tegenovergestelde richting draaien, net als de wielen van een auto. Het resultaat lijkt ideaal voor een nanotransportsysteem.

door René Fransen

graphical abstract

http://www.kennislink.nl/publicaties/moleculaire-motor-met-twee-wielen-op-een-as

 

The tiniest Lego: a tale of nanoscale motors, rotors, switches and pumps

Posted on 2015-09-07

Inspired by biology, chemists have created a cornucopia of molecular parts that act as switches, motors and ratchets. Now it is time to do something useful with them.

for more details, see
http://www.nature.com/news/the-tiniest-lego-a-tale-of-nanoscale-motors-rotors-switches-and-pumps-1.18262

by Mark Peplow,
Nature 2015, 525, 18–21

graphical abstract

http://www.nature.com/news/the-tiniest-lego-a-tale-of-nanoscale-motors-rotors-switches-and-pumps-1.18262

 

Enatioselective Allylic Alkylation of Ortho-Substituted Cinnamyl Bromides

Posted on 23-06-2013

Highlights on
Synfacts 2015; 11(7): 0729-0730

Enantioselective Allylic Alkylation of Ortho-Substituted Cinnamyl Bromides

Mark Lautens, Thomas Johnson

Significance

The asymmetric allylic alkylation (AAA) reaction is a powerful method for the formation of carbon–carbon bonds in high enantioselectivity. In the realm of copper catalysis, this reaction is known with allylic bromides and Grignard reagents, among other nucleophiles. However, the reaction with ortho-substituted cinnamyl bromides suffers from lower enantioselectivity. These ortho-substituted molecules can be used as precursors to heterocycles. Herein, the authors report a highly enantioselective AAA with ortho-substituted cinnamyl bromides.

Comment

Different ortho-substituents were ­tolerated on the substrate, and products were formed in high enantioselectivity. With EtMgBr, an inverse addition protocol was employed to maximize branched to linear selectivity and/or ee. The use of non-primary alkyl Grignard reagents is not reported.

van der Molen NC, Tiemersma-Wegman TD, Fañanas-Mastral M, Feringa BL.
Regio- and Enantioselective Copper-Catalyzed Allylic Alkylation of Ortho-Substituted Cinnamyl Bromides with Grignard Reagents.

J. Org. Chem. 2015; 80: 4981-4981


graphical abstract
 

Chemical Talking with Living Systems - Molecular Switches Steer Quorum Sensing in Bacteria

Posted on 23-06-2015

Most biological processes are controlled by changes on the molecular level. Therefore, treatment of diseases with small molecules has been highly successful in the past decades. However, controlling the pharmacokinetics of such a chemical compound is difficult, as their action cannot be turned on and off. In recent years molecular switches, which are able to change
their structure by an external stimulus, have been promoted to be able to steer the effect of a molecule after it has been administrated to biological systems. For more details, see: ChemBioChem 10.1002/cbic.201500276

10.1002/cbic.201500276

 

Drugs on demand

Posted on 2015-03-05

By designing photoswitchable groups into drug molecules, they can be turned on and off, at the flick of a light switch. A feature article in Chemistry & Industry about our work on phtopharmacology, reported by Rachel Brazil. (DOI: 10.1002/cind.792_10.x)

graphical abstract
 

Molecular mixers

Posted on 6 October 2014

"Scientists engineer light-driven molecular motors to create a stir." - News item by Chemical & Engineering News' Matt Davenport

graphical abstract

http://cen.acs.org/articles/92/i40/Molecular-Mixers.html

 

Molecular motors aim to pass water

Posted on 24 February 2014

Article in Chemistry World puts the spotlight on research by the Feringa group into manipulating and moving water with molecular motors.

graphical abstract

http://www.rsc.org/chemistryworld/2014/02/molecular-motors-aim-pass-water-light-driven-motion-hydrophobicity

 

Singlet Oxygen Produced at the Flip of a Switch

Posted on 22 January 2014

JACS Spotlight on the paper by Christine Herman.

http://pubs.acs.org/doi/full/10.1021/ja5003586