Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

’Yanking’ chemical bonds with molecular wires speeds reactions

16.03.2006


Using a chain of molecules as an infinitesimal lanyard to tug on a chemical bond about to break, Duke University chemists have found they can speed a complex chemical reaction.



Their unusual manipulative technique can reveal previously unknown details about the evolution of such two-step bond reactions, said assistant Duke chemistry professor Stephen Craig. It might ultimately aid efforts to develop new kinds of polymers that can "heal" themselves after tearing, he said.

Craig, current doctoral student Farrell Kersey and former graduate student Wayne Yount described their discoveries in a research paper published online Friday, March 3, 2006, in the Journal of the American Chemical Society (JACS). The work was funded by the National Science Foundation.


"We probed a reaction in which a bond was being made and a bond was being broken by pulling on the bond being broken with an atomic force microscope (AFM)," said Craig. An AFM detects forces or creates images of surfaces at molecular scales by mechanically probing with a flexible microscopic cantilevered tip.

In their experiments, Craig’s group used an AFM tip to exert almost infinitesimally small tugs on a molecular complex made of pyridine and the metal palladium.

The researchers dangled the pyridine-palladium complex in space as if it were part of a molecular trapeze act, by attaching trapeze "wires" made of atomic chains of the molecule polyethylene glycol (PEG). One PEG chain connected the dangling pyridine-palladium to the AFM’s tip. A separate PEG "wire" anchored the complex underneath onto an underlying surface substrate.

When the AFM’s flexible tip pivoted upward, it pulled on the bond linking the pyridine to the palladium. "This is almost like spring-loading that bond," Craig said.

"As a bond breaks, it stretches," he said. "The distance between the atoms gets further and further. And we could infer from the behavior of this experiment that the rate of the reaction speeded up."

Since the whole array was submerged in a solution of the chemical solvent DMSO, the bond was already under pressure before the AFM began its work, he said.

"Because this solvent was present in excessive amounts, it wanted to form a bond with the palladium," he said. But the nature of that reaction requires the DMSO-palladium bond to form first before the palladium and pyridine could sever their connection, he added.

The Duke chemists sought to study how the sequence of bond forming and breaking would be affected if they artificially stretched the palladium-pyridine bond towards the breaking point.

They found that, although the pace of the reaction was accelerated, the order of bond forming and breaking did not change. "We could spring-load the bond enough so it sought to break very quickly. But the reaction still waited for the DMSO to bond to the palladium before the pyridine came off," he said.

The researchers also found that, when they repeated the experiment with a palladium-pyridine complex incorporating a modified pyridine, the response to pulling on the bond was the same even though the energy levels needed for bond-breaking were different.

These findings "are absolutely consistent with some very fundamental notions about the way energy is exchanged in chemical reactions," Craig said. "But to my knowledge it’s not an experiment that anyone else has done to test whether that was the case. This could lead to a more sophisticated understanding of the way reactions happen at their most fundamental levels."

According to Craig, additional studies into the order and consequences of chemical bond-breaking might also aid the discovery of new materials. "Someone might try to design certain types of molecules that would respond to mechanical stresses by breaking in a way that’s desirable," he said.

For example, he said such research might aid researchers like him who work on "self-healing polymers." Those are molecules in the early stages of development that would release chemicals to repair newly formed tears and cracks.

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu

More articles from Life Sciences:

nachricht Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY

nachricht NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

Computer model predicts how fracturing metallic glass releases energy at the atomic level

20.07.2018 | Physics and Astronomy

Relax, just break it

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>