Featured Research

from universities, journals, and other organizations

'Yanking' Chemical Bonds With Molecular Wires Speeds Reactions

Date:
March 15, 2006
Source:
Duke University
Summary:
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.

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.



Story Source:

The above story is based on materials provided by Duke University. Note: Materials may be edited for content and length.


Cite This Page:

Duke University. "'Yanking' Chemical Bonds With Molecular Wires Speeds Reactions." ScienceDaily. ScienceDaily, 15 March 2006. <www.sciencedaily.com/releases/2006/03/060314164426.htm>.
Duke University. (2006, March 15). 'Yanking' Chemical Bonds With Molecular Wires Speeds Reactions. ScienceDaily. Retrieved August 21, 2014 from www.sciencedaily.com/releases/2006/03/060314164426.htm
Duke University. "'Yanking' Chemical Bonds With Molecular Wires Speeds Reactions." ScienceDaily. www.sciencedaily.com/releases/2006/03/060314164426.htm (accessed August 21, 2014).

Share This




More Matter & Energy News

Thursday, August 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Flower Power! Dandelions Make Car Tires?

Flower Power! Dandelions Make Car Tires?

Reuters - Business Video Online (Aug. 20, 2014) Forget rolling on rubber, could car drivers soon be traveling on tires made from dandelions? Teams of scientists are racing to breed a type of the yellow flower whose taproot has a milky fluid with tire-grade rubber particles in it. As Joanna Partridge reports, global tire makers are investing millions in research into a new tire source. Video provided by Reuters
Powered by NewsLook.com
Awesome New Camouflage Sheet Was Inspired By Octopus Skin

Awesome New Camouflage Sheet Was Inspired By Octopus Skin

Newsy (Aug. 19, 2014) Scientists have developed a new device that mimics the way octopuses blend in with their surroundings to hide from dangerous predators. Video provided by Newsy
Powered by NewsLook.com
Researcher Testing on-Field Concussion Scanners

Researcher Testing on-Field Concussion Scanners

AP (Aug. 19, 2014) Four Texas high school football programs are trying out an experimental system designed to diagnose concussions on the field. The technology is in response to growing concern over head trauma in America's most watched sport. (Aug. 19) Video provided by AP
Powered by NewsLook.com
Green Power Blooms as Japan Unveils 'hydrangea Solar Cell'

Green Power Blooms as Japan Unveils 'hydrangea Solar Cell'

AFP (Aug. 19, 2014) A solar cell that resembles a flower is offering a new take on green energy in Japan, where one scientist is searching for renewables that look good. Duration: 01:29 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins