Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Materials: Two ways to tame a radical

25.04.2013
Trapping free electrons with polycyclic aromatic molecules creates materials with enhanced optical, electronic and magnetic properties

Replacing traditional semiconductors with flexible and lightweight organic components has the potential to realize significant cost savings for manufacturers. Recently, a promising class of organic materials known as open-shell polycyclic aromatic hydrocarbons (PAHs) has gained researchers' attention.

These molecules consist of interlocked, benzene-like rings and contain unpaired electrons, or ‘free-radical’ centers. Interactions between the radical centers and aromatic electrons make these compounds extremely responsive to light- and electron-based stimuli. Unfortunately, these same radical electrons can quickly degrade PAH chemical structures, rendering them unusable.

Jishan Wu from the A*STAR Institute of Materials Research and Engineering in Singapore and an international team of co-workers have now devised a new stabilization strategy that promises to make open-shell PAHs even more practical1. Through clever modification of a prototypical compound known as Chichibabin’s hydrocarbon, the team has produced two types of PAHs that retain active radical centers for unprecedented amounts of time.

Chichibabin’s hydrocarbon has a sextet of aromatic rings that thermodynamically stabilize radical centers. However, it also has a strong chemical affinity for oxygen atoms and tends to polymerize in their presence. To resolve this issue, Wu and co-workers used a process known as benzannulation to add four additional aromatic benzene rings to the PAH framework. They anticipated this design could enhance thermodynamic stability and block kinetic polymerization interactions.

When the researchers chemically excited the tetrabenzo-Chichibabin’s hydrocarbon to an open-shell system, they saw that the radical centers remained active for an unusually long time — two full days — before returning to the low-energy ground state. Using a combination of high-resolution spectroscopy and theoretical calculations, the team discovered the radical’s benzene rings were oriented at right angles to one another, while the ground-state compound had a relatively flat, butterfly-like ring layout. The large energy barrier between these two geometries kept the radical active. “This opens the possibility of accessing each form of the PAH molecule and understanding its physical properties,” says Wu.

The researchers also modified the tetrabenzo-Chichibabin’s hydrocarbon with aromatic fluorenyl rings that have well-known radical stabilizing effects. In fact, the stabilizing capacity of this compound proved so strong that the open-shell radical became the lowest-energy state, and the molecule remained stable for months under ambient air and light conditions.

Experiments revealed these new open-shell PAHs to have valuable properties including enhanced two-photon absorption, a strong magnetic response and multiple redox states. Wu notes that these findings may lead to the development of better photodynamic therapies and magnetic imaging techniques in the future.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering

Journal information

Zeng, Z., Sung, Y. M., Bao, N., Tan, D., Lee, R. et al. Stable tetrabenzo-Chichibabin’s hydrocarbons: Tunable ground state and unusual transition between their closed-shell and open-shell resonance forms. Journal of the American Chemical Society 134, 14513–14525 (2012).

A*STAR Research | Research asia research news
Further information:
http://www.research.a-star.edu.sg/research/6662
http://www.researchsea.com

Further reports about: benzene rings chemical structure organic material oxygen atom

More articles from Materials Sciences:

nachricht Electron tomography technique leads to 3-D reconstructions at the nanoscale
24.05.2018 | The Optical Society

nachricht These could revolutionize the world
24.05.2018 | Vanderbilt University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>