The degree of twisting of natural helical structures, such as the DNA double-helix, plays an essential role in many important biological functions. Because of their twisted architecture, artificial helices can facilitate the separation and the synthesis of chiral compounds—asymmetric molecules that cannot be superimposed with their mirror image.
New, small spring-like polymer chains, or oligomers, from organic compounds called o-phenylenes have been created by Eisuke Ohta, Takanori Fukushima, Takuzo Aida and colleagues at RIKEN Advanced Science Institute in Wako . These oligomers consist of benzene rings that connect to each other at a sharp angle, leading to their helical structure. The team’s oligomers can change shape and become more rigid when subjected to an electrochemical signal (Fig. 1). They could soon serve as single-molecule machines for application in molecular computers.
Many researchers have investigated molecules that alter their features such as color, luminescence and mode of aggregation when exposed to external stimuli. However, the stimuli-induced change in rigidity demonstrated by the RIKEN team is unprecedented and may open the door to new types of molecular switches.
The researchers synthesized the o-phenylene oligomers using an iterative approach, which allowed them to gradually incorporate electrochemically sensitive units to the oligomer’s backbone.
Ohta explains that while trying to generate the longest o-phenylene oligomers ever synthesized, they noticed that the oligomers possessed highly condensed electron clouds and exhibited a significant reversible difference in rigidity upon removal of one electron during oxidation reactions.
The helical configuration easily causes cyclization—the formation of non-helical structures— which makes the synthesis and investigation of open oligomer chains difficult. The researchers overcame this hurdle by replacing hydrogen atoms positioned at the extremities of the oligomers with so-called ‘nitro functional groups’. Moreover, the octamer, which consists of eight o-phenylene units, was essential for extending the helices while preventing the cyclization, providing long oligomers of up to 48 o-phenylenes.
While purifying their products, the researchers discovered that the nitro-bearing octamer underwent a ‘chiral symmetry-breaking process’, which produced crystals that contained helices with either a left- or right-handed twist. Furthermore, the helices rapidly switched handedness in solution. However, during oxidation these structures contracted, which slowed the switching process between the two chiral states, enhancing their lifetime. These long-lived states resemble 0 and 1 in binary code, making them attractive for optical memory storage.
The researchers are currently examining the chemical and physical properties of these oligomers, which remain unexplored to date. “We want to unveil these properties now,” says Ohta.
The corresponding author for this highlight is based at the Functional Soft Matter Research Group, RIKEN Advanced Science Institute.
 Ohta, E., Sato, H., Ando, S., Kosaka, A., Fukushima, T., Hashizume, D., Yamasaki, M., Hasegawa, K., Muraoka, A., Ushiyama, H., Yamashita, K. & Aida, T. Redox-responsive molecular helices with highly condensed ð-clouds. Nature Chemistry 3, 68–73 (2011).
More genes are active in high-performance maize
19.01.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn
How plants see light
19.01.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
19.01.2018 | Materials Sciences
19.01.2018 | Health and Medicine
19.01.2018 | Physics and Astronomy