Pyrroles, which are rings containing one nitrogen and four carbon atoms, are essential components of our red hemoglobin as well as the green chlorophyll in plants. Japanese researchers led by Hiromitsu Maeda at Risumeikan University have now also used this molecular motif in the construction of new nanostructured materials:
They combined planar pyrrole-containing negatively charged complexes with similarly planar, positively charged organic ions. As the scientists report in the journal Angewandte Chemie, they were able to produce fibers and soft materials, such as supramolecular gels and liquid crystals.
Salts consist of cations and anions—positively and negatively charged particles. Most salts organize themselves into ordered crystals that are held together through the electrostatic attraction between the oppositely charged ions. However, there are also ionic liquids, which are salts that exist as melts at room temperature. The size and geometry of the ions involved prevent the formation of a strong crystal lattice. Ionic liquid crystals are another interesting class of materials. Liquid crystals are fluid like a liquid, though the particles in them are arranged in an ordered state. In addition, there are other materials that are more organized but whose components maintain a certain degree of mobility. These are of interest for the development of ferroelectric memory devices.
The Japanese researchers selected planar ions to build up self-organized materials in which the charged components are stacked in an alternating fashion. The first component is a planar complex made from a small inorganic ion and an organic receptor (receptor–anion complex). The critical structural element of the receptor contains two pyrroles bound into what is known as a ð-conjugated environment. This means that some of the electrons are freely mobile as an “electron cloud” over a large area of the molecule. The ligand surrounds the anion on three sides. The second component is a disk-shaped organic cation made from an aromatic ring system, which also has an electron cloud. Because of the electrostatic attraction between oppositely charged ions, and also attractive interactions between the electron clouds, these anions and cations always stack themselves into alternating columnar units.
Depending on the type of additional side-groups on the components, the columns organize into various structures, such as fibers, supramolecular gels, or liquid crystals. Such alternating stacks of oppositely charged components (charge-by-charge assembly) has proven to be a successful concept for the production of novel materials from organic ions.
Author: Hiromitsu Maeda, Ritsumeikan University, Kusatsu (Japan), http://www.ritsumei.ac.jp/pharmacy/maeda/frame-10en.html
Title: Oriented Salts: Dimension-Controlled Assemblies from Planar Receptor–Anion Complexes
Angewandte Chemie International Edition 2010, 49, No. 52, 10079–10083, Permalink to the article: http://dx.doi.org/10.1002/anie.201006356
Hiromitsu Maeda | Angewandte Chemie
Navigational view of the brain thanks to powerful X-rays
18.10.2017 | Georgia Institute of Technology
Separating methane and CO2 will become more efficient
18.10.2017 | KU Leuven
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
18.10.2017 | Materials Sciences
18.10.2017 | Physics and Astronomy
18.10.2017 | Physics and Astronomy