In autumn 2015 the Research Training School on molecular biradicals took up its work at the University of Würzburg. Currently the cooperation between chemists and physicists led to a first result: a publication on a new molecule, which is of interest for organic electronics.
Non-specialists see a dark purple solid that appears to have no specific properties: Experts instead are delighted about a nanographene with a central core composed of 64 carbon atoms, which is characterized by its electron-poor character.
Sabine Seifert, PhD candidate at the chair of organic chemistry II, realized the synthesis and structural characterization of this molecule under supervision of Professor Frank Würthner. Recently, the journal Angewandte Chemie reported on this work in its international edition.
Capacity for up to four electrons
A pyrene precursor which is extended by four naphthalimide moieties builds up the new molecule bearing 64 sp2-hybridized carbon atoms in its central core. These coplanary arranged atoms generate a flat and two-dimensional system, which rises in dimensionality at its corners where bulky sidechains were introduced. The size of this molecule extends over more than one nanometer – one millionth of a millimeter. Its specificity: “We succeeded to synthesize one of the largest electron-poor molecules,” explains Sabine Seifert. According to the PhD student, only few similar synthetic strategies are established so far. “The synthesis in which ten carbon-carbon bonds are formed in one single chemical operation is unprecedented and may be pioneering for the fabrication of hitherto unknown polycyclic aromatic materials”, adds Professor Frank Würthner.
Electron-poor: As a consequence the new molecule has the tendency to take up additional electrons. Thus, the young junior scientist could show that up to four of them can be hosted by this system which therefore becomes interesting for organic electronics. As an organic semiconductor, it could be responsible for electron transport processes and therefore open access to new applications.
Cooperation within the Research Training School
To discover new synthetic strategies and subsequently determine the structures and properties of newly synthesized moleculesis the purpose of the cooperation of the Research Training School 2112, which was initiated at the University of Würzburg last fall with Professor Ingo Fischer as its speaker (Institute of Physical Chemistry). The focus of this program is on so called biradicals – molecules with two unpaired electrons – to which this new nanographen-symstem closely resembles once it has been charged with “only” two electrons. The generation of tri- and tetra-radicals should also be possible and therefore go beyond the aim of the Research Training School.
“We are studying how far the electrons interact with each other, how the spins behave and whether (bi)-radicaloid states can be generated”, explains Sabine Seifert. Among others, biradicals play an important role in combustion processes or atmospheric chemistry, with oxygen and ozone as well known representatives of such systems . Furthermore, their physical properties could be advantageous for the development of new optoelectronic materials. For this reason, it is the goal of the Research Training School to get an even better understanding of the respective properties and to specifically manipulate the physical and chemical characteristics of biradicals. As part of her PhD thesis, Sabine Seifert worked more than two years in the laboratory to accomplish the synthesis of this nanographene-system. The next step will be to vary the side chains and to elaborate the impact of these variations on the properties of such molecules.
An Electron-Poor C64 Nanographene by Palladium-Catalyzed Cascade C-C Bond Formation: One-Pot Synthesis and Single-Crystal Structure Analysis. Sabine Seifert, Kazutaka Shoyama, David Schmidt, and Frank Würthner. Angewandte Chemie, DOI: 10.1002/ange.201601433
Prof. Dr. Frank Würthner, Institut für Organische Chemie der Universität Würzburg
T: (0931) 31-85340, firstname.lastname@example.org
Gunnar Bartsch | Julius-Maximilians-Universität Würzburg
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy