Molecular snakes change into ladders – potential constructing blocks for electronics


Nov 16, 2021

(Nanowerk Information) Researchers from the Universities of Bonn and Regensburg transfer packets of vitality alongside a molecular ladder product of a whole bunch of benzene rings. Such polymers can doubtlessly be used to design new shows based mostly on natural light-emitting diodes, or for photo voltaic cells. The extraordinary materials is now described within the journal Nature Communications (“Nanoscale pi-conjugated ladders”). Within the nineteenth century, the scientific group puzzled over how the atoms within the mysterious compound benzene had been organized. This “fragrant” molecule quickly proved to have a surprisingly easy construction: It consisted of six carbon and 6 hydrogen atoms. However how might these twelve atoms prepare themselves in area to type a chemically secure object? The chemist Friedrich August Kekulé, later professor on the College of Bonn, introduced mild into the darkness. Legend has it that he sat dozing by the hearth within the winter of 1861. Kekulé all of a sudden had a imaginative and prescient of a snake devouring its personal tail. He realized that the carbon atoms of benzene have to be organized in a circle, much like a small wagon wheel. “This dream finally laid the muse for the huge growth of the chemical trade towards the tip of the nineteenth century,” says Prof. Sigurd Höger of the Kekulé Institute of Natural Chemistry and Biochemistry on the College of Bonn, who’s a member of the Transdisciplinary Analysis Space “Constructing Blocks of Matter and Elementary Interactions” on the College of Bonn. Benzene is a crucial constructing block for paints, prescribed drugs and plastics, for instance. A packet of vitality is generated on a molecular ladder by the absorption of sunshine. The background picture reveals an actual measurement of the ladder construction with a scanning tunneling microscope. (Picture: Joshua Bahr and Tristan Keller)

Lots of of benzene rings within the form of a ladder

Though the wheel is commonly touted as mankind’s oldest invention, the ladder is definitely fairly a bit older. Kekulé’s successors on the College of Bonn had lengthy been dreaming of molecules within the form of a ladder, consisting of a whole bunch of benzene rings. The researchers from the Kekulé Institute and the Mulliken Heart for Theoretical Chemistry on the College of Bonn, along with a workforce led by Prof. John Lupton from the Institute of Experimental and Utilized Physics on the College of Regensburg, have now constructed such a molecular ladder. It is a molecule with two tracks of so-called “conjugated polymers”, by which double and single bonds alternate between the carbon atoms. They make up the rails that you simply maintain on to when climbing up an odd ladder. The researchers first designed a precursor compound that contained solely a single polymer chain and connected polymerizable teams – a versatile “snake.” For a few of the materials, the second rail of the ladder was then fashioned in a subsequent step by the use of a zipper response, very like when shut an anorak. On this manner, along with the polymer with a single conjugated rail, the workforce obtained a polymer with two conjugated rails – the stiff “ladder”. Each polymers had been of equal size and will now be in contrast to one another: How would turning a snake right into a ladder have an effect on the fabric’s properties? The researchers examined the construction utilizing a scanning tunneling microscope. The tiny molecular ladder is one nanometer (a millionth of a millimeter) excessive, two nanometers extensive and 100 nanometers lengthy. The chemists additionally confirmed the form and extraordinary rigidity of the ladders – in comparison with the snakes – by way of in depth pc simulations utilizing a novel principle that predicts the person motions of all atoms throughout the molecule.

Pc simulation of the dynamics of a molecular “snake” and a “ladder”. The snake folds shortly whereas the ladder stays inflexible over the time of the simulation. (Video: Sebastian Spicher)

Potential constructing block for electronics

“The ladder construction is retained not solely when the molecules are positioned on a floor, but additionally when they’re dissolved in a liquid,” says Prof. Lupton of the College of Regensburg. This characteristic, he provides, permits vitality to maneuver alongside the molecule in area, offering a possible constructing block for optical networks, circuits and sensors. In precept, such polymers conduct electrical currents and can be utilized to make new shows based mostly on natural light-emitting diodes (OLEDs), or to transform mild into electrical energy in a photo voltaic cell. When mild falls onto such a molecule, it’s absorbed and produces a small packet of vitality. The researchers had been capable of observe how these packages moved alongside the ladder just about unimpeded, as if on a zipline. The open snake-like polymers, alternatively, don’t present this impact. Their properties are much like these of standard polymer molecules: the packages slide alongside the “snakes” and lose vitality.

Kekulé’s shattered dream

“Whereas previous Kekulé ‘noticed’ the only molecule as a hoop, he definitely by no means dreamed that there would someday be large molecules of such rigidity that they’re unable to chunk their very own tails,” says Höger, summarizing the outcome with a wink.