Just like a bicycle pedal that can be pushed forwards and backwards — this is how the new molecular switch can be described which Dr. Saeed Amirjalayer, a researcher in the field of nanotechnology at the University of Münster, and his co-authors from the Universities of Murcia (Spain) and Amsterdam (Netherlands) have now presented in the journal Angewandte Chemie International Edition. The pedal motion is triggered by light. What is special in this particular case is that, in contrast to similar molecular switches, the “pedal molecule” needs much less space to work.

Molecular switches are molecules which reversibly interconvert between two or more states and thereby control molecular processes. In living organisms, for example, such switches are necessary for muscle contraction. Researchers hope that by means of molecular switches they will be able to regulate molecular processes — for example, a controlled release of drugs from nano-capsules.

“Most of the so-far developed molecular units need a relatively large volume to switch,” explains Saeed Amirjalayer, who works at the Physics Institute and at the Center for Nanotechnology (CeNTech). He cites as an example the molecular rotors developed by the Dutch chemist Prof. Ben Feringa, for which, along with two other researchers, Feringa was awarded the Nobel Prize for Chemistry in 2016. For many applications, however — for example, molecular computers or catalysis — the molecular switches have to be embedded in polymers or crystals. Because of limitations of available space, large structural changes are not possible in these cases.

The researchers studied the “pedalo motion” using time-resolved Infrared spectroscopy. “For the development and application of photo-responsive molecular switches,” says Amirjalayer, “it is crucial to know not only the two ‘resting states’ but also the motion between them.”

Using this spectroscopic method, the researchers made “snapshots”, in extremely short time intervals, of the molecular switch after it had been activated by light. Combined with quantum chemical calculations, they arrived at a detailed picture of the operation mechanism.

For his research, Amirjalayer received funding from the German National Academy of Sciences Leopoldina.

Source: University of Münster