Tuning chemistry with light

University of Groningen scientists have made a catalyst with a light-operated switch. This allows them to use an external stimulus to change the end product of the catalyzed reaction. The proof of principle, which was published in Nature Communications on 24 March, could be used in a wide range of systems.

The scientists, led by Professor of Organic Chemistry Ben Feringa, fitted a metal-containing organic catalyst with a light-driven molecular motor. The catalyst they worked on has a metal core (Palladium) and bisphosphine ligands. The shape of the ligands determines the end product of the catalyzed process. The process can result in two chiral structures, mirror images of each other. Chirality is very important, especially in the pharmaceutical industry. Scientists are therefore working hard to gain control of the chiral structure.

‘We made a bisphosphine ligand in which we inserted a light-driven molecular motor’, Feringa explains. The light can switch the ligand and thereby change the chirality of the end product of the catalyst. It is not the first switchable catalyst his group has made: in March 2011 he published the design of a motor-driven catalyst in Science. ‘But that was a type of catalyst that isn’t used as much as the organometallic compounds.’

The new paper is an important proof of principle: ‘These types of catalysts are widely used in industry, so being able to control them with just an external stimulus is important.’ It may lead to the design of all sorts of new catalysts that can produce different end products in a controlled fashion. ‘In fact, we can already switch the catalyst to three different positions.’ But it will take some effort to come up with new, switchable catalysts. ‘You often can’t predict how exactly a modified catalyst will work. So the design is still part science, part art.’

Reference: Depeng Zhao, Thomas M. Neubauer & Ben L. Feringa. Dynamic control of chirality in phosphine ligands for enantioselective catalysis, Nature Communications 6, doi:10.1038/ncomms7652

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