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Modelling of Architectures Ruled by Coupled or Heightened Excited States

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More efficient ‘multi-switchable’ molecules could boost data storage

EU scientists can now model how complex molecules switch from one state to another when exposed to light, potentially paving the way for more efficient data storage devices and other novel technologies.

Fundamental Research

Photochromes – or molecules that can exist in two forms – can be switched from one form to another by being exposed to light. They are used for a wide range of purposes from colour-changing sunglasses to data storage. Scientists are now working on how to increase the potential of photochromes by improving their switching possibilities. EU-funded project MARCHES (Modelling of Architectures Ruled by Coupled or Heightened Excited States) has laid the foundations for more efficient ‘multi-photochromes’. These are molecules that combine several switchable units onto the same molecule core, potentially boosting the amount of data one molecule could contain from one bit of information to one byte or more. ‘Under current technology, most compounds with two or more molecular switches are inefficient – usually only one of their switches works properly. Our main goal was to design improved multi-switchable molecules using chemical-modelling tools, in particular Time-Dependent Density Functional Theory, a quantum theory. These molecules could then pave the way towards more complex and efficient devices,’ explains Denis Jacquemin, MARCHES project coordinator. Throughout the project, scientists developed new molecule modelling techniques that could quantify the interactions between the different photochromes inside a molecule. This allowed them to discover the physics behind the current limitations of multi-photochrome molecules. ‘The challenge MARCHES set itself was particularly high since the switching processes are induced by light and therefore require the calculations of many coupled electronically excited states. However, we succeeded in establishing a series of new complementary models for several scenarios and we obtained results that matched the experiments,’ says Jacquemin. These models can now be used to design more efficient photochromes which could later be used in more efficient data storage devices or other technology sectors like photochromic colour-changing objects showing more than two colours, novelty toys and clothing. MARCHES has also led to other results, including three new patents in alternative cycles to porphyrins for optical applications like solar cells, materials able to generate white-light for new lighting devices, and photo-responsive paper with hidden marks which could find applications in packaging. With the project now over, researchers have moved on to exploring fluorescent dyes that could be used for medical applications, as well as to the semi-quantitative prediction of reaction yields at excited-states. This will allow more accurate theoretical predictions that could advance experiments in creating better fluorescent molecules. ‘Researchers have made some exciting progress in model compounds, and we believe that applications in real-life systems, such as improved lightning devices, are now definitely within reach,’ concludes Jacquemin.


MARCHES, switchable molecules, florescent markings, lighting, sunglasses, packaging

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