No 'electron dancing' allowed in new molecular design rules

For over a century, scientists have been aware of the coupling between electrons and atomic motion in in molecules and molecular design, a phenomenon discovered alongside quantum mechanics.

These molecular vibrations, resembling tiny springs, cause electrons to dance to the rhythm of the atoms on incredibly short timescales — a mere millionth of a billionth of a second.

Researchers from the Cavendish Laboratory at the University of Cambridge, led by Professor Akshay Rao, have recently reported groundbreaking findings in the journal Nature.

Pratyush Ghosh, a PhD student at the Cavendish Laboratory and a member of St John’s College, is the first author of the study.

Impact of electron-vibration coupling

The constant motion of electrons, caused by their coupling with atomic vibrations, leads to energy loss and limits the performance of organic molecules in various applications.

These include light-emitting diodes (OLEDs), infrared sensors, and fluorescent biomarkers used in cell studies and disease tagging, such as identifying cancer cells.

“All organic molecules, such as those found in living cells or within the screen of your phone consist of carbon atoms connected to each other via a chemical bond,” explained Ghosh.

“Those chemical bonds are like tiny vibrating springs, which are generally felt by electrons, impairing the performance of molecules and devices,” he concluded.

Discovering new molecular design rules

Using laser-based spectroscopic techniques, the researchers discovered ‘new molecular design rules’ that can effectively halt the molecular dance between electrons and atomic vibrations.

By restricting the geometric and electronic structure of molecules to specific configurations, the scientists found that certain molecules can avoid the detrimental effects of electron-vibration coupling.

To demonstrate these design principles, the researchers designed a series of efficient near-infrared emitting (680-800 nm) molecules.

In these molecules, energy losses resulting from vibrations were more than 100 times lower than in previous organic molecules.

“However, we have now found that certain molecules can avoid these detrimental effects when we restrict the geometric and electronic structure of the molecule to some special configurations,” added Ghosh.

Future applications and implications

The understanding and development of these new rules for designing light-emitting molecules have opened up an exciting trajectory for the future.

These fundamental observations can be applied to various industries, potentially leading to enhanced displays and improved molecules for biomedical imaging and disease detection.

“These molecules also have a wide range of applications today. The task now is to translate our discovery to make better technologies, from enhanced displays to improved molecules for bio-medical imaging and disease detection,” concluded Professor Rao.

Focusing on peak performance in molecular design

In summary, the discovery of new molecular design rules by researchers at the Cavendish Laboratory opens up a world of possibilities for the future of organic molecules and their applications.

By understanding and applying these principles, scientists can now design molecules that avoid the detrimental effects of electron-vibration coupling, leading to significantly improved performance and efficiency.

This research highlights a new path for the development of enhanced technologies, from advanced displays to innovative biomedical imaging and disease detection methods.

As researchers continue to explore and refine these design rules, we can expect to see a quantum leap forward in the capabilities of organic molecules, revolutionizing industries and improving our daily lives.

The full study was published in the journal Nature.

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