Non-Covalent Interactions Enable Efficient Spin Communication in Molecular Spin Qubits

A Franco-German research collaboration, involving teams from the University of Freiburg and the University of Strasbourg’s Institut Charles Sadron, has made a breakthrough in the development of molecular spinqubits for quantum technologies. Their findings, published in Nature Chemistry, reveal that supramolecular chemistry can facilitate efficient spin communication via hydrogen bonds—an approach that could greatly accelerate the materialization of quantum technologies, particularly in quantum sensing and molecular spintronics.

Quantum Bits: The Quest for the Right Material

Quantum computing relies on qubits, the fundamental units of quantum information. Unlike classical bits that exist in one state (either 0 or 1), qubits exploit the principles of quantum mechanics, existing in multiple states simultaneously. However, a major challenge in quantum technology is identifying the right material to construct these qubits in practical, scalable, and efficient ways.

Molecular spin qubits are considered promising candidates, particularly for applications in molecular spintronics, where spin—rather than electrical charge—is used to encode and manipulate information. These spin qubits can also be used for quantum sensing, making them valuable for numerous advanced applications. However, a significant hurdle has been how to manipulate the interaction between the spins effectively.

The Role of Hydrogen Bonds in Spin Communication

For successful quantum applications, efficient communication between multiple spin centers is essential. Early research into molecular spinqubits assumed that a strong spin-spin interaction, necessary for producing a stable quartet spin state, could only be achieved if the spin centers were covalently linked—that is, chemically bonded in such a way that they share electrons and form strong, stable structures.

Yet, synthesizing such covalently linked networks is labor-intensive, costly, and difficult to scale. This made covalent structures less feasible for practical applications in quantum technologies. This limitation prompted researchers to look for non-covalent ways to achieve efficient spin communication while maintaining the ease and scalability needed for real-world applications.

The Breakthrough: Supramolecular Chemistry

The research team led by Sabine Richert at the University of Freiburg and colleagues from the University of Strasbourg has made a pioneering discovery in this regard. Their study shows, for the first time, that non-covalent interactions—specifically hydrogen bonds—can enable efficient spin communication. By using a model system composed of perylenediimide (a chromophore) and nitroxide radicals (spin centers), the team demonstrated that these units can self-assemble into functional structures in a solution through hydrogen bonds.

This approach leverages supramolecular chemistry, which focuses on the non-covalent interactions between molecules, such as hydrogen bonding, van der Waals forces, and π–π stacking. In this case, these interactions were used to control the spatial and electronic arrangement of the spin centers, allowing the researchers to achieve the efficient communication between spins needed to form the light-induced quartet state.

Advantages of Supramolecular Approaches

The key advantage of this breakthrough is that supramolecular chemistry opens the door to scalable and efficient systems without needing complex and resource-intensive covalent bond synthesis. The team was able to construct an ordered network of molecular spin qubits using non-covalent interactions, which drastically simplifies the creation of large, intricate spin networks.

This is a significant step forward because it allows the creation of complex spin systems in a solution, without the need for extensive synthetic modification of each new molecule. The research now enables the combination of different molecules in spin networks, helping to expand the possibilities for quantum materials and enhancing the ability to test different systems efficiently.

Furthermore, the ability to scale these systems could help make quantum technologies more practical and accessible. With this approach, large networks of spinqubits could be created and optimized more rapidly—thus addressing one of the key scalability problems in quantum technology development.

Future Potential in Quantum Technology

The results from this study highlight the immense potential of supramolecular chemistry to contribute to the field of quantum research and molecular spintronics. This method lays the groundwork for producing complex materials that are capable of scaling up for practical use. With these new insights, researchers can now test and optimize different molecule combinations to further enhance qubit coherence and system stability.

“The findings are an important step toward developing new components for molecular spintronics,” says Sabine Richert, who directs the Emmy Noether junior research group at the University of Freiburg’s Institute of Physical Chemistry. This work could enable the creation of more effective, scalable materials, which in turn could accelerate the development of quantum technology.

Implications for the Field of Spintronics

While this research does not directly contribute to the final realization of large-scale quantum computing, it opens up vital avenues for advancing molecular spintronics. Spintronics—an emerging field where electron spin is used in information storage and processing—has significant overlap with quantum computing, especially as both areas explore the role of quantum states in information processing.

One potential application of these supramolecular spin networks is quantum sensing, where the sensitivity of spin states can be used to detect extremely small changes in a physical environment. This could lead to the development of precision measurement tools for a variety of industries, from materials science to medical imaging.

Moreover, the flexibility inherent in supramolecular chemistry may allow for the rapid prototyping of new molecular designs. This could mean faster iterations of materials with tailored properties that are tuned specifically to meet the needs of quantum information technologies.

Conclusion

In conclusion, the findings by the Franco-German research team from the University of Freiburg and the University of Strasbourg mark a transformative shift in our understanding of molecular spinqubits. By demonstrating that hydrogen bonds and supramolecular interactions can facilitate effective spin communication, they open up new paths for the development of efficient, scalable quantum devices. These insights provide both practical solutions and new theoretical approaches to the ever-present challenge of creating suitable materials for quantum information processing, bringing us one step closer to the future of molecular spintronics. As the field continues to evolve, these advances could help unlock the next generation of quantum sensors, memory devices, and computing technologies.

Reference: Ivan V. Khariushin et al, Supramolecular dyads as photogenerated qubit candidates, Nature Chemistry (2025). DOI: 10.1038/s41557-024-01716-5