EPSRC-Chemistry (CHE) Synthetic Molecular Compasses

Synthetic Molecular Compasses for Optical Read-Out of the Strength and Direction of the Earth’s Magnetic Field Context: Many animals, including night-migratory songbirds, navigate using the Earth’s magnetic field. Although the mechanisms are not fully understood, mounting evidence points to Nature employing coherently driven quantum processes to detect magnetic interactions a million times weaker than the thermal energy in biological tissue. According to this quantum hypothesis of animal magnetoreception, blue light photoexcitation of a protein (cryptochrome) in the retinae of animals’ eyes generates short-lived radicals whose reaction yields and rates are sensitive to the direction and strength of ambient magnetic fields. Despite the exceptional field sensitivity of this biological compass, which operates within the “wet and noisy” environment of a cell, very few synthetic chemical compasses have been explored in chemistry laboratories. Challenge the project addresses: Only a single synthetic chemical compass has so far been demonstrated for Earth-strength magnetic fields. We will use a collaborative approach to design a family of bespoke, high sensitivity chemical compasses. We will combine symbiotically the power of chemical synthesis, which offers infinite flexibility in molecular design, with our unique suite of state-of-the art spectroscopies and our powerful quantum mechanical techniques to explore the compasses’ spin dynamics and refine their magnetosensitivity. Aims and objectives: We will investigate the response to magnetic fields of two types of photo-generated spin-correlated pairs: (a) doublet pairs in molecular donor-bridge-acceptor (D-B-A) triads, and (b) triplet pairs produced by singlet fission in polyacene single crystals. In both systems, we seek to develop strategies to optimise the sensitivity of the compass to magnetic fields by perfecting their molecular structure through chemical synthesis and engineering of materials. In parallel, we aim to elucidate molecular structure-property relationships through theoretical simulation. All systems will be characterised using a combination of sensitive optical techniques, magnetometry and electron spin resonance spectroscopy. We plan to create synthetic molecular compasses with field sensitive optical read-outs (such as in singlet fission or via field-sensitive phosphorescing triplet recombination products). Potential applications and benefits: This project will generate fundamental insight into the control of quantum dynamics in molecular systems. It will enhance our insights into the operation of biological magnetoreceptors, and thus contribute to the debate about how animals detect magnetic fields. We will establish design principles for artificial quantum compasses capable of sensitive detection of both the magnitude and direction of weak magnetic fields, with applications in quantum sensing, quantum navigation and magnetogenetics. A major benefit of this project will be to establish a long-term collaboration between Oxford and Northwestern Universities, with their complementary world-leading expertise including synthesis, spectroscopy, spin dynamics and theory.