Supramolecular dyads as photogenerated qubit candidates.

Molecular spin qubits have the advantages of synthetic flexibility and amenability to be tailored to specific applications. Among them, chromophore-radical systems have emerged as appealing qubit candidates. These systems can be initiated by light to form triplet-radical pairs that can result in the formation of quartet states by spin mixing. For a triplet-radical pair to undergo spin mixing, the molecular bridge joining the spin centres must permit effective spin communication, which has previously been ensured using covalent, π-conjugated linkers. Here we used perylenediimides and nitroxide radicals designed to self-assemble in solution via hydrogen bonding and observed, using electron paramagnetic resonance spectroscopy, the formation of quartet states that can be manipulated coherently using microwaves. This unprecedented finding that non-covalent bonds can enable spin mixing advances supramolecular chemistry as a valuable tool for exploring, developing and scaling up materials for quantum information science.