Enhanced Coherence by Coupling Spins through a Delocalized π-System: Vanadyl Porphyrin Dimers

Vanadium(IV) magnetic centers are prime candidates as molecular quantum units. One longstanding question is how to obtain a scaffold that connects multiple centers and allows two communication modalities: magnetic and electronic. We have synthesized and studied a selection of vanadyl porphyrin dimers, as models of the most synthetically accessible linear porphyrin arrays. We show that a strongly π-conjugated backbone places the magnetic system in the strong coupling regime and protects the quantum coherence against electron pair flip-flop processes at low temperatures (<10 K). This result is a fundamental step towards the design of molecular materials for single-molecule devices controlled by microwaves with electrical readout.