Enhanced coherence by coupling spins through a delocalized -system: Vanadyl porphyrin dimers

Vanadium(IV) magnetic centers are prime candidates for molecular quantum units. One long-standing 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 pi -conjugated backbone places the magnetic system in an intermediate regime dominated by exchange coupling (J) and protects the quantum coherence against electron pair flip-flop processes at low temperatures (<10 K). This result is a fundamental step toward the design of molecular materials for single -molecule devices controlled by microwaves with electrical readout.