Vanadyl Porphyrin Complex Functionalized with Nitronyl Nitroxide

The development of effective frameworks for coupling chemically synthesized qubits is essential for advancing molecular quantum technologies. Vanadium(IV) (VO) magnetic centers are promising candidates for molecular quantum units. To create a novel type of two-qubit vanadyl-containing system, we synthesized and fully characterized the first vanadyl porphyrin derivative featuring a conjugated nitronyl nitroxide radical (VO(Por)-NN). Using X-ray diffraction (XRD), we determined the molecular and crystal structures of the solvate complex, VO(Por)-NN·n(CH2Cl2). When dissolved in dichloromethane, this solvate complex produces an electron paramagnetic resonance (EPR) spectrum that is a superposition of two distinct signals: the spectrum of the monomeric VO(Por)-NN complex, in which the paramagnetic centers (vanadyl and nitronyl nitroxide) do not interact; and the spectrum of the dimeric {VO(Por)-NN}2 species, in which exchange interactions between the spins are observed. Desolvation of a polycrystalline sample triggers its complete conversion into the dimeric form {VO(Por)-NN}2, thereby activating exchange interactions between the vanadyl and nitroxide spins. To the best of our knowledge, such self-organization of spin systems involving a vanadyl center and an organic radical has not been observed previously. It represents a novel supramolecular approach to the construction of multispin clusters.