Hybrid Molecular Magnets with Lanthanide- and Countercation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate.

A series of {V}-nuclearity polyoxovanadate cages covalently functionalized with one or sandwiched by two phthalocyaninato (Pc) lanthanide (Ln) moieties V-O-Ln bonds were prepared and fully characterized for paramagnetic Ln = Sm-Er and diamagnetic Ln = Lu, including Y. The LnPc-functionalized {VO} cages with fully oxidized vanadium centers in the ground state were isolated as (BuN)[HVOCl(LnPc)] and (BuN)[HVOCl(LnPc)] compounds. As corroborated by a combined experimental (EPR, DC and AC SQUID, laser photolysis transient absorption spectroscopy, and electrochemistry) and computational (DFT, MD, and model Hamiltonian approach) methods, the compounds feature intra- and intermolecular electron transfer that is responsible for a partial reduction at V(3d) centers from V to V in the solid state and at high sample concentrations. The effects are generally Ln dependent and are clearly demonstrated for the (BuN)[HVOCl(LnPc)] representative with Ln = Lu or Dy. Intramolecular charge transfer takes place for Ln = Lu and occurs from a Pc ligand the Ln center to the {VO} core of the same molecule, whereas for Ln = Dy, only intermolecular charge transfer is allowed, which is realized from Pc in one molecule to the {VO} core of another molecule usually the BuN countercation. For all Ln but Dy, two of these phenomena may be present in different proportions. Besides, it is demonstrated that (BuN)[HVOCl(DyPc)] is a field-induced single molecule magnet with a maximal relaxation time of the order 10 s. The obtained results open up the way to further exploration and fine-tuning of these three modular molecular nanocomposites regarding tailoring and control of their Ln-dependent charge-separated states (induced by intramolecular transfer) and relaxation dynamics as well as of electron hopping between molecules. This should enable us to realize ultra-sensitive polyoxometalate powered quasi-superconductors, sensors, and data storage/processing materials for quantum technologies and neuromorphic computing.