Authors: Irina Werner | Jan Griebel | Albert Masip‐Sánchez | Xavier López | Karol Załęski | Piotr Kozłowski | Axel Kahnt | Martin Boerner | Ziyan Warneke | Jonas Warneke | Kirill Yu. Monakhov
Source: Inorganic Chemistry (article, 2022-12-19)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Hybrid Molecular Magnets with Lanthanide- and Countercation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate A series of {V<sub>12</sub>}-nuclearity polyoxovanadate cages covalently functionalized with one or sandwiched by two phthalocyaninato (Pc) lanthanide (Ln) moieties <i>via</i> V-O-Ln bonds were prepared and fully characterized for paramagnetic Ln = Sm<sup>III</sup>-Er<sup>III</sup> and diamagnetic Ln = Lu<sup>III</sup>, including Y<sup>III</sup>. The LnPc-functionalized {V<sub>12</sub>O<sub>32</sub>} cages with fully oxidized vanadium centers in the ground state were isolated as (<i>n</i>Bu<sub>4</sub>N)<sub>3</sub>[HV<sub>12</sub>O<sub>32</sub>Cl(LnPc)] and (<i>n</i>Bu<sub>4</sub>N)<sub>2</sub>[HV<sub>12</sub>O<sub>32</sub>Cl(LnPc)<sub>2</sub>] 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<sup>V</sup> to V<sup>IV</sup> in the solid state and at high sample concentrations. The effects are generally Ln dependent and are clearly demonstrated for the (<i>n</i>Bu<sub>4</sub>N)<sub>3</sub>[HV<sub>12</sub>O<sub>32</sub>Cl(LnPc)] representative with Ln = Lu<sup>III</sup> or Dy<sup>III</sup>. Intramolecular charge transfer takes place for Ln = Lu<sup>III</sup> and occurs from a Pc ligand <i>via</i> the Ln center to the {V<sub>12</sub>O<sub>32</sub>} core of the same molecule, whereas for Ln = Dy<sup>III</sup>, only intermolecular charge transfer is allowed, which is realized from Pc in one molecule to the {V<sub>12</sub>O<sub>32</sub>} core of another molecule usually <i>via</i> the <i>n</i>Bu<sub>4</sub>N<sup>+</sup> countercation. For all Ln but Dy<sup>III</sup>, two of these phenomena may be present in different proportions. Besides, it is demonstrated that (<i>n</i>Bu<sub>4</sub>N)<sub>3</sub>[HV<sub>12</sub>O<sub>32</sub>Cl(DyPc)] is a field-induced single molecule magnet with a maximal relaxation time of the order 10<sup>-3</sup> 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. Chemistry ; Lanthanide ; Intramolecular force ; Intermolecular force ; Electron paramagnetic resonance ; Molecule ; Crystallography ; Single-molecule magnet ; Phthalocyanine ; Electron transfer ; Paramagnetism ; Polyoxometalate ; Physical chemistry ; Ion ; Stereochemistry ; Nuclear magnetic resonance ; Magnetization Magnetism in coordination complexes ; Polyoxometalates: Synthesis and Applications ; Porphyrin and Phthalocyanine Chemistry