Toward Polyoxometalate Nanoelectronics.

Polyoxometalates form a large family of molecular oxide clusters of the early transition metals with unique and tunable properties (multiredox, thermal and chemical robustness, magnetic). We review more than 30 years of experimental research on the electron transport properties of polyoxometalate devices, from thin films and self-assembled monolayers down to single-molecule junctions. We focus on the relationship between the polyoxometalate structures (structural type, nature of metals and heteroatoms, role of the counterions, redox states, electrode linkers, and functional ligands) and the electronic structures of the polyoxometalate-based devices (energy positions of the molecular orbitals, energy offset at the interfaces). Then, we critically discuss the performances of polyoxometalates in nanoelectronic devices: capacitance and resistive switching memories, spintronics, quantum bits, and neuromorphic devices. We conclude with a discussion of pending issues and perspectives.