Electrochemical and spectroelectrochemical investigation of the chemical, structural and electronic properties of molecular metal carbonyl nanoclusters

Electrochemical and spectroelectrochemical (SEC) techniques are widely employed in inorganic, coordination and organometallic chemistry. Nanoelectrochemistry and, in particular, the electrochemical study of atomically precise ligand protected metal nanoclusters has received great interest in the last decade. Molecular metal carbonyl clusters (MMCCs) are low valent atomically precise nanoclusters protected on the surface by a layer of CO ligands. Their metal cores may comprise from a few to some tens of metal atoms. Several electrochemical and SEC methods may be employed to study the redox properties of MMCCs. The reversible redox activity of MMCCs may originate from ad hoc conditions, in the case of lower nuclearity clusters, or incipient metallization of their metal core, as their sizes increase. Besides supplying information on the electronic and redox properties of MMCCs, electrochemical and SEC studies, supported by chemical, structural and computational investigation, can shed light on the structural changes induced by redox reactions of MMCCs. Moreover, the redox properties of MMCCs may be tuned by tailored chemical modifications. As a bonus, electrochemistry may be used to indirectly proof the hydride nature of larger MMCCs. Further information on the chemical properties of MMCCs may be gathered combining electrochemical, SEC, chemical, spectroscopic, structural and computational studies. This review will cover these different aspects of the electrochemical investigation of MMCCs, by exploring general principles and representative examples.