Tuning the electronic structure of gold cluster-assembled materials by altering organophosphine ligands.

Superatomic clusters can be assembled to build bulk matter, where the individual characteristics are preserved. The main benefit of these materials over conventional bulk species is the capability to tailor their features by altering the physicochemical identities of individual clusters. Electronic properties of metal clusters can be modified by a protective shell of ligands that attach to the surface and make the whole nanoparticle soluble in organic or aqueous solvents. In the present work, we demonstrate that properly chosen ligands provide not only steric protection from aggregation but also tune the redox activity of metal clusters. We investigate the role of the ligands in electronic structure tunability and ligand-field splitting. Our first-principles calculations agree with the experiments, showing that phosphine-protected gold materials are small gap semiconductors. The obtained bandgaps strongly depend on the ligand used. Hence, using phosphine and organophosphine ligands should be feasible and promising while designing the novel superatom-based materials since the desired range of the bandgap might be achieved (by the proper choice of the ligand).