  We present the first experimental investigation of the effect of increased
isotropic pressure on the superatomic electronic structure of metal
nanoclusters in the molecular state. Broad multiband absorbing
[Ag44(SPhCOOH)30]4-, [Ag44(SPhF2)30]4- & [Ag25(SPhMe2)18]- nanoclusters were
optically examined up to 200 MPa, revealing a reversible change to the
superatomic electronic structure. Deviations from the ambient spectra became
significant above 50 MPa, revealing both red and blue shifts to spectral
features. Comparison of the spectral peaks to calculated electronic transitions
indicate that electronic states on the ligand are destabilized and that the
splitting of the superatomic orbitals decreases with increasing pressure. These
findings highlight that under relatively modest pressure the fundamental
superatomic electronic structure of metal nanoclusters can be manipulated, thus
the optical and electronic properties of functional materials containing
nanoclusters such as in solar cells and photocatalytic devices can be tuned by
the application of pressure.
