In
this work, we use density functional theory calculations with
a hybrid exchange–correlation functional and effective core
pseudopotentials to determine the geometry of bare and phosphine-protected
Au
8
nanoclusters and characterize their electronic structure.
Au
8
clusters were bonded to four and eight PH
3
ligands in order to evaluate the effect of ligand concentration
on the electronic structure, while different positional configurations
were also tried for four ligands attached to the cluster. We show
that the neutral clusters become more nucleophilic as the ligands
bind to the clusters at stable sites. The ground-state planar configuration
of Au
8
is maintained depending on the concentration and
position of ligands. The effect of ionizing to the +2 charge state
results in disruption of planar geometry in some cases because of
inoccupation of a molecular orbital with the Au–Au bonding
character. Natural bond order charge analyses showed that Au atoms
oxidize upon ionization, instead of phosphine. The net positive charge
makes the clusters more electrophilic with a capacity to absorb electrons
from nucleophiles depending on the concentration and position of ligands
and on the concentration of low-coordinated gold atoms. Besides, ionization
energies and electron affinities were calculated through different
mechanisms, finding that both variables are much higher for charged
systems and change inversely with the concentration of ligands.