eV. We hypothesized that the lower energy peak was the result of a second isomer, induced by steric hindrance of the bulkier meta-P(Ph-OMe) 3 ligands. This isomerization has been shown to happen, for example in para-P(Ph-OMe) 3 -protected Au 9 clusters. We confirmed this hypothesis using two-laser double resonance experiments, as outlined in the Supplemental Information, and thus disregard the 1.9 eV peak for this analysis. We note that, even if the true HOMO-LUMO transition energy were the 1.9 eV peak, the data would still significantly deviate from the trend for para-substituted clusters, and thus the conclusions of this work would be unaffected. the charge of the cluster core in amplifying the ligand effect.