To provide an interpretation and computational support of the experimental absorption spectra (Figure ), we employed the CAM-B3LYP/aug-cc-pVTZ/Au(PP) density functional theory method. The equilibrium geometries were obtained at the PBE0/def2-TZVPP/PP(Au) level. This combination provided a good agreement between the computed and experimental data and afforded their straightforward interpretation. A comparison of the DFT functionals, basis set requirements, subtle structural effects on the computed spectra, as well and the spin-orbit effects are given in the SI, including the full set of the calibration data, Tables .