Optical Spectra of the Special Au144 Gold-Cluster Compounds: Sensitivity to Structure and Symmetry

This report concerns the remarkable fine structure reported recently in the optical absorption spectrum of the ubiquitous icosahedral Au144(SR)60 cluster compounds when measured under cryogenic conditions. The theoretical explanation of the spectrum relied upon an I-symmetrized variant of the conventional Pd145-type structure-model; real-time TDDFT calculations revealed that, in contradistinction to the prior state of knowledge, the spectrum is profoundly structured and rich in quantum-state information.1 Reported herein is an investigation of the sensitivity of the theoretical electronic absorption spectra of this compound to variations in the structure. Both I-symmetric as well as asymmetric structure-models are considered; having the same core structure and connectivity, these differ in the mutual configurations about the pyramidal S atoms, which produce significant structure differences penetrating into the gold core. As R-groups, both methyl (R=CH3) and hydrogen (R=H) are considered. The effects on t...