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Optical Properties of Small Gold Clusters Au8L82+ (L = PH3, PPh3): Magnetic Circular Dichroism Spectra

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journal contribution
posted on 02.08.2017, 00:00 by Natalia V. Karimova, Christine M. Aikens
A theoretical study of the optical and electronic properties of small phosphine-protected centered gold clusters with gold core symmetry C3v was performed using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. It is well-known that magnetic circular dichroism (MCD) spectroscopy yields more detailed information about electronic structure and optical properties with respect to optical absorption spectroscopy. In this work, we combine electronic absorption and MCD spectroscopy for gold nanoclusters to gain a better understanding of their electronic states. These results can be used to help with interpretation of the experimentally measured MCD spectra, which is a very complicated process, especially for low-symmetry systems. In the present paper, absorption and MCD spectra were calculated for ligand-protected gold clusters Au8(PPh3)82+ and Au8(PH3)82+, in addition to bare Au82+. The influence of the nature of the ligands on the optical properties of gold cluster was investigated. Geometrical changes and changes in optical properties that occur in the Au8 gold core during the ligation process were also determined. A comparative analysis of the obtained theoretical and experimental results was performed. The results show that the theoretically simulated optical absorption and MCD spectra for Au8(PPh3)82+ exhibit a very good agreement with empirical spectra for [Au8(PPh3)8]­(NO3)2 in acetonitrile.