Density functional calculation of the molecular properties of the [Au20-C60-Au20]n− (n = 0, 1, 2, 3) model complexes

Abstract

We have calculated molecular geometries, HOMO-LUMO gaps, Fermi levels and vibrational frequencies for the σ-linear, σ-bent and π-coordinated [Au20-C60-Au20]n− (n = 0–3) complexes using the density functional B3LYP method and LANL2DZ basis sets. Our calculations showed that the σ-bent η1(b)-[Au20-C60-Au20]3− complex is the global minimum structure with Au-C distances of 2.27 and 2.97 Å, respectively. The C60 calculated bouncing frequencies for the [Au20-C60-Au20]n− (n = 0–3) complexes appear at 18–60 cm−1 and compare well with the experimental value of 40 cm−1. The calculations of Mulliken charges indicate that the electrostatic interaction of the C60n− ions with the Au20 clusters plays a major role in the stability and electron-conducting properties of the [Au20-C60-Au20]n− (n = 0–3) complexes. The orbital analysis and calculated Fermi levels of the complexes indicate that the neutrally-charged singlet [Au20-C60-Au20] complexes have the HOMO-1 and LUMO+1 delocalized orbitals with Fermi levels at −5.18 eV that line up with the free C60 Fermi level.