Nano-jewellery: C5Au12—a gold-plated diamond at molecular level
A mixed carbon-metal cluster is designed by combining the tetrahedral C5 radical (with a central atom—the skeleton of the C5H12 molecule) and the spherical Au12 layer (the external atomic shell of the Au13 cluster). The C5Au12 cluster and its negative and positive ionic derivatives, C5Au12±, are investigated ab initio (DFT) in terms of optimized structures and relative energies of a few spin-states, for the icosahedral-like and octahedral-like isomers. The cluster is predicted to be generally more stable in its octahedral shape (similar to C5H12) which prevails for the negative ion and may compete with the icosahedral shape for the neutral system and positive ion. Adiabatic ionization energies (AIE) and electron affinities (AEA) of C5Au12, vertical electron-detachment (VDE) energies of C5Au12−, and vertical ionization and electron-attachment energies (VIE, VEA) of C5Au12 are calculated as well, and compared with those for the corresponding isomers of the Au13 cluster. The AIE and VIE values are found to be close for the two systems, while the AEA and VDE values are significantly reduced for the radical-based species. A simple fragment-based model is proposed for the decomposition of the total interaction into carbon–gold and gold–gold components.