Unusual Solvent Effects on Optical Properties of Bi-Icosahedral Au25 Clusters

Abstract

Temperature-dependent and time-resolved absorption measurements were carried out to understand the influence of solvent hydrogen bonding on the optical properties of bi-icosahedral [Au25(PPh3)10(C6S)5Cl2]2+ (bi-Au25) clusters. Theoretical calculations have shown a low energy absorption maximum that is dominated by the coupling of the two Au13 icosahedra, as well as a high energy absorption arising from the individual Au13 icosahedra that make up the bi-Au25 clusters. Temperature-dependent absorption measurements were carried out on bi-Au25 in aprotic (toluene) and protic (ethanol and 2-butanol) solvents to elucidate the cluster–solvent hydrogen bonding interactions. In toluene, both the low and high energy absorption bands shift to higher energies consistent with electron–phonon interactions. However, in the protic solvents, the low energy absorption shows a zigzag trend with decreasing temperature. In contrast, the high energy absorption in protic solvents shifts monotonically to higher energy similar to...