Structural Evolution of Carbon-Doped Aluminum Clusters AlnC- (n=6-15): Anion Photoelectron Spectroscopy and Theoretical Calculations

Carbon-doped aluminum cluster anions, AlnC- (n = 6-15), were generated by laser vaporization and investigated by mass-selected anion photoelectron spectroscopy. The geometric structures of AlnC- (n = 6-15) anions were determined by the comparison of theoretical calculations with the experimental results. It is found that the most stable structure of Al6C- is a carbon endohedral triangular prism. The Al7C- anion is a magic cluster with high stability. The structures of Al7-9C- can be viewed as the additional aluminum atoms attached around the triangular prism Al6C-. Two isomers of Al10C- have been detected in the experiments. The most stable one has a planar tetracoordinate carbon structure. The second one derives from Al9C- with the carbon atom located in a pentagonal bipyramid. The Al11C- anion has a bilayer structure composed of one planar tetracoordinate carbon and one aluminum-centered hexagon, in which the major interactions between two layers are multicenter bonds. The structures of Al12-14C- can be viewed as evolving from Al11C- by adding aluminum atoms to interact with the carbon atom. In Al15C-, the carbon atom stays at the surface with a tetracoordinate structure, and an icosahedral Al-13 unit can be identified as a part of the geometric structure of Al15C-.

Automated summary

The geometric structures of AlnC- (n = 6-15) anions were determined by mass-selected anion photoelectron spectroscopy. The most stable structure of Al6C- is a carbon endohedral triangular prism, while Al7C- is a magic cluster with high stability. The structures of Al7-9C- can be viewed as aluminum atoms attached around Al6C-.