CAl11−: a molecular rotor with a quasi-planar tetracoordinate carbon.

In this work, we analyzed the bonding and fluxional character of the global minimum of CAl11−. Its structure is formed by two stacked layers, one of them resembles the well-known planar tetracoordinate carbon CAl4 on top of a hexagonal Al@Al6 wheel. Our results show that the CAl4 fragment rotates freely around the central axis. The exceptional stability and fluxionality of CAl11− derive from its particular electron distribution. [ABSTRACT FROM AUTHOR]