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@Al-6 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.