Quantum Chemical Insight into LaC: Metal Carbide Fullerene LaC@C versus Dimetallofullerene La@C.

A family of dilanthanum-containing endohedral metallofullerene LaC (n = 46-51) was synthesized recently. In the present work, a systematical investigation on LaC series including the carbide clusterfullerene form LaC@C and the conventional dimetallofullerene form La@C was implemented by density functional theory, combined with statistical mechanics. Three isomers, i.e., La@D(191838)-C, LaC@C(153479)-C, and LaC@C(153491)-C were disclosed to be thermodynamically stable at the temperature region of endohedral metallofullerene formation. La@D(191838)-C is the prevailing isomer at low temperature, while LaC@C(153479)-C and LaC@C(153491)-C are the most and second-most abundant isomers at high temperature. Interestingly, the highest occupied molecular orbital (HOMO) of LaC@C(153491)-C is distributed on one pole of the cage, and the lowest unoccupied molecular orbital (LUMO) of this isomer is mainly located on the equator of the cage, which can facilitate synthesis of regioselective derivatives. This work will provide useful information for further experimental identification and application of LaC.