Molecular models. Density functional theory (DFT) at the ωB97X-D/6-311++G(d,p) level of theory was used for molecular modeling as described in Methods. Energy profiles of the cleavage of inert C -H bonds in methane molecule were first calculated for a series of substituted gallium imide structures shown in Figure . Perfluorophenyl (C 6 F 5 ) was used as an electron-withdrawing group (EWG), trimethylsilyl (TMS) as a σ electron donating group (EDG), while phenyl was considered as a neutral group. The gallium imide proposed by Nikonov et al. was represented by R 1 --Ph and R 2 --TMS. In the next step, the struc- ture of the most promising imide was adjusted to improve its methane activation efficiency further.