By using Ab initio approach, we have analysed Silicene-, Germaneneand Graphene-based molecular single-electron transistors. It is based on non-equilibrium greens function (NGEF) and density functional theory (DFT). Three different fullerene molecules are taken and optimization is done. In Coulomb blockade regime, silicene, germanene and graphene are kept above gate dielectric between drain and source for weak coupling. We have taken gold electrodes for SET environment. Gold is widely used as metal electrode in nanoscale devices. We have calculated the HOMO and LUMO values and total energy versus gate voltage. Charge stability diagrams are obtained by calculating charging energy as function of external gate potential. By these calculations, the analysis of three different molecular single-electron transistors is done. The total energies of these molecules are highly negative (very low) compared to other molecules.