Symmetry controlled adsorption of di-iodobenzene on MoS₂

In a joint experimental and theoretical study, we have uncovered evidence of the importance of symmetry in the adsorption of the isomers of di-iodobenzene on MoS₂(0001). The intensity ratio of iodine to molybdenum measured, as a function of exposure for different isomers of the di-iodobenzene, show that while for ortho (1,2-) and para (1,4-) di-iodobenzene the rate of adsorption at 100 K is very low, that for meta (1,3-)di-iodobenzene is considerably more facile. We have applied van der Waals corrected density functional theory based calculations to understand the subtleties in the electronic structure and geometry of adsorption of these three di-iodobenzene isomers on MoS₂(0001). All three are found to weakly chemisorb onto MoS₂(0001) with the same binding strength as well as adopt similar configurations. The calculated electron affinity of the three molecules also do not show a specific trend that would verify experimental data. However analysis of the frontier orbitals indicate that those of 1,3-di-iodobenzene is strongly affected by interactions with MoS₂, while that of the other two isomers remain unchanged. Our results show that symmetry is the identifying factor in the adsorption characteristics of di-iodobenzene on MoS₂.