Self-assembly of structurally rigid diamondoid esters on a HOPG surface

Characterizing assemblies of non-aromatic organic molecules on carrier surfaces is still an underexplored field of nanomaterial design. Here we present a study of on-surface self-assembly for diamondoid ester compounds on a highly oriented pyrolytic graphite (HOPG) surface. Using a combination of experimental and computational tools, we have developed an approach to characterize such non-aromatic molecules that also do not possess long alkyl chains in their structures. AFM imaging visualized the formed on-surface domains and by using the semi-empirical quantum mechanical GFN2-xTB method we could identify the most stable on-surface orientations of the individual molecules, a non-trivial task for non-aromatic compounds. Our synergistic analysis revealed that intermolecular London dispersion interactions enable molecular chains formation, which then arrange into distinct domains of observable structural periodicity. Our findings not only shed light onto self-assembly behavior of diamondoid esters but also provide a more general approach for characterizing currently less explored non-aromatics on carrier surfaces.