Identical Binding Energies and Work Functions for Distinct Adsorption Structures: Olympicenes on the Cu(111) Surface

Reliability is one of the major concerns and challenges in designing organic/inorganic interfaces for (opto)­electronic applications. Even small structural differences for molecules on substrates can result in a significant variation in the interface functionality, due to the strong correlation between geometry, stability, and electronic structure. Here, we employed state-of-the-art first-principles calculations with van der Waals interactions, in combination with atomic force microscopy experiments, to explore the interaction mechanism for three structurally related olympicene molecules adsorbed on the Cu(111) surface. The substitution of a single atom in the olympicene molecule switches the nature of adsorption from predominantly physisorptive character [olympicene on Cu(111)], to an intermediate state [olympicene-derived ketone on Cu(111)], then to chemisorptive character [olympicene radical on Cu(111)]. Despite the remarkable difference in adsorption structures (by up to 0.9 Å in adsorption height) and different nature of bonding, the olympicene, its ketone, and its radical derivatives have essentially identical binding energies and work functions upon interaction with the metal substrate. Our findings suggest that the stability and work functions of molecular adsorbates could be rendered insensitive to their adsorption structures, which could be a useful property for (opto)­electronic applications.