Solvent molecules in an epitaxially grown scaffold of star-shaped nanographenes

A scanning tunneling microscopy (STM) study of a star-shaped hexa-peri-hexabenzocoronene (HBC-star) derivative at solid-solution interfaces is presented. The star-shape of the molecules provides voids at their periphery which can be filled by smaller molecules. The use of solvents with different affinities to fill the voids allows for the fine-tuning of the structure of self-assembled architectures of HBC-stars. This concept is demonstrated by the use of solvents of different polarity and size, which leads to the formation of complex, epitaxial architectures at the interface. For small polar solvent molecules, a surprising decrease of the tunneling barrier is observed. The self-assembled architecture may serve as a useful model system for studying the dependence of electron tunneling on order, mobility, and polarity of adsorbates.