The phase transition of 2,5-distyrylpyrazine (DSP) adsorbed on Au(111) substrate was studied as a function of the substrate potential in 0.1 M HClO 4 , using an in situ scanning tunneling microscope (STM). Depending on the applied electric field, DSP formed three distinctly different, two-dimensionally (2D) ordered, supramolecular nanostructures on the Au(111) surface. In the potential range of 0.55 V < E < 0.75 V, the DSP molecules formed a close-packed stripe pattern with the adlayer structure 1 3 . 8 6 When the potential was reduced to 0.45 V < E < 0.55 V, a ridge-like pattern built from dimer subunits was observed, with the adlayer structure 4 5 . 12 4 Further decreasing in the electrode potential to 0.2 V < E < 0.45 V caused the appearance of a herringbone-like pattern consisting of dimer subunits, with the adlayer structure 9 0 . 3 9 The potential-induced phase transitions revealed the structure-determining role of substrate-adsorbate coordination and intermolecular interaction in forming the distinct 2D adlayer motifs.
