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 HC104, 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 （81 ）. When theptentiawareducedt45V〈E〈.55Varidge-ikepaernbuitfrmdimersubunitswasb- 4 5）. decreasing in the electrode potential to 0.2 V 〈 E 〈 0.45 V caused the served, with the adlayer structure -12 Further fn appearance of a herringbone-like pattern consisting of dimer subunits, with the adlayer structure The potential-induced phase transitions revealed the structure-determining role of substrate-adsorbate coordination and intermolecular interaction in forming the distinct 2D adlayer motifs.
