In Situ STM Imaging of Fused Thienothiopene Molecules Adsorbed on Au(111) Electrode

In situ scanning tunneling microscopy (STM) was used to reveal the structures of dithieno[2,3-b:3,2-d]hiophene diphenyl (DTT) molecules deposited onto Au(111) electrode from a dosing solution made of dichlorobenzene and 50 mu M DTT. Potential control was proven to be of prime importance in guiding the arrangement of DTT admolecules on Au(111) in 0.1 M HClO4, as disorder DTT adlayer seen at E > 0.3 V (vs reversible hydrogen electrode) was transformed into a highly ordered (2 x 7 root 3)rect -2DTT structure when the potential was made to 0.05 to 0.2 V. The ordered structure was stable for hours between 0.05 and 0.2 V. However, switching the potential further negative to 0 V resulted in slow melting of the ordered structure. The (2 x 7 root 3)rect-DTT ordered adlattices recuperated when the potential was made positive to 0.2 V. Internal molecular functionalities of the thienothiophene and benzene in DTT admolecules were clearly discerned, from which the lateral structure for the (2 x 7 root 3)rect-2DTT structure and registries of admolecules were deduced. The dynamics of the Dry adlattices on the Au(111) electrode surface was examined by real-time STM imaging, showing reorientation of as many as 150 DTT admolecules to join a neighboring ordered array within minutes.