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]thiophene diphenyl (DTT) molecules deposited onto Au(111) electrode from a dosing solution made of dichlorobenzene and 50 muM DTT. Potential control was proven to be of prime importance in guiding the arrangement of DTT admolecules on Au(111) in 0.1 M HClO(4), as disorder DTT adlayer seen at E > 0.3 V (vs reversible hydrogen electrode) was transformed into a highly ordered (2 x 7 square 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 square 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 square root(3))rect-2DTT structure and registries of admolecules were deduced. The dynamics of the DTT 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.