STM Study of Dithia[7]Helicenes and the Role of an Organic Solvent at Ambient Conditions

Using a Scanning Tunneling Microscope (STM), we study a solution of the chiral molecule dithia[7]helicene ([7]DTH) in benzene. Two different [7]DTH were synthesized with sulfur atoms integrated in different locations displaying two different topologies. After the deposition and evaporation on Au(111), we studied the molecular arrangement over the surface, showing differences due to the interaction of the sulfur atom as a link group with the gold atoms. In our study we could image the different binding configurations of the molecules and characterize their main characteristics including their chirality.

When working with diluted solutions, it was possible to distinguish the solvents from the target molecules. Thus, in the curse of the study of the helicenes, we studied three common organic solvents: benzene, cyclohexane and toluene. Our results show thin adsorbed molecular layers of the solvents after evaporation in gold surface. STM images resolve solvent single molecules over the adsorbed film, meaning a good adhesion of the solvent molecules, allowing us to measure the molecular diameter at room conditions.

Finally, we performed electronic transport measurements on solvents by STM-BJ which show the most probable conductance values due to the formation of different molecular bridges. Therefore, helping us to understand the role of physiosorbed molecules of solvents in molecular transport experiments at ambient conditions.