Controlling Single Molecule Conductance by a Locally Induced Chemical Reaction on Individual Thiophene Units

Abstract

Among the prerequisites for the progress of single‐molecule‐based electronic devices are a better understanding of the electronic properties at the individual molecular level and the development of methods to tune the charge transport through molecular junctions. Scanning tunneling microscopy (STM) is an ideal tool not only for the characterization, but also for the manipulation of single atoms and molecules on surfaces. The conductance through a single molecule can be measured by contacting the molecule with atomic precision and forming a molecular bridge between the metallic STM tip electrode and the metallic surface electrode. The parameters affecting the conductance are mainly related to their electronic structure and to the coupling to the metallic electrodes. Here, the experimental and theoretical analyses are focused on single tetracenothiophene molecules and demonstrate that an in situ‐induced direct desulfurization reaction of the thiophene moiety strongly improves the molecular anchoring by forming covalent bonds between molecular carbon and copper surface atoms. This bond formation leads to an increase of the conductance by about 50 % compared to the initial state.

Potential-Controlled Organization of 2,3-Diphenyl-5,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine Adsorbed on Au(111) and Au(100) Electrodes

“…21,22 A recent study shows the use of STM to modify the chemical structure of polythiophene molecules and to measure the conductivity of an artificial molecule. 23 The current study aimed at providing insights into the adsorption and organization of DPDTTP molecules on Au(111) and Au(100) electrodes as functions of potential control, chemical identity of the supporting electrolyte, and substrate orientation. We also explored the susceptibility to electrochemical oxidation and reduction of thiophene and pyrazine-based DPDTTP molecules at the Au electrode.…”

“…It is realized that practical applications of these organic materials can benefit from a fundamental understanding of the molecular adsorption configuration and organization in an extended organic thin film supported by a metallic substrate such as Au. , Over the past decade, scanning tunneling microscopy (STM) has been used to study the organization of thiophene-based organic molecules on a number of substrates, including Au, − Cu, HOPG, , and Si . STM is considered as an indispensable tool to gain insights into the spatial arrangement and electronic properties of organic thin films at a molecular level. , A recent study shows the use of STM to modify the chemical structure of polythiophene molecules and to measure the conductivity of an artificial molecule …”

Chiral and Catalytic Effects of Site-Specific Molecular Adsorption

“…Furthermore, the adsorption properties associated with induced catalytic activity at metallic surfaces can be responsible for the formation of new molecular structures and materials. − A particular example is the desulfurization reaction, required for the removal of sulfur atoms from crude oils, due to the harmful effects of sulfur compounds in the natural environment. − In previous studies, we have investigated the electric-field-induced desulfurization reaction of tetracenothiophene (TCT) molecules adsorbed on a Cu(111) surface and its effect on the molecular conductance across the molecular derivative product TC-D . Here, we analyze the adsorption characteristics and the effect of the interaction of TCT and TC-D molecules with the surface and subsurface substrate atoms on the surface-induced chirality.…”

“…Intact TCT molecules (see molecular structure in Figure a) are deposited in a submonolayer regime onto the Cu(111) surface, maintaining the substrate temperature below 280 K. The molecules are adsorbed with their long axis along the high-symmetry crystallographic directions of the substrate (Figure a). In the topographic STM images, the molecules have an asymmetric “dumbbell-like” appearance, with the brighter side at the thiophene unit. , The images were acquired at a temperature of about 6 K (Figure b).…”

“…Direct Desulfurization Reaction of Tetracenothiophene . As previously mentioned, the adsorption of TCT on the Cu(111) surface at room temperature activates the cleavage of the S–C bonds from a portion of the adsorbed molecules and results in a desulfurized tetraceno derivative TC-D being strongly bound to the surface. In Figure a, the electronic states of the TCT and TC-D molecules close to the Fermi energy are mapped-out with a functionalized tip.…”