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Electrically conductive molecular junctions are highly desirable components for applications in future molecular-scale electronic circuits. Here, we demonstrate an electrically conductive hybrid mo...

Electric switches are one of the most fundamental electric circuitries. Recent developments in single-molecule techniques allow us to study various electric-switching phenomena on the single-molecule scale. In this study, the switch of the current through a single molecule of a biphenothiazine derivative was investigated using the break junction technique. The biphenothiazine derivative undergoes acid-base reaction-induced electronic modulation due to the reversible structural transformation between a closed shell and an open shell, resulting in a change in the electronic gap and effective tunneling barrier height. We succeeded in controlling the single-molecule electric conductivity of the biphenothiazine derivative wired to two Au electrodes by allowing the reaction to proceed reversibly on the electrode.

An analysis combining SERS and current–voltage response measurements with DFT calculations has identified the molecular adsorption site in a single molecule junction., Single-molecule junctions are ideal test beds for investigating the fundamentals of charge transport at the nanoscale. Conducting properties are strongly dependent on the metal–molecule interface geometry, which, however, is very poorly characterized due to numerous experimental challenges. We report on a new methodology for characterizing the adsorption site of single-molecule junctions through the combination of surface enhanced Raman scattering (SERS), current–voltage (I–V) curve measurements, and density functional theory simulations. This new methodology discriminates between three different adsorption sites for benzenedithiol and aminobenzenethiol junctions, which cannot be identified by solo measurements of either SERS or I–V curves. Using this methodology, we determine the interface geometry of these two prototypical molecules at the junction and its time evolution. By modulating the applied voltage, we can change and monitor the distribution of adsorption sites at the junction.

We have investigated the effect of the bias voltage on the 1,4-benzenethiol (BDT) single-molecule junction using the surface-enhanced Raman scattering (SERS). By measuring the bias voltage dependen...

A triphosphasumanene trisulfide was designed and synthesized as an out-of-plane anisotropic π-conjugated molecule. Incorporating three anisotropic phosphine sulfide moieties into a sumanene skeleton induced a cumulative anisotropy with a large dipole moment (12.0 D), which is aligned in perpendicular direction with respect to the π-framework and more than twice as large as those of conventional out-of-plane anisotropic molecules. In the crystal, the molecules align to form columnar structures, in which electron-rich and electron-deficient sides of the π-framework face each other. The interactions between the electron-rich surfaces, which contain three sulfur atoms, and Au(111) were examined by X-ray photoelectron spectroscopy.

The electronic and magnetic properties of chemically modified graphene armchair edges are studied using a combination of tight-binding calculations, first-principles modelling, and low temperature scanning tunneling microscopy (STM) experiments. The atomically resolved STM images of the hydrogen etched graphitic edges suggest the presence of localized states at the Fermi level for certain armchair edges. We demonstrate theoretically that the topological zero-energy edge mode may emerge at armchair boundaries with asymmetrical chemical termination of the two outermost atoms in the unit cell. We particularly focus our attention on armchair edges terminated by various combinations of the hydrogen (H, H2) and methylene (CH2) groups. The inclusion of the spin component in our calculations reveals the appearance of π-electron-based magnetism at the armchair edges under consideration.

To gain a fundamental understanding of atomic- and molecular-scale electronic transport phenomena, as well as the practical application of a single-molecule junction for molecular electronics, it is necessary to establish a reliable electronic and structural characterization method for single-molecule junctions. Recent advances in characterization methods make it possible to elucidate the unique electronic functionality of a quasi-one-dimensional conductor for a single-molecule junction. This review presents some of the current methods used to address the electronic and structural details of a single-molecule junction. We discuss the potential applications of single-molecule junctions as molecular switches, diodes, and transistors in single-molecule electronic devices.

Fabrication of oxygen molecular junctions was demonstrated for a series of single metal wires of Au, Ag, and Cu using the mechanically controllable break junction method at low temperature (10 K). On the basis of conductance measurement, vibrational spectroscopy, and current–voltage (I–V) response of the molecular junctions, we provide experimental evidence that the oxygen can incorporate into the metal wires to form single oxygen molecular junctions. Conductance behavior during the elongation process of the molecular junctions revealed the formation of single one-dimensional wire. The incorporation of oxygen into the metal wires was demonstrated in vibrational spectroscopy and I–V response measurements. Furthermore, detailed analysis of the I–V response based on the single channel transport model allowed us to quantitatively evaluate electronic properties of the molecular junctions as metal–molecule electronic couplings and an energy level of a transport channel. The present study demonstrated that oxyge...

[Image: see text] When employing self-assembled monolayers (SAMs) for tuning surface and interface properties, organic molecules that enable strong binding to the substrate, large-area structural uniformity, precise alignment of functional groups, and control of their density are highly desirable. To achieve these goals, tripod systems bearing multiple bonding sites have been developed as an alternative to conventional monodentate systems. Bonding of all three sites has, however, hardly been achieved, with the consequence that structural uniformity and orientational order in tripodal SAMs are usually quite poor. To overcome that problem, we designed 1,8,13-trimercaptomethyltriptycene (T1) and 1,8,13-trimercaptotriptycene (T2) as potential tripodal SAM precursors and investigated their adsorption behavior on Au(111) combining several advanced experimental techniques and state-of-the-art theoretical simulations. Both SAMs adopt dense, nested hexagonal structures but differ in their adsorption configurations and structural uniformity. While the T2-based SAM exhibits a low degree of order and noticeable deviation from the desired tripodal anchoring, all three anchoring groups of T1 are equally bonded to the surface as thiolates, resulting in an almost upright orientation of the benzene rings and large-area structural uniformity. These superior properties are attributed to the effect of conformationally flexible methylene linkers at the anchoring groups, absent in the case of T2. Both SAMs display interesting electronic properties, and, bearing in mind that the triptycene framework can be functionalized by tail groups in various positions and with high degree of alignment, especially T1 appears as an ideal docking platform for complex and highly functional molecular films.

Single-molecule junctions, in which a single molecule bridges a gap between metal electrodes, have attracted significant attention due to their potential applications in ultra-small electronic devices and their unique structure. Single-molecule junctions are one-dimensional nanomaterials having two metal–molecule interfaces. Thus, unconventional properties and functionalities that would not be observed in other phases (e.g., isolated molecules and bulk crystals) are expected to appear in these nanomaterials. Despite interest in these expected unconventional properties, several issues have been noted with the investigation and practical application of the unique properties of single-molecule junctions. To explore new functionality, we have investigated single-molecule junctions using a combined approach comprising fabrication, characterization, and measurement. First, we have explored a new generation of the metal–molecule interfaces formed by direct π-bonding. The interfaces made by the direct π-bonding h...

The concise synthesis of C3-symmetrical [12]CPP-hexacarboxylate has been achieved through macrocyclization by the rhodium-catalyzed intermolecular cross-cyclotrimerization and subsequent reductive aromatization. C3-Symmetrical functionalization of CPP with highly polar alkoxycarbonyl groups enabled the structurally uniform nanotube assembly in the crystalline state through multiple hydrogen-bonding interactions giving a dimer followed by one-dimensional stacking.