Thermal Transport through Single-Molecule Junctions

Molecular junctions exhibit a rich and tunable set of thermal transport phenomena. However, the predicted high thermoelectric efficiencies, phonon quantum interference effects, rectification, and nonlinear heat transport properties of organic molecules are yet to be verified because suitable experimental techniques have been missing. Here, by combining the break junction technique with suspended heat-flux sensors with picowatt per Kelvin sensitivity, we measured the thermal and electrical conductance of single organic molecules at room temperature simultaneously. We used this method to study the thermal transport properties of two model systems, namely, dithiol-oligo­(phenylene ethynylene) and octane dithiol junctions with gold electrodes. In agreement with our density functional theory and phase-coherent transport calculations, we show that heat transport across these systems is governed by the phonon mismatch between the molecules and the metallic electrodes. This work represents the first measurement of thermal transport through single molecules and opens new opportunities for studying heat management at the nanoscale level

Thermal Transport through Single-Molecule Junctions

Molecular junctions exhibit a rich and tunable set of thermal transport phenomena. However, the predicted high thermoelectric efficiencies, phonon quantum interference effects, rectification, and nonlinear heat transport properties of organic molecules are yet to be verified because suitable experimental techniques have been missing. Here, by combining the break junction technique with suspended heat-flux sensors with picowatt per Kelvin sensitivity, we measured the thermal and electrical conductance of single organic molecules at room temperature simultaneously. We used this method to study the thermal transport properties of two model systems, namely, dithiol-oligo­(phenylene ethynylene) and octane dithiol junctions with gold electrodes. In agreement with our density functional theory and phase-coherent transport calculations, we show that heat transport across these systems is governed by the phonon mismatch between the molecules and the metallic electrodes. This work represents the first measurement of thermal transport through single molecules and opens new opportunities for studying heat management at the nanoscale level

Thermal Transport through Single-Molecule Junctions

Molecular junctions exhibit a rich and tunable set of thermal transport phenomena. However, the predicted high thermoelectric efficiencies, phonon quantum interference effects, rectification, and nonlinear heat transport properties of organic molecules are yet to be verified because suitable experimental techniques have been missing. Here, by combining the break junction technique with suspended heat-flux sensors with picowatt per Kelvin sensitivity, we measured the thermal and electrical conductance of single organic molecules at room temperature simultaneously. We used this method to study the thermal transport properties of two model systems, namely, dithiol-oligo­(phenylene ethynylene) and octane dithiol junctions with gold electrodes. In agreement with our density functional theory and phase-coherent transport calculations, we show that heat transport across these systems is governed by the phonon mismatch between the molecules and the metallic electrodes. This work represents the first measurement of thermal transport through single molecules and opens new opportunities for studying heat management at the nanoscale level

Phase Tag-Assisted Synthesis of Benzo[<i>b</i>]carbazole End-Capped Oligothiophenes

The introduction and removal of a phase tag have been used to trigger cyclization events in a new synthesis of benzo[<i>b</i>]carbazoles. The approach has been exploited in a tag-assisted approach to new benzo[<i>b</i>]carbazole end-capped oligothiophenes for preliminary evaluation as semiconductors

A Sm(II)-Mediated Cascade Approach to Dibenzoindolo[3,2‑<i>b</i>]carbazoles: Synthesis and Evaluation

Previously unstudied dibenzoindolo­[3,2-<i>b</i>]­carbazoles have been prepared by two-directional, phase tag-assisted synthesis utilizing a connective-Pummerer cyclization and a SmI₂-mediated tag cleavage–cyclization cascade. The use of a phase tag allows us to exploit unstable intermediates that would otherwise need to be avoided. The novel materials were characterized by X-ray, cyclic voltammetry, UV–vis spectroscopy, TGA, and DSC. Preliminary studies on the performance of OFET devices are also described

A Sm(II)-Mediated Cascade Approach to Dibenzoindolo[3,2‑<i>b</i>]carbazoles: Synthesis and Evaluation

Previously unstudied dibenzoindolo­[3,2-<i>b</i>]­carbazoles have been prepared by two-directional, phase tag-assisted synthesis utilizing a connective-Pummerer cyclization and a SmI₂-mediated tag cleavage–cyclization cascade. The use of a phase tag allows us to exploit unstable intermediates that would otherwise need to be avoided. The novel materials were characterized by X-ray, cyclic voltammetry, UV–vis spectroscopy, TGA, and DSC. Preliminary studies on the performance of OFET devices are also described

Extended conjugation in poly(triarylamine)s: synthesis, structure and impact on field-effect mobility

No description supplie

Single-Molecule Conductance of Functionalized Oligoynes: Length Dependence and Junction Evolution

We report a combined experimental and theoretical investigation of the length dependence and anchor group dependence of the electrical conductance of a series of oligoyne molecular wires in single-molecule junctions with gold contacts. Experimentally, we focus on the synthesis and properties of diaryloligoynes with <i>n</i> = 1, 2, and 4 triple bonds and the anchor dihydrobenzo­[<i>b</i>]­thiophene (BT). For comparison, we also explored the aurophilic anchor group cyano (CN), amino (NH₂), thiol (SH), and 4-pyridyl (PY). Scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques are employed to investigate single-molecule conductance characteristics. The BT moiety is superior as compared to traditional anchoring groups investigated so far. BT-terminated oligoynes display a 100% probability of junction formation and possess conductance values which are the highest of the oligoynes studied and, moreover, are higher than other conjugated molecular wires of similar length. Density functional theory (DFT)-based calculations are reported for oligoynes with <i>n</i> = 1–4 triple bonds. Complete conductance traces and conductance distributions are computed for each family of molecules. The sliding of the anchor groups leads to oscillations in both the electrical conductance and the binding energies of the studied molecular wires. In agreement with experimental results, BT-terminated oligoynes are predicted to have a high electrical conductance. The experimental attenuation constants β_H range between 1.7 nm^–1 (CN) and 3.2 nm^–1 (SH) and show the following trend: β_H(CN) < β_H(NH₂) < β_H(BT) < β_H(PY) ≈ β_H(SH). DFT-based calculations yield lower values, which range between 0.4 nm^–1 (CN) and 2.2 nm^–1 (PY)

Single-Molecule Conductance of Functionalized Oligoynes: Length Dependence and Junction Evolution

We report a combined experimental and theoretical investigation of the length dependence and anchor group dependence of the electrical conductance of a series of oligoyne molecular wires in single-molecule junctions with gold contacts. Experimentally, we focus on the synthesis and properties of diaryloligoynes with <i>n</i> = 1, 2, and 4 triple bonds and the anchor dihydrobenzo­[<i>b</i>]­thiophene (BT). For comparison, we also explored the aurophilic anchor group cyano (CN), amino (NH₂), thiol (SH), and 4-pyridyl (PY). Scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques are employed to investigate single-molecule conductance characteristics. The BT moiety is superior as compared to traditional anchoring groups investigated so far. BT-terminated oligoynes display a 100% probability of junction formation and possess conductance values which are the highest of the oligoynes studied and, moreover, are higher than other conjugated molecular wires of similar length. Density functional theory (DFT)-based calculations are reported for oligoynes with <i>n</i> = 1–4 triple bonds. Complete conductance traces and conductance distributions are computed for each family of molecules. The sliding of the anchor groups leads to oscillations in both the electrical conductance and the binding energies of the studied molecular wires. In agreement with experimental results, BT-terminated oligoynes are predicted to have a high electrical conductance. The experimental attenuation constants β_H range between 1.7 nm^–1 (CN) and 3.2 nm^–1 (SH) and show the following trend: β_H(CN) < β_H(NH₂) < β_H(BT) < β_H(PY) ≈ β_H(SH). DFT-based calculations yield lower values, which range between 0.4 nm^–1 (CN) and 2.2 nm^–1 (PY)

Single-Molecule Conductance of Functionalized Oligoynes: Length Dependence and Junction Evolution

We report a combined experimental and theoretical investigation of the length dependence and anchor group dependence of the electrical conductance of a series of oligoyne molecular wires in single-molecule junctions with gold contacts. Experimentally, we focus on the synthesis and properties of diaryloligoynes with <i>n</i> = 1, 2, and 4 triple bonds and the anchor dihydrobenzo­[<i>b</i>]­thiophene (BT). For comparison, we also explored the aurophilic anchor group cyano (CN), amino (NH₂), thiol (SH), and 4-pyridyl (PY). Scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques are employed to investigate single-molecule conductance characteristics. The BT moiety is superior as compared to traditional anchoring groups investigated so far. BT-terminated oligoynes display a 100% probability of junction formation and possess conductance values which are the highest of the oligoynes studied and, moreover, are higher than other conjugated molecular wires of similar length. Density functional theory (DFT)-based calculations are reported for oligoynes with <i>n</i> = 1–4 triple bonds. Complete conductance traces and conductance distributions are computed for each family of molecules. The sliding of the anchor groups leads to oscillations in both the electrical conductance and the binding energies of the studied molecular wires. In agreement with experimental results, BT-terminated oligoynes are predicted to have a high electrical conductance. The experimental attenuation constants β_H range between 1.7 nm^–1 (CN) and 3.2 nm^–1 (SH) and show the following trend: β_H(CN) < β_H(NH₂) < β_H(BT) < β_H(PY) ≈ β_H(SH). DFT-based calculations yield lower values, which range between 0.4 nm^–1 (CN) and 2.2 nm^–1 (PY)