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The single‐molecule electronic devices offer the ultimate solution to miniaturize integrated circuits, and subthreshold swing (SS) is the key indicator of the power consumption for single‐molecule transistors but is still quite restricted. In this study, the redox‐mediated single‐molecule transistor with a SS down to 120 mV decade−1 in the faradaic potential region via the electrochemical‐STM break junction (EC‐STM‐BJ) technique is fabricated. With an off‐state leakage current of less than 10 pA and an on/off ratio of 100, the balance between low static power consumption and a high switching ratio is achieved. The theoretical investigations reveal that the conductance tuning is from the difference of transmission in the redox process. The study provides a new strategy for the design of single‐molecule transistors with promising SS, which is essential for the potential application of single‐molecule devices. [ABSTRACT FROM AUTHOR]

The single‐molecule electronic devices offer the ultimate solution to miniaturize integrated circuits, and subthreshold swing (SS) is the key indicator of the power consumption for single‐molecule transistors but is still quite restricted. In this study, the redox‐mediated single‐molecule transistor with a SS down to 120 mV decade−1 in the faradaic potential region via the electrochemical‐STM break junction (EC‐STM‐BJ) technique is fabricated. With an off‐state leakage current of less than 10 pA and an on/off ratio of 100, the balance between low static power consumption and a high switching ratio is achieved. The theoretical investigations reveal that the conductance tuning is from the difference of transmission in the redox process. The study provides a new strategy for the design of single‐molecule transistors with promising SS, which is essential for the potential application of single‐molecule devices. [ABSTRACT FROM AUTHOR]

C-H···π interactions, a prevalent intermolecular force, play a pivotal role in chemistry, materials science, and life sciences. Despite extensive studies of their influence on intermolecular binding configurations and energetics, their impact on intermolecular coupling and charge transport remains unexplored. Here, we investigate the charge transport within supramolecular junctions connected by C-H···π and π-π interactions, respectively, and find that C-H···π interactions exhibit conductances that are 3.5 times those of π-π interactions. Angstrom-scale distance-dependent experiments indicate that the conductance of C-H···π supramolecular junctions experiences initial decay under stretching, followed by gradual convergence, in contrast with the periodic fluctuations in π-π stacked supramolecular junctions. Theoretical calculations show that charge transport within C-H···π interactions transitions from destructive to constructive quantum interference under stretching, with a larger range of constructive quantum interference compared with π-π stacking. This study establishes that C-H···π interactions facilitate efficient intermolecular charge transport and elucidates the evolution of quantum interference effects with assembly configuration, offering critical insights for the design of supramolecular materials and devices.

Nucleophilic substitution is one of the most fundamental chemical reactions, and the pursuit of high reaction rates of the reaction is one of the ultimate goals in catalytic and organic chemistry. The reaction barrier of the nucleophilic substitution originates from the highly polar nature of the transition state that can be stabilized under the electric field created by the solvent environment. However, the intensity of the induced solvent-electric field is relatively small due to the random orientation of solvent molecules, which hinders the catalytic effects and restricts the reaction rates. This work shows that oriented external electric fields applied within a confined nanogap between two nanoscopic tips could accelerate the Menshutkin reaction by more than four orders of magnitude (over 39 000 times). The theoretical calculations reveal that the electric field inside the nanogap reduces the energy barrier to increase the reaction rate. Our work suggests the great potential of electrostatic catalysis for green synthesis in the future., Competing Interests: There is no conflict of interest to report., (This journal is © The Royal Society of Chemistry.)

Pyridinium has been shown to be a cocatalyst for the electrochemical reduction of CO 2 on metal and semiconductor electrodes, but its exact role has been difficult to elucidate. In this work, we create cooperative cobalt-protoporphyrin (CoPP) and pyridine/pyridinium (py/pyH + ) catalytic sites on metal-organic layers (MOLs) for an electrocatalytic CO 2 reduction reaction (CO 2 RR). Constructed from [Hf 6 (μ 3 -O) 4 (μ 3 -OH) 4 (HCO 2 ) 6 ] secondary building units (SBUs) and terpyridine-based tricarboxylate ligands, the MOL was postsynthetically functionalized with CoPP via carboxylate exchange with formate capping groups. The CoPP group and the pyridinium (pyH + ) moiety on the MOL coactivate CO 2 by forming the [pyH + - - O 2 C-CoPP] adduct, which enhances the CO 2 RR and suppresses hydrogen evolution to afford a high CO/H 2 selectivity of 11.8. Cooperative stabilization of the [pyH + - - O 2 C-CoPP] intermediate led to a catalytic current density of 1314 mA/mgCo for CO production at -0.86 V RHE , which corresponds to a turnover frequency of 0.4 s -1 .

We report an order-disorder phase transition in the 2D semiconductor KAg 3 Se 2 , which is a dimensionally reduced derivative of 3D Ag 2 Se. At ∼695 K, the room temperature β-phase (CsAg 3 S 2 structure type, monoclinic space group C2/ m) transforms to the high temperature α-phase (new structure type, hexagonal space group R3̅ m, a = 4.5638(5) Å, c = 25.4109(6) Å), as revealed by in situ temperature-dependent X-ray diffraction. Significant Ag + ion disorder accompanies the phase transition, which resembles the low temperature (∼400 K) superionic transition in the 3D parent compound. Ultralow thermal conductivity of ∼0.4 W m -1 K -1 was measured in the "ordered" β-phase, suggesting anharmonic Ag motion efficiently impedes phonon transport even without extensive disordering. The optical and electronic properties of β-KAg 3 Se 2 are modified as expected in the context of the dimensional reduction framework. UV-vis spectroscopy shows an optical band gap of ∼1 eV that is indirect in nature as confirmed by electronic structure calculations. Electronic transport measurements on β-KAg 3 Se 2 yielded n-type behavior with a high electron mobility of ∼400 cm 2 V -1 s -1 at 300 K due to a highly disperse conduction band. Our results thus imply that dimensional reduction may be used as a design strategy to frustrate order-disorder phenomena while retaining desirable electronic and thermal properties.

Metal-organic layers (MOLs) represent an emerging class of tunable and functionalizable two-dimensional materials. In this work, the scalable solvothermal synthesis of self-supporting MOLs composed of [Hf6O4(OH)4(HCO2)6] secondary building units (SBUs) and benzene-1,3,5-tribenzoate (BTB) bridging ligands is reported. The MOL structures were directly imaged by TEM and AFM, and doped with 4'-(4-benzoate)-(2,2',2''-terpyridine)-5,5''-dicarboxylate (TPY) before being coordinated with iron centers to afford highly active and reusable single-site solid catalysts for the hydrosilylation of terminal olefins. MOL-based heterogeneous catalysts are free from the diffusional constraints placed on all known porous solid catalysts, including metal-organic frameworks. This work uncovers an entirely new strategy for designing single-site solid catalysts and opens the door to a new class of two-dimensional coordination materials with molecular functionalities., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)