Redox-addressable single-molecule junctions incorporating a persistent organic radical

The integration of radical (open-shell) species into single-molecule junctions at non-cryogenic temperatures is a key to unlocking the potential of molecular electronics in further applications. While many efforts have been devoted to this issue, in the absence of a chemical or electrochemical potential the open-shell character is lost when in contact with the metallic electrodes. Here, the organic 6-oxo-verdazyl radical, which is stable at ambient temperatures and atmosphere, has been functionalised by aurophilic 4-thioanisole groups at the 1,5-positions and fabricated into a molecular junction using the scanning tunnelling microscope break-junction technique. The verdazyl moiety retains open-shell character within the junction even at room temperature, and electrochemical gating permits in-situ reduction of the verdazyl to the closed-shell anionic state in a single-molecule transistor configuration. In addition, the bias-dependent alignment of the open-shell resonances with respect to the electrode Fermi levels gives rise to purely electronically-driven rectifying behaviour. The demonstration of a verdazyl-based molecular junction capable of integrating radical character, transistor-like switching behaviour, and rectification in a single molecular component under ambient conditions paves the way for further studies of the electronic, magnetic, and thermoelectric properties of open-shell species.

Theoretical Design of thermal spin molecular logic gates by using a combinational molecular junction

Based on the density functional theory combined with the non-equilibrium Green’s function methodology, we have studied the thermally-driven spin-dependent transport properties of a combinational molecular junction consisting of a planar four-coordinate Fe molecule and a 15,16-dinitrile dihydropyrene/cyclophanediene molecule with single-walled carbon nanotube bridge and electrode. Our results show that the magnetic field and light can effectively regulate the thermally-driven spin-dependent currents. Perfect thermal spin-filtering effect and good thermal switching effect are realized. The results are explained by the Fermi-Dirac distribution function, the spin-resolved transmission spectra, the spatial distribution of molecular projected self-consistent Hamiltonian orbitals, and the spin-resolved current spectra. On the basis of these thermally-driven spin-dependent transport properties, we further design three basic thermal spin molecular AND, OR and NOT gates.

Comparative Study of Symmetrical And Asymmetrical B40 Molecular Junctions

The quantum transport in symmetric and asymmetric borospherne based molecular junction with adenine has been probed. Adenine is a nucleobase of DNA among the four nucleobases of DNA, adenine is selected because of its excellent transport properties. The DFT-NEGF mathematical approach has been utilized. This was further used to calculate quantum transport parameters such as the I-V curve, transmission spectra, highest occupied molecular orbital (HOMO)- lowest occupied molecular orbital (LUMO) gap (HLG), differential conductance, and transmission pathways. From our research work we have noticed that both symmetric and asymmetric devices exhibit non-linear behavior thus leading to non-differential resistance (NDR). Alos symmetric B40 molecular device has reduced HLG in contrast to asymmetric B40 molecular device. This drop-in HLG is due to a reduction in electron density. A high rectification ratio for the devices is observed at 0.2V. Hence symmetric and asymmetric B40 molecular junction is the potential candidates that can be utilized in future nano-scale devices.