A Single‐Molecule and Logic Gate via Optical and Acid–Base Control

Theoretical Study on the Open-Shell Electronic Structure and Electron Conductivity of [18]Annulene as a Molecular Parallel Circuit Model

Herein, the electron conductivities of [18]annulene and its derivatives are theoretically examined as a molecular parallel circuit model consisting of two linear polyenes. Their electron conductivities are estimated by elastic scattering Green's function (ESGF) theory and density functional theory (DFT) methods. The calculated conductivity of the [18]annulene does not follow the classical conductivity, i.e., Ohm's law, suggesting the importance of a quantum interference effect in single molecules. By introducing electron-withdrawing groups into the annulene framework, on the other hand, a spin-polarized electronic structure appears, and the quantum interference effect is significantly suppressed. In addition, the total current is affected by the spin polarization because of the asymmetry in the coupling constant between the molecule and electrodes. From these results, it is suggested that the electron conductivity as well as the quantum interference effect of π-conjugated molecular systems can be designed using their open-shell nature, which is chemically controlled by the substituents.

Modeling of molecular ternary logic gates and circuits based on diode structures

Modeling in molecular electronics is of great importance, and the use of semiconductor components for this type of modeling accelerates the development process in this field. In this work, a typical circuit model is proposed for modeling molecular components. Accordingly, an asymmetric oligo-phenylene vinylene (OPV) molecular diode and a bipyridine-biborinine molecular diode are modeled. A good agreement is observed between the current curves from the proposed circuit models and the atomic simulations of the molecules. Additionally, the electron density, the distribution of molecular orbitals, and the potential drop profile at + 1 and - 1 V are obtained and analyzed for the bipyridine-biborinine molecular diode using the density functional theory (DFT) in combination with the non-equilibrium Green's function (NEGF). Using different molecular gates and circuits based on the molecular devices, we have modeled the ternary NOT logic gate, ternary NOR logic gate, ternary NAND logic gate, negative ternary inverter (NTI) logic gate, positive ternary inverter (PTI) logic gate, ternary buffer, ternary decoder, and ternary half adder.

Design of multifunctional spin logic gates based on manganese porphyrin molecules connected to graphene electrodes

The spin-resolved transport properties of molecular logic devices composed of two Mn porphyrin molecules connected to each other via a six-carbon atomic chain were studied using the non-equilibrium Green's function combined with density functional theory. The molecules were symmetrically connected to armchair graphene nanoribbon electrodes through four-carbon atomic chains on the left- and right-hand sides. Our calculations revealed that the spin-resolved current-voltage curves depend on the initial spin setting of the transition metal Mn atoms and carbon atoms on the zigzag edges where the electrodes come in contact with the molecule. By simultaneously regulating the spin orientations of the intermediate functional molecules and the zigzag edges of the armchair graphene nanoribbon electrodes, seven spin polarization configurations were obtained. These configurations were examined in this study considering the spin-related symmetry of molecular junctions. By meticulously selecting different combinations according to the specific input and output signals, YES, NOT, OR, NOR, and XOR multifarious spin logic devices were created. The findings of this study are expected to contribute toward the extension of molecular junction functions in future spintronic integrated circuit design and further miniaturization.

Complex molecular logic gates from simple molecules

Herein we describe a protocol to mimic an electronic device. The MLG could function as a transmitter of information at a molecular level and this could be read using the variation of the magnetic field in the molecules.