Exploring a Linear Combination Feature for Predicting the Conductance of Parallel Molecular Circuits

Abstract

An accurate rule for predicting conductance is the cornerstone of developing molecular circuits and provides a promising solution for miniaturizing electric circuits. The successful prediction of series molecular circuits has proven the possibility of establishing a rule for molecular circuits under quantum mechanics. However, the quantitatively accurate prediction has not been validated by experiments for parallel molecular circuits. Here we used 1,3-dihydrobenzothiophene (DBT) to build the parallel molecular circuits. The theoretical simulation and single-molecule conductance measurements demonstrated that the conductance of the molecule containing one DBT is the unprecedented linear combination of the conductance of the two individual channels with respective contribution weights of 0.37 and 0.63. With these weights, the conductance of the molecule containing two DBTs is predicted as 1.81 nS, matching perfectly with the measured conductance (1.82 nS). This feature offers a potential rule for quantitatively predicting the conductance of parallel molecular circuits.

Effectively Enhancing the Conductance of Asymmetric Molecular Wires by Aligning the Energy Level and Symmetrizing the Coupling

“…The statistical junction lengths of molecules 1 – 3 are 0.81 1.12, and 1.08 nm, respectively. By calibration of the junction length with the “snap-back” length of 0.5 nm, , the measured junction lengths of molecules 1 – 3 are 1.31, 1.62, and 1.58 nm, respectively, which coincide well with the simulated S–S distances (Figure S5 of the Supporting Information). Because the single-molecule conductance often decreases exponentially with the increase of the junction length, the shortest junction length and the lowest conductance in the symmetric molecule 1 imply that the electronic structures should be the key factors in determining the conductance.…”

Hydroxyl Group as the ‘Bridge’ to Enhance the Single-Molecule Conductance by Hyperconjugation

“…The strong throughspace transmission reveals that the connection of the two conjugated fragments in LUMO opens an extra transmission channel for the electron, enhancing the conductance. The transmission coefficients (T(E)) and the transmission pathway for the electron, which investigated the relationship between the electronic structure and the conductance, were calculated by combining density functional theory (DFT) with non-equilibrium Green's functions (NEGF), where the Green's function estimates the behavior of the electron wave in a single molecule and yields the T(E) [12,[33][34][35]. The molecular junctions of 1-5 were simulated while the junction of molecule 6 was reported in previous work [29].…”

“…The single-molecule conductance was measured by scanning tunneling microscopy break junction (STM-BJ) technique using commercially available STM-BJ equipment provided by VR (Xiamen) Technology Co., Ltd. (Xiamen, China) in the 1,2,4-Trichlorobenzene (TCB) solution containing 0.1 mM of synthesized molecule [ 40 ]. The bias voltage applied between electrodes was 100 mV [ 33 , 41 ]. The retraction rate of electrodes was calibrated using the reported method in pure TCB solvent as a blank experiment ( Figure S13 ) [ 42 ].…”