Electron transport through dipyrimidinyl-diphenyl diblock molecular wire: protonation effect

TL;DR

This study investigates how protonation influences electron transport in a specific molecular wire, revealing conductance enhancement and rectification, but not reversing current direction, with implications for molecular electronics design.

Contribution

The paper provides first-principles calculations showing protonation affects conductance and rectification in dipyrimidinyl-diphenyl molecular wires, clarifying experimental observations.

Findings

Protonation enhances conductance and rectification.

Rectification direction remains consistent regardless of protonation.

Molecule-electrode anchoring geometry does not explain experimental discrepancies.

Abstract

Recently, rectifying direction inversion has been observed in dipyrimidinyl-diphenyl (PMPH) diblock molecular wire [J. Am. Chem. Soc. (2005) 127, 10456], and a protonation mechanism was suggested to explain this interesting phenomena. In this paper, we study the protonation effect on transport properties of PMPH molecule by first principles calculations. No significant rectification is found for the pristine diblock molecular wire. Protonation leads to conductance enhancement and rectification. However, for all considered junctions with rectifying effect, the preferential current directions are samely from dipyrimidinyl side to diphenyl side. Effect of molecule-electrode anchoring geometry is studied, and it is not responsible for the discrepancy between experiment and theory.