Molecular rectification: self-assembled monolayers of a donor–(π-bridge)–acceptor chromophore connected via a truncated Au–S–(CH2)3 bridge

Abstract

Bis-[1-{(3-propyl)-4-(2-(4-dimethylaminophenyl)vinyl)quinolinium}]disulfide diodide interacts with gold to form self-assembled monolayers, the thickness and contact area being 2.25 ± 0.05 nm and 0.30 ± 0.03 nm² molecule⁻¹ respectively. The films exhibit asymmetric current–voltage characteristics with a rectification ratio of ca. 12 at ±1 V. These become symmetrical when the intramolecular charge-transfer axis is suppressed by protonation but the electrical asymmetry is restored when the films are exposed to base. Molecular rectification is intrinsic to the bridged donor–acceptor combination.