The First Studies of a Tetrathiafulvalene‐σ‐Acceptor Molecular Rectifier

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Abstract
Langmuir–Blodgett monolayers of a donor–acceptor diad TTF‐σ‐(trinitrofluorene) (8) with an extremely low HOMO–LUMO gap (0.3 eV) have been used to create molecular junction devices that show rectification behavior. By virtue of structural similarities and position of molecular orbitals, 8 is the closest well‐studied analogue of the model Aviram–Ratner unimolecular rectifier (TTF‐σ‐TCNQ). Compressing the monolayer results in aligning the molecules, and is followed by a drastic increase in the rectification ratio. The direction of rectification depends on the electrodes used and is different in n‐Si/8/Ti and Au/8/C16H33S‐Hg junctions. The molecular nature of such behavior was corroborated by control experiments with fatty acids and by reversing the rectification direction with changing the molecular orientation (Au/D‐σ‐A versus Au/A‐σ‐D).