Electrons Are Transported through Phenylene−Ethynylene Oligomer Monolayers via Localized Molecular Orbitals

Abstract

We report excellent correlations between the first negative threshold potentials (V(TH)s) for electric conduction, electrochemical potentials, and computed lowest unoccupied molecular orbital energies in a series of phenylene-ethynylene oligomers bearing a sulfur-based anchoring unit and different electroactive substituents on the central benzene ring. The theoretical and electrochemical results strongly suggest that the peaks observed in the i-V curves have a true molecular origin and are associated with distinct unoccupied molecular levels of the compounds that are strongly localized on the central ring (except for compound I). This localization might account for the existence of a long-lived radical-anion state that permits lateral electron hopping and leads to charge trapping and storage.

Molecular Electronic Junctions

“…140 Although there is not yet a consensus on the mechanism of NDR observed with STM experiments, the correlation of LUMO energies, reduction potentials, and NDR peak voltages provides strong evidence for a mechanism involving resonant tunneling through the molecule's LUMO. 124,133,135,139,140 A recent report of rectifying molecular junctions by Ashwell et al 141 is based on STM junctions of the type Au(substrate)-S-C 10 H 21 /D-π∠A-C 10 H 20 -S-Au(tip), where D-π-A represents a donor-acceptor molecule with a conjugated bridge. Rectification ratios of 5-18 (at 1 V) were observed, depending on the lengths of the alkane chains.…”

“…The common thread that is emerging from experiments in different laboratories is the relationship among reduction potential, LUMO energy, and rapid electron transfer in a tunnel junction. 133,135,139,172,173 4.2. SAM-Based Monolayer Junctions.…”

Single molecular switch based on thiol tethered iron(II)clathrochelate on gold

“…Nonlinear charge transport in molecules is essential for the development of molecular electronic devices [2][3][4][5][6][7]. Two types of molecular switching behaviour have been observed thus far-switching due to an applied external voltage between the electrodes and stochastic switching attributed to statistical fluctuations in the film or molecule [2,[8][9][10].…”

“…The electronic properties of single molecules or small groups of molecules have been studied by constructing different electrical test beds including electrical and mechanical break junctions [5,8], crosswire junctions [2], conducting-probe atomic force microscopy [28] and scanning tunneling microscopy (STM) [2][3][4][5][6][7][8]28]. STM is a powerful surface analysis technique, as it enables the observation of individual molecules with atomic resolution on surfaces.…”

Electron rectification through donor-acceptor-heterocyclics connected to cumulenic bridge: a computational study

“…The field of molecular electronics is gaining importance in recent times experimentally as well as theoretically [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The era of molecular electronics began with the pioneering theoretical prediction of single D-σ-A molecular rectifier by Aviram and Ratner [19], which mimics the junction diode in nature.…”