Orbital Views of Molecular Conductance Perturbed by Anchor Units

Abstract

Site-specific electron transport phenomena through benzene and benzenedithiol derivatives are discussed on the basis of a qualitative Hückel molecular orbital analysis for better understanding of the effect of anchoring sulfur atoms. A recent work for the orbital control of electron transport through aromatic hydrocarbons provided an important concept for the design of high-conductance connections of a molecule with anchoring atoms. In this work the origin of the frontier orbitals of benzenedithiol derivatives, the effect of the sulfur atoms on the orbitals and on the electron transport properties, and the applicability of the theoretical concept on aromatic hydrocarbons with the anchoring units are studied. The results demonstrate that the orbital view predictions are applicable to molecules perturbed by the anchoring units. The electron transport properties of benzene are found to be qualitatively consistent with those of benzenedithiol with respect to the site dependence. To verify the result of the Hückel molecular orbital calculations, fragment molecular orbital analyses with the extended Hückel molecular orbital theory and electron transport calculations with density functional theory are performed. Calculated results are in good agreement with the orbital interaction analysis. The phase, amplitude, and spatial distribution of the frontier orbitals play an essential role in the design of the electron transport properties through aromatic hydrocarbons.

Orbital Views on Electron-Transport Properties of Cyclophanes: Insight into Intermolecular Transport

“…We have succeeded in applying the orbital symmetry rule to small-size aromatic hydrocarbons, 48 PAHs with different molecular sizes and edge type structures, 49 photoswitching systems, 50 and strong-coupled molecules with the electrodes. 52 According to the orbital analysis of the phase and amplitude of the HOMO and LUMO, we could easily predict possible connections and choose favorable atoms of the molecule to connect with electrodes for effective electron transport.…”

“…48,49 Recently site-specific electron-transport phenomena are discussed on the basis of a qualitative molecular orbital analysis for better understanding of the effect of anchoring sulfur atoms. 52 MOs perturbed by the anchoring sulfur atoms still keep the electronhole symmetry, in particular combination of symmetry in the HOMO and LUMO.…”

Single-Molecule Phenyl-Acetylene-Macrocycle-Based Optoelectronic Switch Functioning as a Quantum-Interference-Effect Transistor

“…Recently, DQI has been experimentally observed in electron transport through a cross-conjugated molecular junction at room temperature [12]. Many theoretical studies on DQI involve ring-shaped conjugated molecules [4,[18][19][20][21][22][23] or cross-conjugated molecules [24] due to their simple electronic structure and the proximity of their anti-resonant states to the Fermi level of the electrodes. Moreover, ab initio calculations indicate that large conjugated molecules can enhance π-electron tunneling and suppress σ-electron tunneling [20].…”

A new approach to the method of source-sink potentials for molecular conduction

“…42,53 It was observed that the predicted Fermi-level conduction of a molecule with bipartite molecular graph and a non-zero HOMO-LUMO gap (specifically a Kekulean benzenoid) is large when both HOMO and LUMO have entries of large magnitude on both connection vertices (ourL andR) and the product of entries is of opposite sign for HOMO and LUMO. By the pairing theorem, this latter requirement implies that the connection vertices are in different partite sets.…”

“…4. perturbation treatment of T(0) (for all non-ipso devices based on bipartite molecular graphs), as used in other theories of orbital contributions. 16,42,53 …”