Jump to main content
Jump to site search

Issue 14, 2018
Previous Article Next Article

Understanding the charge transport properties of redox active metal–organic conjugated wires

Author affiliations

Abstract

Layer-by-layer assembly of the dirhodium complex [Rh2(O2CCH3)4] (Rh2) with linear N,N′-bidentate ligands pyrazine (LS) or 1,2-bis(4-pyridyl)ethene (LL) on a gold substrate has developed two series of redox active molecular wires, (Rh2LS)n@Au and (Rh2LL)n@Au (n = 1–6). By controlling the number of assembling cycles, the molecular wires in the two series vary systematically in length, as characterized by UV-vis spectroscopy, cyclic voltammetry and atomic force microscopy. The current–voltage characteristics recorded by conductive probe atomic force microscopy indicate a mechanistic transition for charge transport from voltage-driven to electrical field-driven in wires with n = 4, irrespective of the nature and length of the wires. Whilst weak length dependence of electrical resistance is observed for both series, (Rh2LL)n@Au wires exhibit smaller distance attenuation factors (β) in both the tunneling (β = 0.044 Å−1) and hopping (β = 0.003 Å−1) regimes, although in (Rh2LS)n@Au the electronic coupling between the adjacent Rh2 centers is stronger. DFT calculations reveal that these wires have a π-conjugated molecular backbone established through π(Rh2)–π(L) orbital interactions, and (Rh2LL)n@Au has a smaller energy gap between the filled π*(Rh2) and the empty π*(L) orbitals. Thus, for (Rh2LL)n@Au, electron hopping across the bridge is facilitated by the decreased metal to ligand charge transfer gap, while in (Rh2LS)n@Au the hopping pathway is disfavored likely due to the increased Coulomb repulsion. On this basis, we propose that the super-exchange tunneling and the underlying incoherent hopping are the dominant charge transport mechanisms for shorter (n ≤ 4) and longer (n > 4) wires, respectively, and the Rh2L subunits in mixed-valence states alternately arranged along the wire serve as the hopping sites.

Graphical abstract: Understanding the charge transport properties of redox active metal–organic conjugated wires

Back to tab navigation

Supplementary files

Publication details

The article was received on 01 Nov 2017, accepted on 16 Feb 2018 and first published on 19 Feb 2018


Article type: Edge Article
DOI: 10.1039/C7SC04727D
Citation: Chem. Sci., 2018,9, 3438-3450
  • Open access: Creative Commons BY license
  •   Request permissions

    Understanding the charge transport properties of redox active metal–organic conjugated wires

    D. Bu, Y. Xiong, Y. N. Tan, M. Meng, P. J. Low, D. Kuang and C. Y. Liu, Chem. Sci., 2018, 9, 3438
    DOI: 10.1039/C7SC04727D

    This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material.

    Reproduced material should be attributed as follows:

    • For reproduction of material from NJC:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the Centre National de la Recherche Scientifique (CNRS) and the RSC.
    • For reproduction of material from PCCP:
      [Original citation] - Published by the PCCP Owner Societies.
    • For reproduction of material from PPS:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC.
    • For reproduction of material from all other RSC journals:
      [Original citation] - Published by The Royal Society of Chemistry.

    Information about reproducing material from RSC articles with different licences is available on our Permission Requests page.

Search articles by author

Spotlight

Advertisements