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Insulated molecular wires: inhibiting orthogonal contacts in metal complex based molecular junctions

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Title: Insulated molecular wires: inhibiting orthogonal contacts in metal complex based molecular junctions
Authors: Al-Owaedi, OA
Bock, S
Milan, DC
Oerthel, M-C
Inkpen, MS
Yufit, DS
Sobolev, AN
Long, NJ
Albrecht, T
Higgins, SJ
Bryce, MR
Nichols, RJ
Lambert, CJ
Low, PJ
Item Type: Journal Article
Abstract: Metal complexes are receiving increased attention as molecular wires in fundamental studies of the transport properties of metal|molecule|metal junctions. In this context we report the single-molecule conductance of a systematic series of d8 square-planar platinum(II) trans-bis(alkynyl) complexes with terminal trimethylsilylethynyl (C[triple bond, length as m-dash]CSiMe3) contacting groups, e.g. trans-Pt{C[triple bond, length as m-dash]CC6H4C[triple bond, length as m-dash]CSiMe3}2(PR3)2 (R = Ph or Et), using a combination of scanning tunneling microscopy (STM) experiments in solution and theoretical calculations using density functional theory and non-equilibrium Green's function formalism. The measured conductance values of the complexes (ca. 3–5 × 10−5G0) are commensurate with similarly structured all-organic oligo(phenylene ethynylene) and oligo(yne) compounds. Based on conductance and break-off distance data, we demonstrate that a PPh3 supporting ligand in the platinum complexes can provide an alternative contact point for the STM tip in the molecular junctions, orthogonal to the terminal C[triple bond, length as m-dash]CSiMe3 group. The attachment of hexyloxy side chains to the diethynylbenzene ligands, e.g. trans-Pt{C[triple bond, length as m-dash]CC6H2(Ohex)2C[triple bond, length as m-dash]CSiMe3}2(PPh3)2 (Ohex = OC6H13), hinders contact of the STM tip to the PPh3 groups and effectively insulates the molecule, allowing the conductance through the full length of the backbone to be reliably measured. The use of trialkylphosphine (PEt3), rather than triarylphosphine (PPh3), ancillary ligands at platinum also eliminates these orthogonal contacts. These results have significant implications for the future design of organometallic complexes for studies in molecular junctions.
Issue Date: 28-Jul-2017
Date of Acceptance: 25-Jun-2017
URI: http://hdl.handle.net/10044/1/52957
DOI: https://dx.doi.org/10.1039/c7nr01829k
ISSN: 2040-3364
Publisher: Royal Society of Chemistry
Start Page: 9902
End Page: 9912
Journal / Book Title: Nanoscale
Volume: 9
Issue: 28
Copyright Statement: This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Keywords: Science & Technology
Physical Sciences
Technology
Chemistry, Multidisciplinary
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Physics, Applied
Chemistry
Science & Technology - Other Topics
Materials Science
Physics
SP CARBON CHAINS
SCANNING-TUNNELING-MICROSCOPY
SELF-ASSEMBLED MONOLAYERS
LOW-SYMMETRY DISTORTIONS
2 P(CH2)(M)P LINKAGES
CHARGE-TRANSPORT
ELECTRON-TRANSPORT
PT(CC)(N)PT MOIETIES
LENGTH DEPENDENCE
DOUBLE HELICES
10 Technology
02 Physical Sciences
03 Chemical Sciences
Publication Status: Published
Appears in Collections:Chemistry
Catalysis and Advanced Materials
Faculty of Natural Sciences



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