Al-Owaedi, Oday A, Bock, Soren, Milan, David C 
ORCID: 0000-0002-2077-7920, Oerthel, Marie-Christine, Inkpen, Michael S, Yufit, Dmitry S, Sobolev, Alexandre N, Long, Nicholas J, Albrecht, Tim, Higgins, Simon J ORCID: 0000-0003-3518-9061 et al (show 4 more authors)
(2017)
Insulated molecular wires: inhibiting orthogonal contacts in metal complex based molecular junctions.
NANOSCALE, 9 (28).
pp. 9902-9912.
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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 d<sup>8</sup> square-planar platinum(ii) trans-bis(alkynyl) complexes with terminal trimethylsilylethynyl (C[triple bond, length as m-dash]CSiMe<sub>3</sub>) contacting groups, e.g. trans-Pt{C[triple bond, length as m-dash]CC<sub>6</sub>H<sub>4</sub>C[triple bond, length as m-dash]CSiMe<sub>3</sub>}<sub>2</sub>(PR<sub>3</sub>)<sub>2</sub> (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<sup>-5</sup>G<sub>0</sub>) 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 PPh<sub>3</sub> 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]CSiMe<sub>3</sub> group. The attachment of hexyloxy side chains to the diethynylbenzene ligands, e.g. trans-Pt{C[triple bond, length as m-dash]CC<sub>6</sub>H<sub>2</sub>(Ohex)<sub>2</sub>C[triple bond, length as m-dash]CSiMe<sub>3</sub>}<sub>2</sub>(PPh<sub>3</sub>)<sub>2</sub> (Ohex = OC<sub>6</sub>H<sub>13</sub>), hinders contact of the STM tip to the PPh<sub>3</sub> groups and effectively insulates the molecule, allowing the conductance through the full length of the backbone to be reliably measured. The use of trialkylphosphine (PEt<sub>3</sub>), rather than triarylphosphine (PPh<sub>3</sub>), 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.
| Item Type: | Article |
|---|---|
| Depositing User: | Symplectic Admin |
| Date Deposited: | 06 Oct 2017 10:39 |
| Last Modified: | 19 Jan 2023 06:53 |
| DOI: | 10.1039/c7nr01829k |
| Related URLs: | |
| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3009813 |
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