Tuning the electrical conductance of metalloporphyrin supramolecular wires

• Published in: Scientific reports Vol. 6; no. 1; p. 37352
• Main Authors: Noori, Mohammed, Aragonès, Albert C., Di Palma, Giuseppe, Darwish, Nadim, Bailey, Steven W. D., Al-Galiby, Qusiy, Grace, Iain, Amabilino, David B., González-Campo, Arántzazu, Díez-Pérez, Ismael, Lambert, Colin J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.11.2016; Nature Publishing Group
• Subjects: 639/301/357/341; 639/925/927/998; Conductance; Copper; Electrical resistivity; Humanities and Social Sciences; Ions; Metal ions; Metals; multidisciplinary; Science; Short term memory; Thermodynamics; Zinc
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep37352

In contrast with conventional single-molecule junctions, in which the current flows parallel to the long axis or plane of a molecule, we investigate the transport properties of M(II)-5,15-diphenylporphyrin (M-DPP) single-molecule junctions (M=Co, Ni, Cu, or Zn divalent metal ions), in which the current flows perpendicular to the plane of the porphyrin. Novel STM-based conductance measurements combined with quantum transport calculations demonstrate that current-perpendicular-to-the-plane (CPP) junctions have three-orders-of-magnitude higher electrical conductances than their current-in-plane (CIP) counterparts, ranging from 2.10 −2 G 0 for Ni-DPP up to 8.10 −2 G 0 for Zn-DPP. The metal ion in the center of the DPP skeletons is strongly coordinated with the nitrogens of the pyridyl coated electrodes, with a binding energy that is sensitive to the choice of metal ion. We find that the binding energies of Zn-DPP and Co-DPP are significantly higher than those of Ni-DPP and Cu-DPP. Therefore when combined with its higher conductance, we identify Zn-DPP as the favoured candidate for high-conductance CPP single-molecule devices.