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Conductance Modulation in an α-Terthiophene Molecular Junction Characterized by Surface-Enhanced Raman Scattering. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2022. [DOI: 10.1380/ejssnt.2023-004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Senthil Kumar K, Šalitroš I, Heinrich B, Moldovan S, Mauro M, Ruben M. Spin-crossover in iron(II)-phenylene ethynylene-2,6-di(pyrazol-1-yl) pyridine hybrids: toward switchable molecular wire-like architectures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:204002. [PMID: 31945748 DOI: 10.1088/1361-648x/ab6cc2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Luminescent oligo(p-phenylene ethynylene) (OPE) and spin-crossover (SCO) active Fe(II)-2,6-di(pyrazol-1-yl) pyridine (BPP) systems are prominent examples proposed to develop functional materials such as molecular wires/memories. A marriage between OPE and Fe(II)-BPP systems is a strategy to obtain supramolecular luminescent ligands capable of metal coordination useful to produce novel spin-switchable hybrids with synergistic coupling between spin-state of Fe(II) and a physical property associated with the OPE skeleton, for example, electronic conductivity or luminescence. To begin in this direction, two novel ditopic ligands, namely L1 and L2, featuring OPE-type backbone end-capped with metal coordinating BPP were designed and synthetized. The ligand L2 tailored with 2-ethylhexyloxy chains at the 2 and 5 positions of the OPE skeleton shows modulated optical properties and improved solubility in common organic solvents relative to the parent ligand L1. Solution phase complexation of L1 and L2 with Fe(BF4)2·6H2O resulted in the formation of insoluble materials of the composition [Fe(L1)] n (BF4)2n and [Fe(L2)] n (BF4)2n as inferred from elemental analyses. Complex [Fe(L1)] n (BF4)2n underwent thermal SCO centred at T 1/2 = 275 K as well as photoinduced low-spin to high-spin transition with the existence of the metastable high-spin state up to 52 K. On the other hand, complex [Fe(L2)] n (BF4)2n , tethered with 2-ethylhexyloxy groups, showed gradual and half-complete SCO with 50% of the Fe(II)-centres permanently blocked in the high-spin state due to intermolecular steric interactions. The small angle x-ray scattering (SAXS) pattern of the as-prepared solid complex [Fe(L1)] n (BF4)2n revealed the presence of nm-sized crystallites implying a possible methodology towards the template-free synthesis of functional-SCO nanostructures.
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Affiliation(s)
- Kuppusamy Senthil Kumar
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS-Université de Strasbourg, 23, rue du Loess, BP 43, 67034 Strasbourg cedex 2, France
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Wang K, Vezzoli A, Grace IM, McLaughlin M, Nichols RJ, Xu B, Lambert CJ, Higgins SJ. Charge transfer complexation boosts molecular conductance through Fermi level pinning. Chem Sci 2019; 10:2396-2403. [PMID: 30881668 PMCID: PMC6385675 DOI: 10.1039/c8sc04199g] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 01/02/2019] [Indexed: 11/21/2022] Open
Abstract
Interference features in the transmission spectra can dominate charge transport in metal-molecule-metal junctions when they occur close to the contact Fermi energy (E F). Here, we show that by forming a charge-transfer complex with tetracyanoethylene (TCNE) we can introduce new constructive interference features in the transmission profile of electron-rich, thiophene-based molecular wires that almost coincide with E F. Complexation can result in a large enhancement of junction conductance, with very efficient charge transport even at relatively large molecular lengths. For instance, we report a conductance of 10-3 G 0 (∼78 nS) for the ∼2 nm long α-quaterthiophene:TCNE complex, almost two orders of magnitude higher than the conductance of the bare molecular wire. As the conductance of the complexes is remarkably independent of features such as the molecular backbone and the nature of the contacts to the electrodes, our results strongly suggest that the interference features are consistently pinned near to the Fermi energy of the metallic leads. Theoretical studies indicate that the semi-occupied nature of the charge-transfer orbital is not only important in giving rise to the latter effect, but also could result in spin-dependent transport for the charge-transfer complexes. These results therefore present a simple yet effective way to increase charge transport efficiency in long and poorly conductive molecular wires, with important repercussions in single-entity thermoelectronics and spintronics.
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Affiliation(s)
- Kun Wang
- Department of Physics and Astronomy & NanoSEC , University of Georgia , 220 Riverbend Road , Athens , GA 30602 , USA .
| | - Andrea Vezzoli
- Department of Chemistry , University of Liverpool , Crown Street , Liverpool L69 7ZD , UK .
| | - Iain M Grace
- Department of Physics , Lancaster University , Lancaster LA1 4YB , UK .
| | - Maeve McLaughlin
- Department of Chemistry , University of Liverpool , Crown Street , Liverpool L69 7ZD , UK .
| | - Richard J Nichols
- Department of Chemistry , University of Liverpool , Crown Street , Liverpool L69 7ZD , UK .
| | - Bingqian Xu
- Department of Physics and Astronomy & NanoSEC , University of Georgia , 220 Riverbend Road , Athens , GA 30602 , USA .
- College of Engineering & NanoSEC , University of Georgia , 220 Riverbend Road , Athens , GA 30602 , USA
| | - Colin J Lambert
- Department of Physics , Lancaster University , Lancaster LA1 4YB , UK .
| | - Simon J Higgins
- Department of Chemistry , University of Liverpool , Crown Street , Liverpool L69 7ZD , UK .
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Evers F, Venkataraman L. Preface: Special Topic on Frontiers in Molecular Scale Electronics. J Chem Phys 2017. [DOI: 10.1063/1.4977469] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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