Effect of Metal Complexation on the Conductance of Single-Molecular Wires Measured at Room Temperature

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• 作者：Julia Ponce ; Carlos R. Arroyo ; Sergio Tatay ; Riccardo Frisenda ; Pablo Gavi帽a ; Daniel Aravena ; Eliseo Ruiz ; Herre S. J. van der Zant ; Eugenio Coronado
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：June 11, 2014
• 年：2014
• 卷：136
• 期：23
• 页码：8314-8322
• 全文大小：429K
• 年卷期：v.136,no.23(June 11, 2014)
• ISSN：1520-5126

文摘

The present work aims to give insight into the effect that metal coordination has on the room-temperature conductance of molecular wires. For that purpose, we have designed a family of rigid, highly conductive ligands functionalized with different terminations (acetylthiols, pyridines, and ethynyl groups), in which the conformational changes induced by metal coordination are negligible. The single-molecule conductance features of this series of molecular wires and their corresponding Cu(I) complexes have been measured in break-junction setups at room temperature. Experimental and theoretical data show that no matter the anchoring group, in all cases metal coordination leads to a shift toward lower energies of the ligand energy levels and a reduction of the HOMO鈥揕UMO gap. However, electron-transport measurements carried out at room temperature revealed a variable metal coordination effect depending on the anchoring group: upon metal coordination, the molecular conductance of thiol and ethynyl derivatives decreased, whereas that of pyridine derivatives increased. These differences reside on the molecular levels implied in the conduction. According to quantum-mechanical calculations based on density functional theory methods, the ligand frontier orbital lying closer to the Fermi energy of the leads differs depending on the anchoring group. Thereby, the effect of metal coordination on molecular conductance observed for each anchoring could be explained in terms of the different energy alignments of the molecular orbitals within the gold Fermi level.