High-Conductive Organometallic Molecular Wires with Delocalized Electron Systems Strongly Coupled to Metal Electrodes

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• 作者：Florian Schwarz ; Georg Kastlunger ; Franziska Lissel ; Heike Riel ; Koushik Venkatesan ; Heinz Berke ; Robert Stadler ; Emanuel L枚rtscher
• 刊名：Nano Letters
• 出版年：2014
• 出版时间：October 8, 2014
• 年：2014
• 卷：14
• 期：10
• 页码：5932-5940
• 全文大小：645K
• ISSN：1530-6992

文摘

Besides active, functional molecular building blocks such as diodes or switches, passive components, for example, molecular wires, are required to realize molecular-scale electronics. Incorporating metal centers in the molecular backbone enables the molecular energy levels to be tuned in respect to the Fermi energy of the electrodes. Furthermore, by using more than one metal center and sp-bridging ligands, a strongly delocalized electron system is formed between these metallic 鈥渄opants鈥? facilitating transport along the molecular backbone. Here, we study the influence of molecule鈥搈etal coupling on charge transport of dinuclear X(PP)₂FeC₄Fe(PP)₂X molecular wires (PP = Et₂PCH₂CH₂PEt₂); X = CN (1), NCS (2), NCSe (3), C₄SnMe₃ (4), and C₂SnMe₃ (5) under ultrahigh vacuum and variable temperature conditions. In contrast to 1, which showed unstable junctions at very low conductance (8.1 脳 10^鈥? G₀), 4 formed a Au鈥揅₄FeC₄FeC₄鈥揂u junction 4鈥?after SnMe₃ extrusion, which revealed a conductance of 8.9 脳 10^鈥? G₀, 3 orders of magnitude higher than for 2 (7.9 脳 10^鈥? G₀) and 2 orders of magnitude higher than for 3 (3.8 脳 10^鈥? G₀). Density functional theory (DFT) confirmed the experimental trend in the conductance for the various anchoring motifs. The strong hybridization of molecular and metal states found in the C鈥揂u coupling case enables the delocalized electronic system of the organometallic Fe₂ backbone to be extended over the molecule鈥搈etal interfaces to the metal electrodes to establish high-conductive molecular wires.

Keywords:

Molecular Wire; Single-Molecule Junctions; Electronic Transport; Break-Junctions; Organometallic Compounds; Density Functional Theory