“Chain-Like” Trimetallic Ruthenium Complexes with C7 Carbon-Rich Bridges: Experimental and Theoretical Investigations of Electronic Communication Tuning in Five Distinct Oxidati

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• 作者：Cline Olivier ; Karine Costuas ; Sylvie Choua ; Vincent Maurel ; Philippe Turek ; Jean-Yves Saillard ; Daniel Touchard ; Stphane Rigaut
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：April 28, 2010
• 年：2010
• 卷：132
• 期：16
• 页码：5638-5651
• 全文大小：584K
• 年卷期：v.132,no.16(April 28, 2010)
• ISSN：1520-5126

文摘

In this work, we report the synthesis and the electronic properties of the unique highly conjugated molecular wires trans-[Cl−(dppe)₂Ru═C═C═(Ph)C−CH═(CH₃)C−C≡C−(X)₂Ru−C≡C−C(CH₃)═CH−C(Ph)═C═C═Ru(dppe)₂Cl]ⁿ⁺ (n = 2, X = dppe ([3a](OTf)₂) and dppm ([3b](OTf)₂) with three similar metal centers spanned by two odd-numbered unsaturated C₇ chains providing a 28 Å long conjugated path and displaying five well-separated redox states (n = 0−4). Successive one-electron transfer steps were studied by means of cyclic voltammetry, EPR and UV−vis−NIR−IR spectroelectrochemistry. The electronic and physical properties of the different states were further rationalized with the help of DFT-based calculations. Upon one-electron reduction (n = 1), the single electron is delocalized over the two carbon chains through the central metal atom to an extent driven by the rotations within and between the chains. The second reduction (n = 0) involves the whole carbon-rich conjugated path of the molecule in a spin polarized scheme: one electron is delocalized over each chain, and the two electrons are antiferromagnetically coupled with a coupling on the order of kT. Interestingly, oxidation processes strongly involve both the metal atoms and the bridging ligands. The combined investigations reveal that the mono-oxidized system (n = 3) presents a spin density uniformly distributed between the metal atoms and the carbon atoms of the chains, whereas in the second oxidation state (n = 4) the compounds show a strong antiferromagnetic coupling on the order of 4 kT between the two single electrons localized in two distinct delocalized spin orbitals implying all the carbon atoms of the bridges and the three metal atoms. Thus, for the first time, electronic communication was fully evidenced and tuned in homonuclear trimetallic oligomeric carbon-rich systems in either an oxidation or a reduction process.