Interfacial Electron-Transfer Kinetics of Ferrocene through Oligophenyleneethynylene Bridges Attached to Gold Electrodes as Constituents of Self-Assembled Monolayers: Observation of a Nonmonotonic Dis

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• 作者：John F. Smalley ; Sandra B. Sachs ; Christopher E. D. Chidsey ; Stephen P. Dudek ; Hadley D. Sikes ; Stephen E. Creager ; C. J. Yu ; Stephen W. Feldberg ; and Marshall D. Newton
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：November 10, 2004
• 年：2004
• 卷：126
• 期：44
• 页码：14620 - 14630
• 全文大小：295K
• 年卷期：v.126,no.44(November 10, 2004)
• ISSN：1520-5126

文摘

The standard heterogeneous electron-transfer rate constants (k_n⁰) between substrate goldelectrodes and the ferrocene redox couple attached to the electrode surface by variable lengths of substitutedor unsubstituted oligophenyleneethynylene (OPE) bridges as constituents of mixed self-assembledmonolayers were measured as a function of temperature. The distance dependences of the unsubstitutedOPE standard rate constants and of the preexponential factors (A_n) obtained from an Arrhenius analysisof the unsubstituted OPE k_n⁰ versus temperature data are not monotonic. This surprising result, togetherwith the distance dependence of the substituted OPE preexponential factors, may be assessed in terms ofthe likely conformational variability of the OPE bridges (as a result of the low intrinsic barrier to rotation ofthe phenylene rings in these bridges) and the associated sensitivity of the rate of electron transfer (and,hence, the single-molecule conductance which may be estimated using A_n) through these bridges to theconformation of the bridge. Additionally, the measured standard rate constants were independent of theidentity of the diluent component of the mixed monolayer, and using an unsaturated OPE diluent has noeffect on the rate of electron transfer through a long-chain alkanethiol bridge. These observations indicatethat the diluent does not participate in the electron-transfer event.