Accession Number : ADA292754

Title :   Electron Transfer Kinetics of Self-Assembled Ferrocene C(12) Alkanethiol Monolayers on Gold Electrodes From 125K to 175K,

Descriptive Note : Interim rept.,

Corporate Author : NORTH CAROLINA UNIV AT CHAPEL HILL DEPT OF CHEMISTRY

Personal Author(s) : RICHARDSON, John N. ; Rowe, Gary K. ; Carter, Michael T. ; Tender, Leonard M. ; Curtin, Larry S.

PDF Url : ADA292754

Report Date : 23 MAR 1995

Pagination or Media Count : 34

Abstract : The electron transfer kinetics of monolayers of CpFeCpCO2(CH2)12SH and CH3(Ch2)11SH co-chemisorbed on gold electrodes have been measured in 2:1 (v:v) chloroethane/butyronitrile solvent at temperatures ranging from 125K to 175K with potential steps and cyclic voltammetry. Rate constants, k deg, measured using cyclic voltammetry range from 3x10(exp-4) to 10(exp-1)/s over these temperatures; an activation plot of logK DEG/K(SUB BETA)T(1/2) vs. 1/T gave Lambda = 0.89 eV for the reorganization energy for the Cp2Fe(+/0) reaction and a pre-factor of 6.5X10(exp 6) eV(-1)/s. The rate constants were obtained by comparison of experimental delta E PEAK values with those of cyclic voltammograms digitally simulated with Marcus-DOS theory. A value of Lambda = 0.76 eV is predicted from dielectric continuum theory. The CpFeCpCO2(CH2)12SH monolayers are kinetically inhomogeneous (disperse) as shown by nonlinear 1nI vs. time plots in potential step experiments. The kinetic dispersity has adverse effects on determinations of Lambda values from cyclic voltammetric waveshapes and from plots of potential step-derived rate constants, k( sub app,tau), against overpotential (eta), producing depressed values for Lambda. jg

Descriptors :   *ALKANES, *ELECTRODES, *KINETICS, *GOLD, *ELECTRON TRANSFER, *FERROCENES, ACTIVATION, DIELECTRICS, FILMS, RATES, CYCLES, REDUCTION, TIME, CONSTANTS, ADVERSE CONDITIONS, ORGANIC COMPOUNDS, VOLTAMMETRY, MOLECULAR PROPERTIES, PLOTTING, CHEMISORPTION, CARBONYL COMPOUNDS, CHLOROETHANES.

Subject Categories : Organic Chemistry
      Physical Chemistry
      Electricity and Magnetism
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE