Infrared spectroelectrochemical characterization of ferrocene-terminated alkanethiolate monolayers at gold

Journal Article · Thu Oct 01 00:00:00 EDT 1992 · Langmuir; (United States)

DOI:https://doi.org/10.1021/la00046a028· OSTI ID:5425008

Popenoe, D D; Deinhammer, R S; Porter, M D ^[1]

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1. Ames Lab., IA (United States) Iowa State Univ., Ames, IA (United States)

Cyclic voltammetry and in situ infrared reflection-absorption spectroscopy with electrochemical modulation were applied to the study of monolayers self-assembled from 11-mercaptoundecyl ferrocene-carboxylate (FcCOOC[sub 11]SH) at gold. Voltammetry was used to assess both the reactivity and stability of the surface film in various aqueous electrolytes. The results of these studies indicated that the ferrocenyl monolayers are relatively unstable at pH > 2, except when perchlorate is the dominant anion present. A large change in double-layer capacitance observed upon oxidation of the ferrocenyl end group was attributed to the creation of cationic sites in the diffuse layer. Compositional and structural correlations between the monolayer and the redox chemistry of the ferrocenyl end group were probed using the in situ spectroscopic technique. The features observed in the differential spectra of the oxidized form of the film were ascribed to changes in the bond strengths of the adsorbate as a result of generation of a ferricinium ion. No detectable changes in orientation of the polymethylene chains as a function of applied voltage were observed. The spectral data also suggest that the redox chemistry leads to a reorientation of the water molecules in the region near the ferrocenyl end group. Vibrational mode assignments for FcCOOC[sub 11]SH, based on studies of several analogs with different alkoxy groups, are presented along with infrared spectra and band assignments for several isotopically labeled ferrocenyl esters (i.e., ethyl ferrocenecarboxylate, ethyl-d[sub 5] ferrocenecarboxylate, and 2-(dimethylamino)ethyl ferrocenecarboxylate). 55 refs., 7 figs., 2 tabs.

• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5425008
• Journal Information: Langmuir; (United States), Vol. 8:10; ISSN 0743-7463
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
GOLD
SURFACE PROPERTIES
ORGANIC SULFUR COMPOUNDS
ADSORPTION
INFRARED SPECTRA
ELECTROCHEMISTRY
FERROCENE
REDOX REACTIONS
THIN FILMS
VOLTAMETRY
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DIENES
ELEMENTS
FILMS
HYDROCARBONS
IRON COMPLEXES
METALS
ORGANIC COMPOUNDS
POLYENES
SORPTION
SPECTRA
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
400102 - Chemical & Spectral Procedures