Anodic Methods for Covalent Attachment of Ethynylferrocenes to Electrode Surfaces

Comparison of Ethynyl Activation Processes

Matthew V. Sheridan, Kevin Lam, Mona Sharafi, Severin T. Schneebeli, William E. Geiger

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The electrochemical oxidation of ferrocenes having an H- or Li-terminated ethynyl group has been studied, especially as it relates to their covalent anchoring to carbon surfaces. The anodic oxidation of lithioethynylferrocene (1-Li) results in rapid loss of Li+ and formation of the ethynyl-based radical FeCp(η5-C5H4)(C≡C), (1, Cp = η5-C5H5), which reacts with the electrode. Chemically modified electrodes (CMEs) were thereby produced containing strongly bonded, ethynyl-linked monolayers and electrochemically controlled multilayers. Strong attachments of ethynylferrocenes to gold and platinum surfaces were also possible. The lithiation/anodic oxidation process is a mirror analogue of the diazonium/cathodic reduction process for preparation of aryl-modified CMEs. A second method produced an ethynylferrocene-modified electrode by direct anodic oxidation of the H-terminated ethynylferrocene (1-H) at a considerably more positive potential. Both processes produced robust modified electrodes with well-defined ferrocene-based surface cyclic voltammetry waves that remained unchanged for as many as 104 scans. Ferrocene derivatives in which the ethynyl moiety was separated from the cyclopentadienyl ring by an ether group showed very similar behavior. DFT calculations were performed on the relevant redox states of 1-H, 1-Li, and 1, with emphasis on the ferrocenyl vs ethynyl character of their high valence orbitals. Whereas the HOMOs of both 1-H and 1-Li have some ethynyl character, the SOMOs of the corresponding monocations are strictly ferrocenium in makeup. Predominant ethynyl character returns to the highest valence orbitals after loss of Li+ from [1-Li]+ or loss of H+ from [1-H]2+. These anodic processes hold promise for the controlled chemical modification of carbon and other electrode surfaces by a variety of ethynyl or alkynyl-linked organic and metal-containing systems.

Original languageEnglish
Pages (from-to)1645-1657
Number of pages13
JournalLangmuir
Volume32
Issue number6
DOIs
Publication statusPublished - Feb 16 2016
Externally publishedYes

Fingerprint

attachment
Chemical activation
activation
Electrodes
electrodes
Anodic oxidation
oxidation
Carbon
ferrocenes
valence
orbitals
electrochemical oxidation
Electrochemical oxidation
carbon
Chemical modification
Platinum
Discrete Fourier transforms
Gold
Ether
Cyclic voltammetry

ASJC Scopus subject areas

  • Electrochemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Materials Science(all)
  • Spectroscopy

Cite this

Anodic Methods for Covalent Attachment of Ethynylferrocenes to Electrode Surfaces : Comparison of Ethynyl Activation Processes. / Sheridan, Matthew V.; Lam, Kevin; Sharafi, Mona; Schneebeli, Severin T.; Geiger, William E.

In: Langmuir, Vol. 32, No. 6, 16.02.2016, p. 1645-1657.

Research output: Contribution to journalArticle

Sheridan, Matthew V. ; Lam, Kevin ; Sharafi, Mona ; Schneebeli, Severin T. ; Geiger, William E. / Anodic Methods for Covalent Attachment of Ethynylferrocenes to Electrode Surfaces : Comparison of Ethynyl Activation Processes. In: Langmuir. 2016 ; Vol. 32, No. 6. pp. 1645-1657.
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