Alkane-tetrathiol induced formation of remarkably stable self-assembled monolayer and polymer films containing electroactive tetrathiafulvalene moieties on metal electrodes

Abstract

Remarkably stable self-assembled monolayer and polymer films composed of a new tetrathiafulvalenyl-tetrathiol have been formed on metal electrodes: this is a new class of surface modification by self-assembly and electrochemical polymerization using the same alkane-tetrathiol.

References

1. Molecular Design of Electrode Surfaces, ed. R. W. Murray, Wiley-Interscience, New York, 1992.
2. A. Ulman, An Introduction to Ultrathin Organic Films, Academic Press, Inc., Boston, MA, 1991.
3. L. H. Dubois and R. G. Nuzzo, Annu, Rev. Phys. Chem., 1992, 43, 437; A. Ulman, Chem. Rev., 1996, 96, 1533.
4. A. Deronzier and J. C. Moutet, Acc. Chem. Res., 1989, 22, 249; J. Roncali, Chem. Rev., 1992, 92, 711.
5. 1: FTIR 2554 cm^–1(SH); ¹H NMR (CDCl₃)δ 1.39 (t, 4H, J 8.1 Hz, SH), 1.94 (q, 8H, J 6.8 Hz, CH₂), 2.69 (dt, 8H, J 8.1, 6.8 Hz, CH₂SH), 2.96 (t, 8H, J 6.8 Hz, SCH₂); ¹³C NMR (CDCl₃)δ 23.0, 33.3, 34.5, 110.5, 127.9. Exact mass: calc. for C₁₈H₂₈S₁₂: 627.8840. Found: 627.8856. 2: FTIR 2557 cm^–1(SH); ¹H NMR (CDCl₃)δ 1.37 (t, 1H, J 8.0 Hz, SH), 1.93 (q, 2H, J 7.0 Hz, CH₂), 2.65 (dt, 2H, J 8.0, 7.0 Hz, CH₂SH), 2.87 (t, 2H, J 7.0 Hz, SCH₂), 6.32 (s, 2H, C=CH), 6.37 (s, 1H, C=CH); ¹³C NMR (CDCl₃)δ 22.9, 33.2, 34.0, 109.4, 112.9, 118.9, 119.0, 122.9, 126.6. MS, m/z 310 (M⁺). The synthesis of 1, 2 and related compounds will be reported elsewhere.
6. Most electrochemical studies of self-assembled monolayers carried out to date have used aqueous media. The properties of self-assembled monolayers in organic solvents have been discussed: K. A. Groat and S. E. Creager, Langmuir, 1993, 9, 3668 and references therein.
7. The tetramethylsulfide of 1 did not polymerize upon repeated electrochemical oxidation. This result indicates that the tetrathiol needs to form polymer films for this to occur.
8. The polymerization may proceed via the formation of disulfide linkages upon oxidation of the thiol groups of 1. Mechanistic studies for the electropolymerization of tetrathiol 1 are in progress.
9. The surface coverage of the polymer films on the electrode can be controlled by cycling times.
10. Although there have been numerous investigations into the electro-polymerization of pyrrole- and thiophene-based monomers, the mechanism for the deposition of these films on electrode surfaces is not well defined.⁴.