Multiredox Tetrathiafulvalene-Modified Oxide-Free Hydrogen-Terminated Si(100) Surfaces

Abstract

Tetrathiafulvalene (TTF) monolayers covalently bound to oxide-free hydrogen-terminated Si(100) surfaces have been prepared from the hydrosilylation reaction involving a TTF-terminated ethyne derivative. FTIR spectroscopy characterization using similarly modified porous Si(100) substrates revealed the presence of vibration bands assigned to the immobilized TTF rings and the Si–CC– interfacial bonds. Cyclic voltammetry measurements showed the presence of two reversible one-electron systems ascribed to TTF/TTF^.+ and TTF^.+/TTF²⁺ redox couples at ca. 0.40 and 0.75 V vs SCE, respectively, which compare well with the values determined for the electroactive molecule in solution. The amount of immobilized TTF units could be varied in the range from 1.7 × 10^–10 to 5.2 × 10^–10 mol cm^–2 by diluting the TTF-terminated chains with inert <i>n</i>-decenyl chains. The highest coverage obtained for the single-component monolayer is consistent with a densely packed TTF monolayer