Chemical routes to molecular SAMs on H-Si(100) with distinct and well-defined redox potentials

New or rarely reported synthetic routes have been applied to produce electroactive hybrid materials from ferrocene (Fc) derivatives with a known and pre-established variation in the tethering arm bound to Si. The series is characterized for having the shortest molecular link for a direct covalent attachment to H-terminated Si(100). Grignard derivatization, Lewis acid catalysis and nucleophilic substitution by an acetilyde anion have been applied for the first time in order to obtain the full series of possible unsaturations in the C-C lateral chain bound to Si: ethyl (EtFC/Si), vinyl (VFC/Si) and ethynyl group (EFC/Si). The redox potentials of these three molecule/surface hybrids, measured by cyclic voltammetry, are respectively 0.059, 0.136 and 0.251 V vs. Ag/Ag+, and increase with the extent of unsaturation in the tethering arm. XPS and electrochemical measurements have been used to assess the chemical nature and electronic properties of the hybrids.