IR spectroscopic characterization of SAMs made from a homologous series of pyridine disulfides

A homologous series of pyridine-terminated organic disulfides has been used to prepare self-assembled monolayers (SAMs) of the corresponding thiolates on Au substrates. A characterization using IR-spectroscopy reveals surprisingly large differences between the members of the homologous series. We find a strong evidence for partial protonation of the pyridine-terminated organic surfaces exposed by the corresponding SAMs in particular in the case where the SH-group is directly attached to the pyridine ring. The assignment of the vibrational frequencies is based on ab initio calculations for the investigated thiol monomers. (C) 2009 Elsevier B.V. All rights reserved.