Journal of Electroanalytical Chemistry, Vol.621, No.2, 159-170, 2008
Self-assembled monolayers of ruthenocene-substituted biphenyl ethynyl thiols on gold
Ruthenocene is a promising electrochemical agent and it potential one-electron reservoir with a stable and irreversible redox system. to this respect, two new molecules, Rc-C C-C6H4-C6H4-SAc (REBTA) and Rc-C C-C6H4-C6H6-SH (REBTH) (Rc = (eta(5)-C5H5)Ru(eta(5)-C5H4): Ac =C(O)Me) were synthesized. The single crystal structure of REBTA was determined, showing that this compound forms a 3D-network structure set-up by pi-pi interactions of C6H4/C6H4 and C6H4/C5H5 units. Cyclic voltammetric measurements were carried out with REBTA, REBTH, and Rc-C CH for comparison. In view of possible electrochemical applications, REBTH and REBTH were used to prepare self-assembled monolayers (SAMs) on Au(1 1 1) substrates. The resulting SAMs were characterized by high-resolution X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. The films were found to be well-ordered and densely packed, even though with a lover density than the analogous films formed from similar ferrocene-substituted molecules, which can be explained by the somewhat larger volume of the ruthenocene moiety, hindering the molecular packing. The presence of the acetyl protection group did not affect the quality of the resulting films significantly, even though some differences between the individual SAMs were found, dependent oil the deprotection agent or its absence in the primary solution. The protection group was completely removed in all cases, even when no deprotection agent was used. (c) 2007 Elsevier B.V. All rights reserved.
Keywords:Metallocenes;Redox system;Self-assembled monolayers;Cyclic voltammetry;X-ray photoelectron spectroscopy;Near-edge X-ray absorption fine structure spectroscopy