Abstract
The vibrational and H-1 NMR data hints that the coordination of the
2,2'-dithiodipyridine (2-pySS) ligand to the Ru(CN)(5)(3-) metal
center occurs through the sulfur atom instead of the nitrogen atoms
which is usually observed for N-heterocyclic ligands. Electrochemical
results show that this coordination mode implies an additional
thermodynamic stabilization of the Ru-II over Ru-III oxidation state due
to a relative stronger pi-back-bonding interaction with the empty
low-lying d pi orbitals of the sulfur atom. Computational data reinforce
the experimental results showing that the 2-pySS Lewis base centers are
located on the sulfur atoms. Ligands containing only sulfur atoms as
coordination sites (2,2'-dithiodipyridine N-oxide (2-pySSNO),
1,4-dithiane (1,4-dt), and 2,6-dithiaspiro3.3heptane (asp)) were
also coordinated to the Ru(CN)(5)(3-) metal center to undoubtedly
correlate the electrochemical results with the ligand coordination atom.
Among the synthesized compounds, the Ru(CN)5(1,4-dt)3- and
Ru(CN)5(asp)3- complexes showed to be able to form self-assembled
monolayers (SAMs) on gold. These SAMs, which were characterized by SERS
(surface-enhanced Raman scattering) spectroscopy, successfully assessed
the heterogeneous electron transfer reaction of the cytochrome c
metalloprotein in physiological medium. (c) 2007 Elsevier B.V. All
rights reserved.
Users
Please
log in to take part in the discussion (add own reviews or comments).