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Robust Self‐Assembled Monolayers of Ru II and Os II Polypyridines on Gold Surfaces: Exploring New Potentials
Author(s) -
Murphy Frances A.,
Suárez Stéphane,
Figgemeier Egbert,
Schofield Emma R.,
Draper Sylvia M.
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801930
Subject(s) - terpyridine , piperazine , monolayer , dithiocarbamate , chemistry , redox , ligand (biochemistry) , denticity , cyclic voltammetry , electrochemistry , ruthenium , crystallography , self assembled monolayer , metal , photochemistry , inorganic chemistry , electrode , organic chemistry , catalysis , crystal structure , biochemistry , receptor
Functional monolayers : Ru II and Os II bis‐terpyridine complexes have been attached through a piperazine‐supported dithiocarbamate to a gold substrate (see picture). The robust tether, and the favourable reduction in oxidation potential induced by the electron‐rich piperazine result in self‐assembled monolayers with excellent reversible redox behaviour and exceptional stability.Metal complexes [M(phtpy)(pztpy)](PF 6 ) 2 (phtpy=4′‐phenyl‐2,2′:6′,2′′‐terpyridine, pztpy=4′‐( N ‐piperazinyl)‐2,2′:6′,2′′‐terpyridine, M=Ru, Os) were prepared and examined spectroscopically and electrochemically. The piperazine attachment was found to significantly modify the photophysical and electrochemical properties compared to the parent bis‐terpyridine complexes, causing a red‐shift of the 1 MLCT (23 nm, 53.9 eV) and a substantial cathodic shift of the redox potential (0.3 V for Ru, 0.23 V for Os). Self‐assembled monolayers (SAMs) of the complexes on polished gold electrodes were generated simply by the in situ formation of a dithiocarbamate (DTC) anchoring group at the terminal piperazinyl nitrogen on the pztpy ligand. Cyclic voltammetry revealed that the monolayers show excellent reversible behaviour and exceptional stability. The high stability of the SAMs is attributed to the strong bidentate attachment to the gold surface of the DTC tether and the favourable low oxidation potentials of the complexes which result from the electron‐rich piperazine nitrogen on the pztpy ligand. Such DTC‐based SAMs demonstrate a substantial improvement over commonly‐employed thiol‐based systems, and offer new scope for future development.