One-step vs stepwise immobilization of 1-D coordination-based Rh-Rh molecular wires on gold surfaces.
Reaction of dimeric [Rh(II)(2)(phen)(2)(μ-OAc)(2)(MeCN)(2)](BF(4))(2) (phen =1,10-phenanthroline) with pyrazine (pz) in a 1:2 ratio leads to the new 1-D metal-metal-bonded coordination oligomer {[Rh(II)(2)(phen)(2)(μ-OAc)(2)(pz)](BF(4))(2)}(n) (Rh-Rhpz)(n) (1), where each Rh atom of the dimeric unit (Rh-Rh) is coordinated in the equatorial plane to a nitrogen atom of a rigid and linear bifunctionalized organic linker (pz). Single X-ray diffraction analysis reveals the 1-D straight oligomeric chain structure (molecular wire, MW) consists of alternating (Rh-Rh) units and pz linking ligands with free BF(4)(-) as counteranions, and each metal center has a slightly distorted octahedral arrangement. The presence of accessible labile MeCN groups on both ends of these MWs ("free ends") enables  functionalization of a 4-mercaptopyridine-gold coordinating platform (Au/MP) to form in one step a layer of coordination oligomer (Au/MP(Rh-Rhpz)(n); n ≈ 50). Furthermore (Rh-Rhpz)(n) (n = 1-6) MWs were grafted to Au/MP surfaces by a conventional step-by-step assembly construction involving coordination reactions between the Rh dimer ([Rh(2)(phen)(2)(μ-OAc)(2)(MeCN)(2)](BF(4))(2) (2)) and pz. A detailed physicochemical study (UV-vis, RAIR, QCM-D, ellipsometry, contact angle measurements, as well as impedance spectroscopy and cyclic voltammetry) has been made during both assembly methods to characterize the resulting surface-anchored coordination molecular wire (CMW) layers (Au/MP(Rh-Rhpz)(n)). The results indicate that the immobilized molecular assemblies (MAs) were successfully fabricated using both methods of assembly. The efficiency of the two methods is discussed.
Département de Chimie Moléculaire UMR 5250, Laboratoire de Chimie Inorganique Redox, Université Joseph Fourier-Grenoble1/CNRS, Institut de Chimie Moléculaire de Grenoble FR-CNRS-2607, BP53, Grenoble, F-38041, France.
Koodlur Sannegowda
KS
Lokesh
Sylvie
S
Chardon-Noblat
Frédéric
F
Lafolet
Youssouf
Y
Traoré
Chantal
C
Gondran
Philippe
P
Guionneau
Liliane
L
Guérente
Pierre
P
Labbé
Alain
A
Deronzier
Jean-François
JF
Létard