Electrochemical behavior and dioxygen reactivity of tripodal dinuclear copper complexes linked by unsaturated rigid spacers.

New dinucleating ligands based on two tripodal tris(2-pyridylmethyl)amine (TMPA) units linked by a series of delocalized π-electrons spacers have been synthesized. Their di-Cu(II) complexes have been prepared and structurally characterized. As compared to the corresponding monotopic complexes, these dinuclear Cu(II) complexes reveal spectroscopic and voltammetric features ascribable to weakly perturbed electronic interactions. In the case of the anthracenyl spacer, observation both in the solid and in solution suggests that the existence of intramolecular π-π stacking interactions influences the geometry of the complex and hence its electronic properties. The bis-Cu(I) complexes were prepared electrochemically. In the specific case of the complex bearing a mono-alkyne spacer, addition of dioxygen in acetonitrile leads to the slow formation of a trans-µ-1,2 peroxo Cu(2) complex which shows good stability at 268 K (t(1/2) = 240 s). Analysis of the kinetics of the peroxo formation by UV-vis spectroscopy suggests that the increased activation barrier for intramolecular binding of dioxygen is due to the rigidity of the spacer.

A generic platform for the addressable functionalisation of electrode surfaces through self-induced "electroclick".

A novel and general strategy for the immobilisation of functional objects onto electrodes is described. The concept is based on the addition of two pendant ethynyl groups onto a bis(pyridyl)amine derivative, which acts as a molecular platform. This platform is pre-functionalised with an N(3)-tagged object of interest by Huisgen cycloaddition to one of the ethynyl groups in biphasic conditions. Hence, when complexed by Cu(II) , this molecular-object holder can be immobilised, by a "self-induced electroclick", through the second ethynyl group onto N(3)-alkanethiol self-assembled monolayers on a gold electrode. Two different functional groups, a redox innocent ((CH(2))(3)-Ph) and an electrochemical probe (ferrocene), were immobilised by following this strategy. The in situ electrochemical grafting showed, for both systems, that the kinetics of immobilisation is fast. The voltammetric characterisation of the surface-tagged functionalised copper complexes indicated that a good surface coverage was achieved and that a moderately fast electron-transfer reaction occurs. Remarkably, in the case of the redox-active ferrocenyl-immobilised system, the electrochemical response highlighted the involvement of the copper ion of the platform in the kinetics of the electron transfer to the ferrocene moiety. This platform is a promising candidate for applications in surface addressing in areas as diverse as biology and materials.

Self-induced "electroclick" immobilization of a copper complex onto self-assembled monolayers on a gold electrode.

We report the self-induced "electroclick" immobilization of the [Cu(II)(6-ethynyl-TMPA)(H(2)O)](2+) complex, by its simple electro-reduction, onto a mixed azidoundodecane-/decane-thiol modified gold electrode. The redox response of the grafted [Cu(II/I)(TMPA)] at the modified electrode is fully reversible indicating no Cu coordination change and a fast electron transfer.

Electrochemical, spectroscopic, and structural evidence for the mild hydrolysis of tetracyanoethylene, TCNE, to form the 2,3,3-tricyanoacrylamidate ligand: isolation of an unexpected quadruply-bonded polymeric material [Mo2(O2CCMe3)3((NC)2CC(CN)CONH)]infinity.

Under strictly anhydrous conditions, no reaction occurs between Mo(2)(O(2)CCMe(3))(4) and tetracyanoethylene, TCNE, at room temperature, but after addition of 1 equiv of water, a reaction proceeds to form [Mo(2)(O(2)CCMe(3))(3)((NC)(2)CC(CN)CONH)], 1. The compound contains a quadruple-bonded Mo(2) unit and the 2,3,3-tricyanoacrylamidate anion as a ligand (TC3A), a very unusual hydrolyzed form of TCNE. Two different solid-state structures were obtained after crystallization of 1. Crystals obtained from CH(2)Cl(2) consist of a two-dimensional network, and crystals grown from a C(6)H(6) solution form a 1-D chain motif. In both cases, the TC3A ligand acts as a polydentate ligand involving a bidentate OCN bridging unit and two CN groups. The electrochemical and spectroscopic (IR, UV/vis/near-IR, NMR, EPR) properties of 1 support the formulation in solution as a discrete 1:1 complex of the TC3A donor ligand and a Mo(2) unit with no charge transfer. The coordinated TC3A ligand exhibits redox properties similar to those of free TCNE.

From the Single- to the Triple-Decker Sandwich. Effect of Stacking on the Redox and UV-Visible Spectroscopic Properties of Lutetium(III) 1,2-Naphthalocyaninate Complexes.

(1,2-Naphthalocyaninato)lutetium(III), bis(1,2-naphthalocyaninato)lutetium(III), and tris(1,2-naphthalocyaninato)dilutetium(III) have been synthesized in good yields. These complexes were characterized by UV-visible, (1)H NMR, and mass spectroscopies and by electrochemical techniques. Bis(1,2-naphthalocyaninato)lutetium(III) is compared to bis(2,3-naphthalocyaninato)lutetium(III): the good correspondance between the experimental data and theoretical results obtained by others is emphasized in this work. Stacking one to three macrocyclic rings is possible in the series of the 1,2-naphthalocyanine sandwich-like complexes with lutetium(III); as shown by UV-visible spectroelectrochemistry and voltammetry, this influences greatly the pi-conjugated systems, modifying spectacularly their spectroscopic and redox properties.