Nicolas Le Poul

Université de Bretagne Occidentale | UBO

Whereas molybdenum dinitrogen complexes have played a major role as catalytic model systems of nitrogenase, corresponding tungsten complexes have in most cases found to be catalytically inactive. Herein we present a modified pentadentate tetrapodal (pentaPod) phosphine ligand in which two dimethylphosphine groups of the original PMe2PPh2 ligand hav...

This review summarizes the latest discoveries in the field of C–H activation by copper monoxygenases and more particularly by their bioinspired systems. This work first describes the recent background on copper-containing enzymes along with additional interpretations about the nature of the active copper–oxygen intermediates. It then focuses on rel...

Copper–oxygen adducts are known for being key active species for the oxidation of C–H bonds in copper enzymes and their synthetic models. In this work, the synthesis and spectroscopic characterizations of such intermediates using dinucleating ligands based on a 1,8 naphthyridine spacer with oxazolines or mixed pyridine-oxazoline coordination moieti...

A series of phosphorescent platinum(II) complexes containing various phenyldiazine-type bidentate N^C ligands has been successfully synthesized and characterized. Structural modifications have been made to bidentate cyclometalating ligands regarding the nature of diazine ring (pyrimidine, pyrazine and quinazoline), the substituent groups at the C4...

Copper (Cu) sensing in the nanomolar range is an important challenge for marine water monitoring, especially with eco-friendly materials and reagents. For this purpose, electrochemical Cu(II) sensors appear as fully suitable because of their relatively high sensitivity, selectivity and adaptability for in situ measurements. So far, one of the usual...

We present here a novel strategy based on the covalent grafting of a C -functionalized Ni-cyclam complex onto glassy carbon to achieve heterogeneous electrocatalytic CO 2 reduction in neutral water at low...

The tungsten dinitrogen complex [W(N2)(PMe2PPPh2)] (2) (PMe2PPPh2 = [2-({bis[3-(diphenylphosphino)propyl]-phosphino}methyl)-2-methylpropane-1,3-diyl]bis(dimethylphosphine)) is synthesized and characterized by X-ray diffraction as well as IR and NMR spectroscopies, showing strong analogies to its molybdenum analogue [Mo(N2)(PMe2PPPh2)] (1). Whereas...

In this article, we report on a series of cyclometalated chloro- and alkynyl-platinum(II) complexes bearing various tridentate N^C^N-cyclometalated ligands derived from 1,3- bis(pyrimidin-2-yl)benzene. The X-ray crystal structures of two alkynyl-platinum(II) complexes were determined and other structures were DFT-calculated. Electrochemical and DFT...

A series of luminescent chloro- and alkynyl-platinum (II) complexes containing various tridentate cyclometalated ligands derived from phenyl-pyridin-2-ylpyrimidine and alkynyl ligands has been successfully synthesized and characterized. Their electrochemical, electronic absorption and luminescence properties have been experimentally investigated an...

This review is focused on the current state-of-the art of low-temperature electrochemistry and spectroelectrochemistry applied for coordination and organometallic compounds. From the first tentative steps in the 1960s to the present sophisticated spectroelectrochemical systems, low-temperature studies of redox reactions and coupled chemical process...

The activation of carbon dioxide by three different Mo‐diimine complexes [Mo(CO) 4 (L)] (L = bipyridine (bpy), 1,10‐phenantroline (phen) or pyridylindoziline (py‐indz)) has been investigated by electrochemistry and spectroelectrochemistry. Under inert atmosphere, monoreduction of the complexes is ligand‐centred and leads to tetracarbonyl [Mo(CO) 4...

A series of four D-(π-Pt-π-A)2 new V-shaped binuclear platinum(ii) complexes bearing a diphenylpyranylidene ligand as a pro-aromatic donor group (D) and various electron-attracting groups (A) separated by platinum bis-acetylide fragments have been synthesized, characterized and studied for their electrochemical, photophysical and second-order nonli...

This paper aims at providing theoretical basis on electrochemical processes performed at low temperature (T) according to three different aspects. First, the effect of T-decrease is treated in terms of thermodynamics, mass-transfer, and kinetics of electron transfer (ET) heterogeneous reactions. In particular, predictions of ET kinetics at low temp...

The deliberate surface modification of nanocatalysts with organic ligands has recently emerged as a promising strategy to boost their efficiency, durability, and/or selectivity in key electrocatalytic processes. The interface between the metallic interface and the immobilized ligands promotes high electrocatalytic activity. Herein, the oxygen reduc...

Mono- and di-anchoring γ-pyranylidene-based organic dyes featuring D–π–A and D–(π–A)2 architectures have been engineered as sensitizers for applications in Dye-Sensitized Solar Cells (DSSCs). Their photophysical, electrochemical and photovoltaic properties were further investigated. TD-DFT calculations were performed to rationalize the trends obser...

A series of copper/nitrosoarene complexes was created that mimics several steps in biomimetic O2 activation by copper(I). The reaction of the copper(I) complex of N,N,N',N'-tetramethypropylenediamine with a series of para-substituted nitrosobenzene derivatives leads to adducts in which the nitrosoarene (ArNO) is reduced by zero, one, or two electro...

The electrochemically generated Cu II Cu III mixed-valent species promotes activation of strong aliphatic C—H bond (i.e. toluene) at room temperature. The mechanistic pathway turns from stoichiometric to catalytic upon addition of base,...

Three different mononuclear copper(II) complexes 1–3 bearing ditopic macrocyclic ligands (L¹ or L²) have been prepared. Both ligands include two coordinating cores, namely tris(methylpyridyl)amine (TPA) and pyridine-dicarboxamide (PydCA). Complexes 1–3 have been characterized in solid state, and in solution by UV–Vis and EPR spectroscopies, as well...

We report herein the synthesis of nine new molecularly engineered metal-free organic pyranylidene-based dyes as efficient photosensitizers for Dye-Sensitized Solar Cells (DSSCs). Their photophysical, electrochemical, and photovoltaic properties were investigated, and their excited states have been modelled using Time-Dependent Density Functional Th...

The electrochemically-induced C–C bond making/breaking for six differently R-substituted phenylmethylenepyrans has been investigated by voltammetry in organic media. All compounds display an irreversible oxidation peak whose potential is fully dependent on the electrophilic property of the substituent R. The electrochemical oxidation yields bis-pyr...

We present here the synthesis of two new bifunctionalized azachelators, no2th-EtBzNCS and Hno2th1tha, as bioconjugable analogues of two previously described di- and trimethylthiazolyl 1,4,7-triazacyclononane (tacn) ligands, no2th and no3th, for potential uses in copper-64 ( ⁶⁴ Cu) positron emission tomography imaging. The first one bears an isothio...

Two novel tripodal ligands L1 and L2 based on a tris(methylpyridyl)amine (TPA) motif have been prepared and reacted with two different iron(II) salts. The ligand L1 contains a bis(amino-phenyl)-TPA group whereas the macrocyclic ligand L2 displays two different coordinating cores, namely TPA and pyridine-dicarboxamide. The resulting mononuclear comp...

A (μ-hydroxido, μ-phenoxido)CuIICuII complex 1 has been synthesized using an unsymmetrical ligand bearing an N, N-bis(2-pyridyl)methylamine (BPA) moiety coordinating one copper and a dianionic bis-amide moiety coordinating the other copper(II) ion. Electrochemical mono-oxidation of the complex in DMF occurs reversibly at 213 K at E1/2 = 0.12 V vs F...

Functionality of enzymes is strongly related to water dynamic processes. The control of the redox potential for metallo-enzymes is intimately linked to the mediation of water molecules in the first...

This paper presents the syntheses and photophysical and the electrochemical characterizations of four new mono- and diplatinum polyynediyl complex chromophores end-capped with diphenylpyranylidene and pentafluorophenyl moieties. The nonlinear optical properties (NLO) of these compounds are investigated using the electric-field-induced second harmon...

The redox properties of the μ-η2:η2 peroxo complex [Cu2(H6M4h)(O2)]2+ were elucidated. This study constitutes the first full electrochemical and spectroelectrochemical characterization of a side-on peroxo Cu2:O2 bioinorganic model complex. The...

Water oxidation by copper-based complexes to form dioxygen has attracted attention in recent years, with the aim of developing efficient and cheap catalysts for chemical energy storage. In addition, high-valent metal–oxo species produced by the oxidation of metal complexes in the presence of water can be used to achieve substrate oxygenation with t...

The present work describes the one-pot synthesis, electrochemical, photophysical and second order nonlinear optical (NLO) properties of a series of dipolar π-delocalized Ru(II) dialkynyl complexes. The eight new asymmetrical D–π-Ru–π-A push–pull chromophores incorporate pyranylidene ligands as pro-aromatic donor groups (D) and formaldehyde, indane-...

A water-soluble calix[6]azacryptand coordinates copper(II) over a wide range of pH. Due to second coordination sphere effects and the hydrophobic effect ascribed to the calixarene cavity, this funnel complex selectively binds neutral molecules (alcohols, nitriles, amines) versus anions in water near physiological pH. More specifically, it behaves a...

Direct experimental determination of redox properties of superoxo (O2*-) and peroxo (O22-) embedded in dicopper complexes bearing an unsymmetrical binucleating ligand was achieved using cryo-electrochemistry and cryo-spectroelectrochemistry in dichloromethane. Cyclic voltammetry for dicopper(I) (1+) oxidation to a Cu(I)Cu(II) mixed-valent species (...

Electrochromic organic systems that can undergo substantial variation of their optical properties upon electron stimulus are of high interest for the development of functional materials. In particular, devices based on radical dimerization are appropriate because of the effectiveness and speed of the carbon-carbon bond making/breaking. Phenylmethyl...

In the present paper, we report on the influence of methanol/methoxide on the structure and the mono-electronic oxidation process of two different dicopper(II,II) complexes: a binuclear μ-alkoxo μ-acetato dicopper(II,II) complex obtained with a tetraamide-containing ligand (1) or a new unsymmetric μ-phenoxo, μ-hydroxo dicopper(II,II) complex based...

A new "two-story" calix[6]arene-based ligand was synthesized, and its coordination chemistry was explored. It presents a tren cap connected to the calixarene small rim through three amido spacers. X-ray diffraction studies of its metal complexes revealed a six-coordinate Zn(II) complex with all of the carbonyl groups of the amido arms bound and a f...

Spectroelectrochemical and computational studies of phenoxo-bridged dinuclear complexes show that unsymmetrical design of the ligand induces the formation of a transient mixed-valence (II,III) species upon oxidation.

In this article, we describe the synthesis, redox characteristics, linear and nonlinear optical (NLO) properties of seven new unsymmetrical push-pull diacetylide platinum-based complexes. These D-π-Pt-π-A complexes incorporate pyranylidene ligands as pro-aromatic donor groups (D), diazine rings as electron-withdrawing groups (A), and various aromat...

In this study, we report on the synthesis of a dinuclear copper(II) complex supported by 1,3-diamino-2-propanol based tetra-amide ligand. Structural properties in the solid state and in solution, using X-Ray diffraction analysis and NMR spectroscopy respectively, have evidenced a highly flexible complex that can display several conformations leadin...

The immobilization of a copper calix[6]azacryptand funnel complex on gold modified electrodes is reported. Two different methodologies are described. One is based on alkyne-terminated thiol self-assembled monolayers. The other relies on the electrografting of a calix[4]arene platform bearing diazonium functionalities at its large rim and carboxylic...

Bis(μ-hydroxo)dicopper(II,II) bearing a naphthyridine-based ligand has been synthesized and characterized in the solid state and solution. Cyclic voltammetry at room temperature displays a reversible redox system that corresponds to the monoelectronic oxidation of the complex. Spectroscopic and time-resolved spectroelectrochemical data coupled to t...

A tacn based ligand bearing two methylthiazolyl arms (no2th) was synthesized with the aim to find ligands forming very stable and inert complexes with Cu(II) and Cu(I) in aqueous medium for radiopharmaceutical applications. The no2th ligand was efficiently prepared following the orthoamide intermediate synthesis. The complexes with Cu2+ and Zn2+ we...

Aiming to develop new copper chelates for application in nuclear medicine we report two new chelators, te1th and te2th, based on a cyclam backbone mono-N- or di-N1,N8-functionalized by methylthiazolyl arms. The acid-base properties of both ligands were investigated as well as their coordination chemistry, especially with Cu(2+), when possible in aq...

Supramolecular bioinorganic chemistry is a natural evolution in biomimetic metallic systems since it constitutes a further degree of complexity in modeling. The traditional approach consisting of mimicking the first coordination sphere of metal sites proved to be very efficient, because valuable data are extracted from these examples to gain insigh...

The controlled motion of ions, molecules, or supramolecular entities has inspired scientists for more than 25 years, and the concept remains of great interest for the development of moveable nanoscale objects for applications in electronics, medicine, and materials chemistry. Artificial molecular machines that involve electron exchange processes in...

Modeling the mononuclear site of copper enzymes is important for a better understanding of the factors controlling the reactivity of the metal center. A major difficulty stems from the difficult control of the nuclearity while maintaining free sites open to coordination of exogenous ligands. A supramolecular approach consists in associating a hydro...

In this joint experimental-theoretical work, we present the synthesis and optical and electrochemical characterization of five new bis-acetylide platinum complex dyes end capped with diphenylpyranylidene moieties, as well as their performances in dye-sensitized solar cells (DSCs). Theoretical calculations relying on Time-Dependent Density Functiona...

Localized "electro-click" was achieved on azido-terminated self-assembled monolayers using Scanning Electrochemical Microscopy (SECM) in feedback mode in which the substrate is not electrically connected (unbiased conditions). The method allows both the local immobilization of diverse functional moieties and the monitoring of each modification step...

The coordination properties of the biomimetic complex [Cu(TMPA)(H2O)](CF3SO3)2 (TMPA = tris(2-pyridylmethyl)amine) have been investigated by electrochemistry combined with UV-Vis and EPR spectroscopy in different non-coordinating media including imidazolium-based room-temperature ionic liquids, for different water contents. The solid-state X-ray di...

The reactivity of the mononuclear [Cu(TMPA)(L)]n+ complex (TMPA: tris(2-methylpyridine)amine, L: CH3-CN, H2O) towards two different bridging species (tetracyanoethylene, 4,40-bipyridine) was investigated. The dinuclear complex [(l-4,40-bipy){CuII(TMPA)}2](CF3SO3)4 (1) was synthesised and analysed by Xray diffraction (XRD). Magnetic studies revealed...

Two new Cu complexes bearing a 6-ethynyl bis-(methyl-pyridyl) amine (6eBMPA) moiety, as an electroclickable function linked to a ferrocenyl-based triazolyl arm (ligands 3 and 4) have been synthetized and characterized by UV–Visible, EPR spectroscopies and cyclic voltammetry in acetonitrile. Two different spacer groups between the terminal ferrocene...

The coordination of CuI to a poly(imidazole) core is of the most importance in biology as it is present in most enzymes as well as in peptides involved in pathological processes. Here, we report a detailed study of the binding of CuI to a tris(imidazole) core constructed on a resorcinarene scaffold. NMR and IR spectroscopy as well as cyclic voltamm...

A biomimetic copper complex has been attached as SAMs onto an azidoundecanethiol-modified gold electrode by the "self-induced electroclick" procedure. The immobilized complex electrocatalyzes efficiently the reduction of nitrite ions in an acidic medium. The in-situ control of the surface coverage during the grafting process by the electroclick app...

The conformation of copper "funnel" complexes that contains a coordinating appended arm can be electrochemically switched between endo, which corresponds to the self-coordination of the arm through the cavity, and exo positions. This process, which is reminiscent of a cup-and-ball device, is activated by an exogenous ligand for complexes that conta...

Electro or chemical oxidation of ferrocenylmethylenepyran gave an ethanediferrocenylbispyrylium salt through the dimerization of a ferrocenylpyran radical-cation (C–C bond making). Electro or chemical reduction gave back the ferrocenylmethylenepyran (C–C bond breaking). This electrochemical reverse system constitutes an example of C–C bond making–b...

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 a...

Asymmetrical N-tripodal ligands have been synthesized in three steps. Diversity has been introduced at the first step of the synthesis by adding pyrazine, pyridine, benzyl and thiophene rings. The corresponding CuII complexes have been prepared by reaction with CuCl2 and characterized by Electron Paramagnetic Resonance (EPR), UV-Vis spectroscopies...

The derivatization of the large rim of a TMPA-capped calix[6]arene (TMPA = tris(2-pyridylmethyl)amine) with three trimethylammonium groups enables the water-solubilization of two air-stable Cu(I)/Cu(II) complexes. These two complexes present a vacant coordination site shielded from the aqueous environment by the calixarene core. The spectroscopic a...

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...

Huisgen dipolar cycloaddition leads straightforwardly to new funnel complexes based on the calix[6]arene macrocycle bearing three functionalized triazoles as coordinating units at the small rim. Coordination to Zn(II) and Cu(I) cations was studied using (1)H NMR and IR spectroscopies and cyclic voltammetry. The nature of the substituents on the tri...

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...

A ditopic ligand based on a calix[6]arene with three imidazoles (Im) appended at the small rim and three triazoles (Tria) at the large one is able to form selectively two stable heterodinuclear complexes with Zn(II)(Im)/Cu(I)(Tria) and Cu(II)(Im)/Zn(II)(Tria). In the Cu(I) case, the zinc cation is preferentially coordinated at the Im site while the...

Ferrocenyl and pyridyl methylenepyrans were obtained from a Wittig reaction between a pyran phosphorane and ferrocenyl or pyridyl-aldehydes. The nucleophilic nature of the exocyclic C–C bond allowed the formylation of these compounds by a Vilsmeier type reaction. All the new products were characterized by IR spectroscopy, 1H and 13C NMR spectroscop...

The control of metal-ligand exchange in a confined environment is of primary importance for understanding thermodynamics and kinetics of the electron transfer process governing the reactivity of enzymes. This study reveals an unprecedented change of the Cu(II)/Cu(I) binding and redox properties through a subtle control of the access to the labile s...

Electrochemical or chemical dimerization of electron-rich ferrocenylmethylenepyran 1 gave the first dimetallocenylbispyrylium salt 2 known today, through a reverse process that implies reductive C−C bond breaking. Deprotonation of the bispyrylium salt 2 afforded extended electron-rich diferrocenyl bispyran 3, which was subsequently reversibly oxidi...

The electrochemical behavior of diversely substituted Cu-N3-calix[6]arene, enzyme-like, "funnel" complexes is analyzed. The Cu(II)/Cu(I) redox process is regulated by the supramolecular organization of the Cu coordination. The presence of a "shoetree" alkyl nitrile guest molecule inside the host cavity is a prerequisite for a dynamic redox behavior...

Extended electron rich bis-chalcogenapyrans and bis-benzochalcogenapyrans have been synthesized by Pd0 catalyzed dimerization of α- and γ-methylene chalcogenapyran and benzochalcogenapyran Fischer type carbene complexes. Voltammetric studies performed on these molecules show a single two-electron wave around 0V versus SCE, which is ascribed to the...

Low-temperature heterogeneous electron-transfer kinetics of decamethylferrocene obtained from a.c. impedance analysis are reported. The experiments have been performed for 120 K < T < 200 K with a gold working electrode in two different electrolyte solution mixtures containing equal amounts of decamethylferrocene and decamethylferricinium tetrafluo...

The electrochemical behavior of the tris(pyridine) calix[6]arene Cu adducts is unique as compared to that of most classical Cu complexes in a strain-free environment. The presence of MeCN buried inside the cavity is a prerequisite for a quasi-reversible behavior in a dynamic mode. The CV behavior assisted by simulation outlines that the coordinatio...

The cyclic voltammetry of ferrocene (CpFeCp) adsorbed as a monolayer of CpFeCpCO2(CH2)8SH, self-assembled onto the Hg-based high-temperature superconductor Hg0.8Re0.2Ba2Ca2Cu3O10 (Tc = 134 K), via an ultrathin (3.1 nm) Ag film, has been performed in liquid electrolyte (16:7:1 EtCl/THF/2-MeTHF; 0.2 M LiBF4) at a range of temperatures spanning the su...

The first kinetic measurements for electron transfer (ferrocene/ferricinium reaction) at the interface between an HTSC (Tl,Pb1223) and a redox polymer (ferrocene-tagged poly-pyrrole) show that superconductivity affects electron transfer rate, which thus offers a novel probe of the superconducting state.

The first kinetic measurements for electron transfer (ferrocene/ferricinium reaction) at the interface between an HTSC (Tl,Pb1223) and a redox polymer (ferrocene-tagged polypyrrole) show that superconductivity affects electron transfer rate, which thus offers a novel probe of the superconducting state.

We have demonstrated the feasibility of developing stable Li+ potentiometric sensors, using a composite plastic technology as electrode support. Both triphylite LiFePO 4 - and FePO 4 -based sensors display good Li+ sensing properties (reversibility, stability, linearity in the serum Li+ concentration range). Besides, the reversible insertion of var...

The condensation reaction between γ-unsubstituted pyrylium salts and carbanions of Fischer-type carbene complexes allowed the synthesis of new γ-methylenepyran carbene complexes. NMR data, single crystal X-ray analysis, and DFT calculations suggest that these complexes have a partial pyrylium character due to the π electron-accepting ability of the...

Self dimerisation of methylenepyran carbene complexes affords bis-pyrans containing electron rich polyene linkage. The cyclic voltammograms of these new donors show one two-electron oxidation wave at low potential.