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An efficient nanocomposite anode material for the oxygen evolution reaction (OER) based on nickel oxide nanoparticles entrapped in a polypyrrole matrix has been readily synthesized by an all-electrochemical procedure. Examples of anodes for the OER utilizing metallic nanoparticles dispersed in an organic polymer film are still scarce but very promising for water splitting applications. Herein, nickel metal (Ni0) nanoparticles were first electrodeposited into a cationic poly(pyrrole-ammonium) film (poly1) electropolymerized onto carbon or ITO electrodes by reduction of an anionic nickel oxalate complex in aqueous borate buffer at pH 6. The Ni0 nanoparticles were then electro-oxidized into nickel oxide (NiOx) in aqueous borate buffer at pH 9.2. The physical, chemical and electrocatalytic properties of the nanostructured poly1–NiOx material were evaluated by inductively coupled plasma mass spectroscopy (ICP-MS), atomic force microscopy (AFM) and transmission electron microscopy (TEM) coupled to various electrochemical techniques, and the results were compared with those of NiOx directly deposited on a naked electrode (without polymer) by the same electrochemical procedure. Such characterization clearly evidences the beneficial role of the poly1 matrix to generate smaller and non-agglomerated NiOx particles. Owing to the small size of NiOx nanoparticles (ca. 21 nm) and the great nanostructuration of the poly1–NiOx composite film deposited on the carbon (C) electrode surface, this material displays a very high electrocatalytic OER performance in a nearly neutral solution (pH 9.2) and even in alkaline solution (pH 14) with strong mass activities and turnover frequencies (TOFs) (1.12 A mg−1 and 0.17 s−1, respectively, at an overpotential of 0.61 V at pH 9.2, and of 1.28 A mg−1 and 0.19 s−1, respectively, at an overpotential of 0.35 V at pH 14). This performance places the C/poly1–NiOx electrode among the most active anodes based on nickel oxide reported in the literature and undoped with iron ions for the OER. In addition, when the poly1–NiOx film is deposited on a porous ITO electrode, its physisorption on the electrode surface is significantly enhanced, as shown by long-term electrocatalysis at 1.2 V vs. Ag/AgCl. Indeed, its catalytic current remains constant after several days of electrocatalysis, demonstrating the great stability of the poly1–NiOx nanocomposite; the polymer matrix maintains the integrity of the NiOx nanoparticles and precludes their corrosion. This material is thus very promising for the implementation of efficient and highly stable anodes for water oxidation.

Nanocomposite anode materials for water oxidation have been readily synthesized by electrodeposition of iridium oxide nanoparticles into poly(pyrrole-alkylammonium) films, previously deposited onto carbon electrodes by oxidative electropolymerization of a pyrrole-alkylammonium monomer. The nanocomposite films were characterized by electrochemistry, transmission electron microscopy, and atomic force microscopy. They showed an efficient electrocatalytic activity toward the oxygen evolution reaction. Data from Tafel plots have demonstrated that the catalytic activity of the iridium oxide nanoparticles is maintained following their inclusion in the polymer matrix. Bulk electrolysis of water at carbon foam modified electrodes have shown that the iridium oxide-polymer composite presents a higher catalytic activity and a better operational stability than regular oxide films.

Indexación: Web of Science; Scopus; Scielo. Arsenic occurs in a variety of forms and oxidation states and is a very toxic element. The main inorganic arsenic species present in natural waters are arsenate (oxidation state V) and arsenite ions (oxidation state III). Arsenite is more toxic and mobile than arsenate. Therefore, it is important the development of new materials for analysis and control of these toxic species. This research proves that polymer-metal composite electrode materials synthesized by incorporation of Pt-0 and Pd-0 nanoparticles into a poly(pyrrole-ferrocenyl alkylammonium) matrix present electrocatalytic properties towards the oxidation of arsenite to arsenate. The polymer films displayed a stable electrochemical response in aqueous solution. However, when the polymer film modified electrode were transferred to aqueous solution in presence of arsenite anions, the CV curves for polymer films were deeply modified by the decrease in the electroactivity of the film. It can be concluded that the cationic polymer films present a strong affinity toward arsenite anions. The composite films containing Pt-0 or Pd-0 showed catalytic activity towards oxidation of As(III) to As(V) due to the presence of metal catalyst particles into the polymer films. http://ref.scielo.org/dgdvxf

Summary: The complexing properties of poly (3-(pyrrol-1-yl)propylmalonic acid) (poly1) and poly(N,N′-ethylenebis[N-[(3-(pyrrole-1-yl)propyl) carbamoyl) methyl]-glycine (poly2) coated electrodes (C|poly1 and C|poly2) towards Cu(II), Pb(II), Hg(II) and Cd(II) cations using the open circuit chemical preconcentration-anodic stripping technique were studied. Sorption process of metal cations onto complexing surfaces was readily investigated through the combination of a chemical pre-concentration-anodic stripping technique with a Langmuir isotherm model. The modified electrodes were used for the voltammetric determination of Cu(II), Pb(II), Hg(II) and Cd(II) ions, giving low detection limits for Cu(II) (5 × 10−9 mol L−1) and Pb(II) (5 × 10−10 mol L−1). The ability of the modified electrodes to analyze Cu(II) ions in natural sample has been demonstrated by the analysis of a tap water sample. The results of the preconcentration process under competitive conditions clearly shows that the selectivity of complexing molecular electrode materials can be subtly tuned upon playing on the accumulation time, polymer thickness and/or memory effect of the binding polymers, opening up new avenues towards evolutive and efficient smart sensing materials.

Summary: Soluble coordination polymers and gels built from a polytopic ligand containing two terpyridine units linked by a azamacrocyclic group are presented. This system originally incorporates two different types of metal complexes in the same polymer chain which induces remarkable electrochromic properties and a rare redox triggered reversible sol-gel transition.

This review article focuses on the syntheses and potential applications of ferrocene-appended porphyrin architectures. Several strategies have been developed to date to associate ferrocenyl fragments and porphyrin rings in the same molecular architecture, depending on the targeted application: (i) connection at a meso position through a direct linkage, a conjugated or saturated spacer or using a non-covalent approach and (ii) connection at a β-pyrrolic position. Examples of ferrocene–porphyrin analogues are also presented.

The effective electrochemical sensing of dihydrogen phosphate and adenosine-5′-triphosphate anions could be achieved in organic electrolytes using self-assembled monolayers of a (ferrocenylmethyl)trialkylammonium cation. The electrochemical response of these modified electrodes was found to be similar to that of the receptor in homogeneous solution. This observation showed that the electrochemical recognition properties of the redox active cationic receptor were fully retained after immobilization on the electrode surface. The recognition abilities of this redox assembly are based on strong ion pairing effects, further reinforced upon oxidation of the ferrocene centres to ferrocenium. The complexation events could be detected and amperometrically quantified through the emergence of new differential pulse voltammetric peaks corresponding to the electroactivity of the (ferrocenylmethyl)alkylammonium-anion complexes.

The complexing ability of thin poly(3-pyrrol-1-ylpropyl)malonic acid films coated onto glassy carbon disc electrode surfaces was evaluated towards Pb(II) and Cu(II) ions, using the chemical preconcentration-anodic stripping method. The affinity of these metal cations for the complexing film modified electrodes and their maximal surface coverage rate could be evaluated from a Langmuir isotherm model coupled to the chemical preconcentration-anodic stripping technique. Isothermal studies conducted between 293 and 308 K allowed to estimate enthalpy and entropy variations associated to the metal sorption, which expectedly proved to fit chemisorption processes. As judged from the estimated binding constants, Pb(II) ions turned out to present a higher affinity for the functionalized surface than the smaller Cu(II) species. The mobilization of a higher number of malonic acid units per metal cation upon complexation of Pb(II), as compared to Cu(II), is however believed to account for the estimated lower Pb(II) surface coverage. The combination of the Langmuir isotherm model to the chemical preconcentration-anodic stripping technique is thus revealed to be an efficient method to characterize the complexing ability of complexing film electrode surface.

Complexing polymer-coated electrodes have been synthesized by oxidative electropolymerization of N , N ′-ethylene bis [ N -[(3-(pyrrole-1-yl)propyl) carbamoyl) methyl]-glycine] ( L ). There were used for the electrochemical detection of Cu(II), Pb(II) and Cd(II) ions by means of the chemical preconcentration-anodic stripping technique. For thick polymeric binding materials and long accumulation times, competitive experiments showed that the poly L film modified electrodes are selective towards Cu(II) ions and particularly insensitive to the presence of Cd(II). In contrast, imprinted polymer-coated electrodes prepared by electropolymerization of the Cd(II) complex of L allowed an efficient complexation and sensing of Cd(II) cations. The selectivity of the molecular electrode materials can thus be subtly modulated upon playing on the accumulation time and on the pre-structuration of the complexing polymers.

Arsenic is one of the most hazardous pollutants, and is present in water, mainly, as As(V) and As(lll), and in its inorganic hydrolysis species. Great efforts have been made to develop effective removal techniques. One alternative is the use of water-soluble polymers containing functional groups to remove these toxic species. This paper presents the synthesis and characterization (FT-IR and 1 H NMR spectroscopy, as well as thermogravimetry TG-DSC) of two cationic water-soluble polymers containing tetra alkylammonium groups, poly[2-(acryloyloxy)ethyl]trimethylammonium chloride, and poly [2-acryloyloxy)ethyl]trimethylammonium methyl sulfate (P(SAETA)). The arsenate retention properties were investigated using the liquid-phase polymer-based retention technique. The polymer structure and the exchangeable anions' nature have been shown to be two important variables in the removal efficiency of arsenate anions from aqueous solutions. Both investigated polymers were found to efficiently remove HASO 2- 4 species from an aqueous media, with pH ranging from 6 to 8. The exchange of methyl sulfate for the chloride anion on P(SAETA) improved arsenate ion retention ability. The modification of ionic strength by Na 2 SO 4 addition induced a significant decrease in the cationic polymer's arsenate retention properties. The polymers' retention properties were not studied using real samples.

The design of more efficient catalytic electrodes remains an important objective for the development of water splitting electrolyzers. In this context a structured composite cathode material has been synthesized by electrodeposition of molybdenum sulfide (MoSx) into a poly(pyrrole-alkylammonium) matrix, previously coated onto carbon electrodes by oxidative electropolymerization of a pyrrole-alkylammonium monomer. The composite material showed an efficient electrocatalytic activity toward proton reduction and the hydrogen evolution reaction (HER). Data from Tafel plots have demonstrated that the electron transfer rate in the composite films is fast, in agreement with the high catalytic activity of this cathode material. Bulk electrolysis of acidic water at carbon foam electrodes modified with the composite have shown that the cathodes display a high catalytic activity and a reasonable operational stability, largely exceeding that of regular amorphous MoSx electrodeposited on naked carbon foam. The enhanced catalytic performances of the composite electrode material were attributed to the structuration of the composite, which led to a homogeneous distribution of the catalyst on the carbon foam network, as shown by SEM characterizations.

The development of photoelectrochemical devices for solar light-driven water splitting and H2 production requires new strategies for the fabrication of materials that combine the necessary photoredox and catalytic properties, to allow the hydrogen evolution reaction (HER) to take place at a low overvoltage under visible light irradiation. We report the first example of a structured composite, synthesized by electrodeposition of MoSx cocatalyst into a photosensitive Ru complex film deposited onto carbon electrodes by electropolymerization of a pyrrole-functionalized Ru(II)(2,2'-bipyridine)3(2+). Composite films show efficient photocatalytic activity for HER. Our study highlights the great simplicity of this versatile electrochemical procedure to synthesize photocathodes.

A new electroactive ligand L built on the Taci (1,3,5-triamino-1,3,5-trideoxy-cis-inositol) platform and bearing three chemically equivalent ferrocene units was prepared and characterized. Electrochemical investigations indicate that electrostatic communication occurs between the three ferrocene groups in L, this electrochemical communication being disrupted in the presence of protons or nucleophilic reagents. Upon addition of metal cations, the electroactivity of L is strongly modified and a remarkable electrochemical signature of the coordination mode adopted by the corresponding complexes is obtained.

The tetra(ferrocene)-cyclam macrocycle 1,4,8,11-tetra(ferrocenylmethyl)-1,4,8,11-tetraazacyclotetradecane (L) and two corresponding CuI and CuII complexes have been prepared and characterized from spectroscopic and electrochemical studies (cyclic voltammetry and rotating disk electrode experiments). Both complexes exist under two energetically distinct geometries which differ mainly from the relative positionning of the ferrocenylmethyl groups above or below the macrocyclic plane and it is shown that a reversible change from one geometry to the other can be electrochemically induced following a copper-centered electron transfer. The equilibrium constants, mechanisms and kinetic parameters of these rearrangements have been evaluated using electrochemical simulation.

A range of ferrocenyl derivatives, L1–L3 and L1Cu, has been prepared and their electrochemical recognition properties in organic solvents have been studied. These compounds are built on the same cyclam framework (ferrocenyl trans di-substitued cyclam), but they differ by the nature of their anions binding sites. While L1 and its corresponding N-methylated L2 derivative can interact with anionic species via H-bonding, strong electrostatic and hard acid–hard base interactions with anionic species are mainly involved in the ammonium derivative L3 and the copper(II) complex L1Cu, respectively. Significant CV perturbations in the characteristic potential of the Fc/Fc+ subunit in the presence of anions were found with L1 and L3. Selectivity of the electrochemical process is likely to be based on the formation of multiple H-bonds between the secondary amines of L1 and the phosphate anions (both H-donor and acceptor) when the topology of the ammonium derivatives, L3, governs mainly the anion complexation. Clear cyclic voltammetric features, such as a well-defined two-wave behavior allowing an accurate amperometric titration, require that the redox receptor contain an appropriate binding site and the ferrocene group in close proximity. Lewis acid–base interactions were shown to influence more deeply the electroactivity of Lewis acid center, namely the copper center in L1Cu, than that of the ferrocenyl redox probe that is not directly connected to the associated anion. However, the precipitation of the host structure (e.g., L3 or L1Cu) in the presence of oxo-anions shows that a compromise has to be found between the establishment of strong interactions and the formation of soluble ion-pairs based complexes.

Platinum and gold microelectrode arrays (MEAs), fabricated on silicon substrates with different geometric characteristics, were surface-modified by the potentiostatic electropolymerization of the pyrrole-ferrocene derivative Py(CH2)3NHCOFc, in the case of the platinum MEAs, and chemisorption of the thiol-functionalized ferrocene HS(CH2)6N+(CH3)2Fc, in the case of the gold MEAs. Cyclic voltammetry of these MEAs was typical of thin film behavior. The modified MEAs were investigated for the detection of the dihydrogen phosphate mono-anion in non-aqueous media via differential pulse voltammetry. This was based on electrostatic interaction and/or hydrogen-bonding between the target anion and the amide-ferrocene or ammonium-ferrocene functionalized electrode surfaces. A decrease in the ferrocene (Fc) oxidation peak current with a concomitant increase in the peak current of a new peak at lower potentials was observed when the concentration of the dihydrogen phosphate was increased.

Based on ion-pairing interactions, which are strongly reinforced upon oxidation to their ferrocenium form, (ferrocenylmethyl)trialkylammonium cations are able to electrochemically sense dihydrogenphosphate and ATP anions in organic electrolytes through two-wave voltammetric features, allowing their amperometric titration. The successful transfer of these electrochemical sensing properties from the homogeneous phase to an electrode surface was achieved using functionalized polypyrrole films synthesized by oxidative polymerization of pyrrole-containing (ferrocenylmethyl)trialkylammonium derivatives.

The synthesis and characterization of a novel redox molecular receptor is reported. This chemosensor is structured on a ferrocene fragment whose cyclopentadienyl moieties have been connected to distinct and complementary zinc porphyrin and alkylammonium binding sites, enabling multipoint recognition and detection of anionic species. Cumulative effects of multiple anchoring points on this ammonium–ferrocene–metalloporphyrin chemosensor allowed the unprecedented ferrocene-based voltammetric sensing of halide anions.

The tripodal ligand L built on the tren platform and bearing three chemically equivalent ferrocene units was prepared and characterized. Electrochemical investigations indicate that electrostatic communication occurs between the three ferrocene groups in L, which leads to the observation of two distinct voltammetric waves. The electrochemical communication between the three ferrocene moieties is disrupted in 1:1 (L:M3+) type complexes formed between L and Y3+ or Eu3+ metal cations and their electrochemical response tends towards that of a single three-independent-electrons oxidation wave. Modulation of the electrochemical properties of L in the presence of lanthanide ions might be exploited with a view to their electrochemical sensing in organic and aqueous media. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Copper(I) cations bind to a ferrocene-based ligand bearing two pendant 2,2′-bipyridine groups to form three distinct complexes possessing compositions of 1 ∶ 1, 1 ∶ 2 and 2 ∶ 2 (metal to ligand), respectively. The 2 ∶ 2 complex exists in the form of a double-stranded metallo-helicate but it is unstable in solution with respect to dissociation into the mononuclear species. Stability constants have been determined for each of the complexes using UV-visible spectrophotometric titrations. With this information, together with data derived from competitive complexation studies, electrospray mass spectrometry and electrochemistry, the mechanism by which the metallo-helicate self assembles in solution has been deduced. It is clear that the binuclear complex forms on dimerization of the 1 ∶ 1 complex, for which there is only a small thermodynamic driving force (ΔG0 = −3.5 kJ mol−1).

International audience; By virtue of strong ion-paring interactions that are reinforced following oxidation of ferrocene moieties to ferrocenium form, films synthesized by oxidative polymerization of pyrrole-containing (ferrocenylmethyl)trialkylammonium cations are able to electrochemically sense the dihydrogenphosphate anion in organic electrolytes. Strong and selective affinity of these cationic polymer films towards H2PO4- was evidenced from FT-IR and EQCM experiments. Clear two-wave differential pulse voltammetry features allow the amperometric titration of this anion.

[60]Fullerene, entrapped in a thin polymer film synthesized by oxidative electropolymerization on a layer of an amphiphilic pyrrole derivative mixed with the fullerene and coated onto an electron-conducting substrate, was shown to play the role of a modified photoelectrode. The photocurrents obtained upon irradiation with visible light in the presence of a water soluble electron donor were shown to be very sensitive to the presence of oxygen in the vicinity of the modified electrode, especially at low oxygen concentrations. This behaviour is explained by the competition between the deactivation of the photoexcited states of [60]fullerene by electron transfer from the donor and by energy transfer to molecular oxygen. This basic principle for the design of a new oxygen sensor is discussed.

Oxidative electropolymerization of pyrrole-substituted monoamidoferrocene 1 yields redox polymer films showing marked electrochemical sensing properties towards H 2 PO 4 − and ATP 2− anions in organic electrolytes, as demonstrated by differential pulse voltammetry experiments. This behavior contrasts with the poor sensing properties of monomer 1 .

The coordinative properties of 1,1′-bis(phen)- and bis(terpy)carboxyester-bridged derivatives of ferrocene L1 and L2 (phen refers to 2,9-substituted-1,10-phenanthroline; terpy refers to 4′-substituted-2,2′:6′,2"-terpyridine) towards various transition metal cations have been investigated by a combination of cyclic voltammetry, mass spectrometry and 1H NMR spectroscopy. These novel redox receptors form 1:1 ligand:metal complexes with all the surveyed metal cations (L1: M = CuI, NiII, FeII, HgII; L2: M = NiII, FeII, HgII). Particular attention was paid to the recognition properties of these redox-active ligands, as monitored by the modulation of the potential of the ferrocene/ferricinium (Fc/Fc+) couple upon complexation. Complexation of L1 gives rise to a new emerging Fc/Fc+ redox peak system. In contrast, complexation of L2 does not alter this redox process appreciably. In addition, decomposition of free L2 occurs upon oxidation and causes the growth of a film of an Fe-bis(terpy) complex onto the electrode surface.

By virtue of strong ion-pairing interactions that are reinforced following its oxidation to the ferrocinium form, (ferrocenylmethyl)trimethylammonium cation is able to electrochemically sense dihydrogen phosphate and ATP anions in organic electrolytes; clear two-wave voltammetry features allow their amperometric titration by this very simple derivative of ferrocene.

Poly(pyrrole-malonate) films have been synthesised by oxidative electropolymerisation of the new pyrrole-malonic acid monomer 1. Poly1 films partition strongly the hexaaamine ruthenium cations from aqueous electrolytes, allowing an estimation of the acidity constant values of poly1 from cyclic voltammetry data. The complexation of copper(II) cations in this chelating polymer was evidenced by FT-IR and electrochemical experiments. Electroreduction of the complexed poly1–Cu(II) leads to the precipitation of copper metal in the polymer film.

This paper presents the electrochemical recognition properties of a series of redox-active ionophores containing two distinct complexing cavities: a Schiff base ligand complexed with Ni II ,C u II or Fe III and locked by a flexible polyoxyethylene chain of variable size. Their electrochemical recognition behavior was manifested by the emergence of a new cyclic voltammetry signal or by a progressive redox potential shift upon complexation of their crown ether-like moiety by alkali and alkaline earth metal cations, ammonium cation and protonated dopamine. UV–vis and FAB-MS experiments confirmed the formation of complexes between these receptors and the surveyed cations. Preliminary results have shown that gold electrodes modified by reaction with a receptor containing a thioether group exhibit electrochemical recognition properties similar to those found in homogeneous solution. © 2001 Elsevier Science Ltd. All rights reserved.

Micellar and interfacial behavior of electropolymerizable cationic surfactants containing a pyrrole group, and associated with various counteranions (bromide, nitrate, tetrafluoroborate and tosylat...

Coordination of [Rh I (ED)Cl] 2 and [Rh I (Chel)(ED)] + complexes (ED=1,5-hexadiene; Chel=2,2'-bipyridine and 4,4'-dimethyl-2,2'-bipyridine) in poly(pyrrole-2,2'-bipyridine) films has been investigated by cyclic voltammetry in CH 3 CN electrolyte, and by FT-IR. In any case, the formation of stable poly[Rh(Chel)(ED)] + films contrasts to that observed in the presence of an excess of Chel in acetonitrile, where the reaction of rhodium(I) complexes containing the labile ED ligand leads to [Rh(Chel) 2 ] + species.

Nickel microparticles have been dispersed in conducting anion-exchange polymer films coated on carbon electrodes by oxidative electropolymerization of a pyrrole-alkylammonium monomer. Incorporation of nickel metal in polymeric films was effected by electroreduction of polymer coated electrodes in aqueous electrolytes containing nickel-oxalate complexes. The metal deposition process was examined by voltamperometry. Scanning electron microscopy showed a dispersion of metal particles with sizes ranging from 700 to 1200 nm. The electrocatalytic hydrogenation of a variety of cyclohexanones and cyclohexenones at these electrode materials was performed with good current and product yields.

The adsorption onto glassy carbon electrodes and the electrochemical oxidation in aqueous sodium tosylate or potassium nitrate electrolyte of micelle-forming cationic surfactants derived from pyrrole is described. Electrode coating by nonelectroactive, thin anion-exchanger films was observed, along with the formation of degradation products following reaction between oxidized pyrrole and water. The best film deposition efficiency was obtained with the more hydrophobic pyrrole−surfactant, which is characterized by the lower critical micelle concentration. The formation of conducting polymer films was successfully achieved by electro-oxidation of adsorbed layers of surfactant in electrolytes containing tetrafluoroborate or perchlorate anions, which decrease the solubility of the surfactant in water, thus increasing the hydrophobic character of the monomer layer.

The pyrrole-containing 1,1′-bis(bipyridyl)-substituted derivative of ferrocene L exhibits electrochemical recognition properties towards CuI and NiII in homogeneous solution. PolyL films synthesised by its oxidative electropolymerisation are able to coordinate CuI ions, whereas they do not display coordinating ability for NiII. In contrast, electropolymerisation of L in the presence of CuI or NiII ions readily obtain pre-structured metallated films. These films can be demetallated electrochemically, and then partially remetallated.

Examples of several molecular redox-active receptors containing a ferrocene redox centre and crown ether or bipyridyl moieties as binding site are presented. Their electrochemical recognition properties towards groups I and II (crown ether-based receptors) and Cu+ (2,2′-bipyridine-based receptors) metal cations have been investigated by cyclic voltammetry in homogeneous solution. Among the four ferrocene-crown ether studied, Fcc3 allowed the effective amperometric recognition of Ba2+ and Ca2+ cations owing to the growth of a new redox peak system at the expense of the original Fc/Fc+ wave (two-wave behavior). In addition, comparison of the electrochemical features in the presence of Cu+ cations of ferrocene monosubstituted (Fcb1) and disubstituted (Fcb2) by bipyridyl groups emphasized the beneficial “sandwich” effect on the recognition behavior of ferrocene-based receptors. Polymer films coated onto electrodes surfaces by electropolymerization of pyrrole-substituted Fcc3 and Fcb2 retained the complexation and the amperometric properties, studied by cyclic voltammetry, of the molecular receptors. Furthermore, capacity measurements using electrochemical impedance spectroscopy (EIS) appeared as a good method for detection and titration of metal cations with these polymer-modified electrodes.

A synthetic route to obtain ( R )-(−) ( 1 ), ( S )-(+)-3-(1-pyrrolyl)propyl- N -(3,5-dinitrobenzoyl)-α-phenylglycinate ( 2 ) and derivatives is described. In a first step, pyrrole derivatives were prepared using the Clauson-Kaas method. The esterification, second step, was performed using basic conditions due to sensitivity of the pyrrole group toward acidic conditions. A tautomeric equilibrium involving the stereogenic center induces the product epimerization. The substitution of DMAP and Et 3 N by a highly hindered base, proton-sponge ® , furnished the final products without racemization. The ee of 1 , 2 and of the corresponding methyl esters ( 3 and 4 ) were determined by 1 H NMR analysis in the presence of optically active Eu(tfc) 3 . Epimerization was not observed in the preparation of the carboxylate salts ( 5 – 8 ).

Copper microparticles have been dispersed in anion-exchange polymer films coated on carbon electrodes by oxidative electropolymerization of pyrrole–alkylammonium monomers. Incorporation of copper in polymeric films was effected by impregnation of copper-oxalate anionic complexes followed by an electroreductive precipitation to copper metal, or by electroreduction of polymer coated electrodes immersed in copper–oxalate aqueous solutions. The deposition process was examined by voltammetry. Scanning electron microscopy showed a dispersion of metal particles from 50–100 up to 300 nm, according to the lipophilic character of the polymer, located in a layer near the carbon ∣ polymer interface. A study of the electrocatalytic activity in the reduction of nitrobenzene to aniline at these materials was performed. The cathodes appeared much more active than bulk copper electrodes.

New mono- and 1,1′-bis-amide-linked 2,2′-bipyridine substituted ferrocenyl ligands, L2 and L1, have been prepared. Voltammetric and 1H-NMR investigations of anion binding have been performed. The neutral bis-amide ligand L1 forms a complex with the dihydrogenphosphate anion, and electrochemical recognition of H2PO4− is observed in organic electrolytes. Comparison with the behavior of the mono-amide ligand L2 and of the carboxyester-containing ligands L3 and L4 highlights the benefit of multidentate binding and the importance of hydrogen bonding to amide protons in H2PO4− complexation to L1. The voltammetric behavior of the different ligands in the presence of F−, Cl− and HSO4− can be interpreted mainly in terms of ion pairing with the oxidized, cationic forms of the ligands. In addition, catalytic oxidation of Cl− and oxidative degradation of the ferrocenyl ligands, leading to the formation of [FeIIIClx]3−x species, are observed in the presence of chloride anions.

A new theoretical development based on the concept that the air−water interfacial layer of adsorbed ionic surfactant constitutes a nonautonomous phase is presented. This adsorbed layer can thus be ...

The electrochemical behavior of the pyrrole-substituted crown ether ferrocene 1 was investigated in detail in 0.1 M TBAP+CH 3 CN by cyclic voltammetry (CV) and chronoamperometry. In the potential range 0–0.7 V, a reversible diffusion-controlled process was observed with a formal potential of 0.53 V corresponding to the ferrocene/ferricinium redox couple. Electro-oxidative polymerization of 1 was accomplished either by repeated CV scans, or by controlled potential electrolysis. The resulting polymer films were tested in acetonitrile electrolyte for the amperometric recognition of alkali and alkaline earth metal cations. Their remarkable recognition properties towards Ca 2+ and Ba 2+ cations have been confirmed by electrochemical impedance spectroscopy (EIS). EIS allowed construction of a calibration curve based on the variation of the low frequency capacity of the film as a function of the guest cation concentration, reflecting the variation of the formal potential between the free and the complexed immobilized redox couple. Capacity measurements using EIS appear to be an attractive method for cation sensing with films based on molecular redox receptors.

The electrocatalytic hydrogenation in aqueous electrolyte of acetophenone and 2-butanone with [Rh(L)2Cl2]+ complexes (L is a chiral 2,2′-bipyridine or a 1,10-phenanthroline) has been investigated in homogeneous media or at carbon electrodes coated with thin polymer films prepared by oxidative electropolymerization of a rhodium complex containing a pyrrole-substituted chiral 2,2′-bipyridine ligand. The latter device gave the best results in terms of catalytic efficiency, turnover number (up to 4750) and asymmetric induction (up to 20% ee). From the viewpoint of catalytic efficiency and asymmetric induction, the electrocatalytic system compares well with asymmetric transfer hydrogenation catalyzed by rhodium complexes containing the same ligands.

We describe here a method for coating electrode surfaces with electroactive films by electroreductive precipitation of soluble polymers, synthesized by electrooxidative or photoredox polymerization of polypyridyl ruthenium(II) complexes substituted by pyrrole groups. The redox behaviour of the resulting film modified electrodes is strongly dependent on the size and the lipophilic properties of the ions of the supporting electrolyte. This appears to be a consequence of their permeation through the films to maintain electroneutrality in the polymers.

The electrochemical behavior of tris-substituted bipyridine ruthenium (II) complexes containing the aza-crown-substituted 2,2′-bipyridine ligands L 2 and L 3 (L 2 is 4,4′-disubstituted by 1-aza-18-crown-6 moieties; L 3 is bridged at its 4,4′-positions by a 4,13-diaza-18-crown-6 group), has been studied by cyclic voltammetry in acetonitrile electrolyte, and in the presence of alkali metal cations (Li + , Na + , K + ). Cyclic voltammetry curves show that these complexes are able to recognize potentiometrically a metal cation. The L 2 -based complex is sensitive to Li + and Na + cations, while the L 3 -based complex is only sensitive to the presence of potassium ions. Glassy carbon electrodes have been modified by electropolymerization ofthe related complexes containing pyrrole-substituted bipyridine ligands. The electrochemical behavior of the resulting redox-active films in the presence of the surveyed alkali metal cations shows that the electrochemical recognition properties of these complexes are mainly retained after their immobilization onto an electrode surface, which is a prerequisite to the construction of new prototypes of electrochemical sensor.

The utility of an electrochemical oxidative strategy in the synthesis of expanded porphyrins is demonstrated by the preparation of cyclo[8]pyrrole in high yield via a bipyrrole C(2)-C(2)' coupling process.

Voltammetric and UV spectrophotometric investigations of alkali and alkaline earth metal cations binding by the new ferrocene macrocyclic ligands 1–4 have been performed in acetonitrile electrolyte. Stability constants were determined from UV measurements. All the metal cations surveyed formed 1:1 stoichiometric complexes with 2 and 3 , with the exception of barium which produced a 1:2 intermolecular sandwich complex with 2 . No complexation occurred with 1 . Electrochemical studies have demonstrated that the binding of Li + , Na + , K + , Mg 2+ , Ca 2+ and Ba 2+ with 2 resulted in shifts of the ferrocene oxidation wave to more positive potentials. The same features were observed with 3 in the presence of Li + , Na + , K + and Mg 2+ , and with 4 and Ba 2+ . In contrast, a different type (two-wave behaviour) of positive shift revealed the binding of Ca 2+ and Ba 2+ with 3 , allowing the amperometric titration of these metal cations. The magnitude and the type of potential shift could not be related to the radius and charge to radius ratio of the cations, or to the strength of the host-guest association. It can be assumed that additional effects such as an effective charge transfer interaction between the cationic guest and the redox centre control the electrochemical recognition behaviour of these redox ionophores. Single crystal X-ray structure of [ 3 -Ba](ClO 4 ) 2 has also been determined to gain better understanding of the barium complextion in 3 .

The ability of [( η 5 -C 5 Me 5 )M III (L)Cl] + complexes (M = Rh and Ir. L = 2,2′-bipyridine and 1, 10-phenanthroline) to act as electrocatalysts for the hydrogenation of unsaturated organic substrates has been examined in homogeneous acetonitrile solution, using formic acid as a proton source, as well as in aqueous electrolytes with electrodes modified by oxidative electropolymerization of pyrrole-substituted Rh(III) and Ir(III) complexes. The hydrogenation process involves the formation of an electrogenerated hydrido complex, followed by the insertion of the substrate in the metal-hydride bond. It appears that rhodium complexes are better catalysts than the iridium ones, and that their immobilization onto an electrode surface decreases their catalytic activity.

The self-aggregation properties of a pyrrole-substituted cationic surfactant have been studied using different techniques, including conductivity and surface tension measurements, potentiometry with a surfactant-selective electrode and cyclic voltammetry. Potentiometry gave good results for the determination of its critical micelle concentration (CMC) as well in pure water as in electrolytic media. Furthermore, in spite of the highly irreversible oxidation of the pyrrole group contained in the surfactant, cyclic voltammetry afforded a fast and valuable estimation of the CMC from peak current and peak potential variations.

Functionalized polypyrrole films containing M1(L)(diene)]+ complexes (M = rhodium or iridium, L = substituted 2,2′-bipyridioe or 1,10-phenanthroline) have been synthesized by complexation of [M1(diene)CL)2 precursor complexes in polyL films pre-coated on carbon and platinum surfaces by oxidative electropolymerization of pyrrole-substituted polypyridyl ligands, and characterized by cyclic voltammetry and X-ray photoelectron spectroscopy. The efficiency of the in situ complexation reaction appears strongly dependent on the permeability of the ligand film. The electrochemical behaviour in aqueous electrolyte and the electrocatalytic activity of these metallopolymers towards water reduction and hydrogenation of unsaturated organic substates is described.

Electrochemical oxidation of bis-(N,N′-bisethyl)ferrocene 1,1′-dicarboxamide (1), N,N′-bis-[2-(pyrrole -1 -yl)ethyl]-N,N′-bisethylferrocene)-1,1′-dicarboxamide (2) and N-[2-(pyrrole-1-yl)ethyl] -N-ethylfer-rocene-1-carboxamide (3) was investigated in 0.1 M TBAPCH3CN by cyclic voltammetry (CV) and chronoamperometry. In the potential range of 0–0.6 V a reversible diffusion-controlled process was observed with formal potentials of 0.30, 0.31 and 0.22V, respectively. The diffusion coefficients of 1, 2, and 3 have been evaluated from both CV and chronoamperometric data. Polypyrrole films of 2 and 3 have been obtained potentiostatically (at 0.85–1 V) and by CV on platinum and glassy carbon electrodes in 0.1 M TBAPCH3CN. These films were tested in 0.1 M TBAF4CH3CN, and 0.1 M TMABF4 or LiClO4H2O. The immobilized ferrocene is well characterized in CH3CN by a symmetrical shape signal and also has a satisfactory electrochemical response in water. The influences of monomer concentration and synthesis charge on the modified electrode performances were analysed. The observed linear dependencies of peak current on scan rate and electropolymerization charge in agreement with the power law were discussed.

The electrocatalytic properties of different Mn III Schiff-base complexes in acetonitrile solution in the presence of benzoic anhydride, an axial base and dioxygen have been investigated by cyclic voltammetry. Bulk electrolysis in the presence of cyclooctene yields cyclooctene oxide and shows that the best catalyst complexes (in terms of current efficiency and turnover) are based on ligands containing an ethano (Salen complexes) or a 1,2-cyclohexylidene (Salchx complexes) bridging unit and 5,5′-dichloro substituents. The effect of axial base such as pyridine, collidine, 1- and 2-methylimidazole is shown. The use of the latter base gave the best results for cycloctene epoxidation. Some investigation on tetraline and triphenylphosphine oxidation are also reported.

A new member of the cyclo[n]pyrrole class of expanded porphyrins was prepared from the corresponding thiophene-containing terpyrrole precursor through use of a mild electrochemical oxidative procedure. The isolated macrocycle, featuring nine heterocyclic subunits directly connected through their α,α′-positions, is the largest cyclo[n]pyrrole derivative reported to date. The structure obtained via synchrotron radiation-based studies revealed a dimeric arrangement involving individual macrocyclic subunits.