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Pillar[5]arene derivatives decorated with ten peripheral TTF or exTTF subunits were prepared and their electrochemical properties investigated. These electron-rich macrocyclic systems are suitable receptors for a fullerene guest.

International audience; Fine control of electrografting kinetics of diazonium salts is of paramount importance, particularly when considering the application of diazoniums for the fabrication of 2D nanomaterials. In this work, we develop controlled grafting of a perylenediimide (PDI) moiety separated with a 12-carbon aliphatic chain from aryldiazonium. The particular design of the diazonium cation synthesized for this study allows for fine tuning of the surface coverage by simple adjustment of the applied potential. Indeed, according to the potential imposed at the working electrode, the PDI moiety can either enhance the charge propagation within the growing layer or consume the diazonium salt in the bulk solution via redox cross-reaction. With this approach, the surface functionalization can be restricted to a monolayer or a multilayer in a robust and elegant manner, obeying Langmuir or first-order kinetics of electrografting, respectively. The experimental observations are supported with in situ spectroelectrochemical investigations aimed to differentiate the reduction of PDI moieties in the deposited layer and the bulk solution. A tentative mechanistic scheme is proposed, and numerical simulations are undertaken to rationalize the data.

International audience; Advancing non-fullerene acceptor (NFA) organic photovoltaics requires the mitigation of the efficiency-limiting processes. Acceptor end-group and side-chain engineering are two handles to tune properties, and a better understanding of their specific impact on the photophysics could facilitate a more guided acceptor design. Here, the device performance, energetic landscape, and photophysics of rhodanine and dicyanovinyl end-capped IDT-based NFAs, namely, O-IDTBR and O-IDTBCN, in PCE10-based solar cells are compared by transient optical and electro-optical spectroscopy techniques and density functional theory calculations. It is revealed how the acceptors’ quadrupole moments affect the interfacial energetic landscape, in turn causing differences in exciton quenching, charge dissociation efficiencies, and geminate versus non-geminate recombination losses. More precisely, it is found that the open circuit voltage (VOC) is controlled by the acceptors’ electron affinity (EA), while geminate and non-geminate recombination, and the field dependence of charge generation, rely on the acceptors’ quadrupole moments. The kinetic parameters and yields of all processes are determined, and it is demonstrated that they can reproduce the performance differences of the devices’ current–voltage characteristics in carrier drift-diffusion simulations. The results provide insight into the impact of the energetic landscape, specifically the role of the quadrupole moment of the acceptor, beyond trivial considerations of the donor–acceptor energy offsets.

International audience; A new method to follow in-situ grafting kinetics of diazonium compounds based on imposing small amplitude high frequency AC oscillations at grafting potential, is outlined. This enables the time-resolved measurements of capacitive impedance concomitantly with the growth of the organic layer at the working electrode. The impedance values were quantitatively correlated with the ex-situ (from voltammograms) and in-situ (from quartz crystal microbalance) measured surface coverages, providing a validation of the new methodology. The versatility of the developed approach was demonstrated on the grafting via reduction of 4-nitrobenzenediazonium on Au and glassy carbon (GC) substrates and via deposition of in-situ generated diazonium salts from 1-aminoanthraquinone and 4-ferrocenylaniline on GC. The capacitive impedance measurements are simple, fast, and non-destructive, making it an appealing methodology for an exploration of grafting kinetics of a wide range of diazonium salts.

International audience; A M8L2 metalla-cage constructed through coordination-driven self-assembly from a quinonato bis-ruthenium complex and an electron-rich tetrathiafulvalene (TTF) tetrapyridyl ligand is depicted. In this molecular box, both TTF units are highly bent and are separated by a distance as short as 3.48 Å in the solid state. This system offers a unique opportunity to study the electronic interactions occurring between two TTF units facing each other in a conformationally rigid environment.

International audience; Ultrafast optical control of intramolecular charge flow was demonstrated, which paves the way for photocurrent modulation and switching with a highly wavelength‐selective ON/OFF ratio. The system that was explored is a fac‐[Re(CO)3(TTF‐DPPZ)Cl] complex, where TTF‐DPPZ=4’,5’‐bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2‐a:2’,3’‐c]phenazine. DFT calculations and AC‐Stark spectroscopy confirmed the presence of two distinct optically active charge‐transfer processes, namely a metal‐to‐ligand charge transfer (MLCT) and an intra‐ligand charge transfer (ILCT). Ultrafast transient absorption measurements showed that the ILCT state decays in the ps regime. Upon excitation to the MLCT state, only a long‐lived 3MLCT state was observed after 80 ps. Remarkably, however, the bleaching of the ILCT absorption band remained as a result of the effective inhibition of the HOMO–LUMO transition.

Ultrafast optical control of intramolecular charge flow was demonstrated, which paves the way for photocurrent modulation and switching with a highly wavelength-selective ON/OFF ratio. The system that was explored is a fac-[Re(CO)(3)(TTF-DPPZ)Cl] complex, where TTF-DPPZ = 4’,5’-bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2’,3’-c]phenazine. DFT calculations and AC-Stark spectroscopy confirmed the presence of two distinct optically active charge-transfer processes, namely a metal-to-ligand charge transfer (MLCT) and an intra-ligand charge transfer (ILCT). Ultrafast transient absorption measurements showed that the ILCT state decays in the ps regime. Upon excitation to the MLCT state, only a long-lived (3)MLCT state was observed after 80 ps. Remarkably, however, the bleaching of the ILCT absorption band remained as a result of the effective inhibition of the HOMO–LUMO transition.

International audience; This work presents original methodologies to estimate the electrochemical electron-transfer rate constants (k0) of immobilized electroactive species when strong intermolecular interactions occur in a redox-responsive material, for which the redox reaction is described byButler–Volmer theory. Based on Laviron's equations and the initial Creager and Wooster’s work, these methodologies encompass the general lateral interaction model and have been experimentally tested to estimate k0 in order to provide evidence of the relevance and reliability of our approach.

The dual-analyte responsive behavior of tetraTTF-calix[4]pyrrole receptor 1 has been shown to complex electron-deficient planar guests in a 2:1 fashion by adopting a so-called 1,3-alternate conformation. However, stronger 1:1 complexes have been demonstrated with tetraalkylammonium halide salts that defer receptor 1 to its cone conformation. Herein, we report the complexation of an electron-deficient planar guest, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA, 2) that champions the complexation with 1, resulting in a high association constant Ka = 3 × 1010 M–2. The tetrathiafulvalene (TTF) subunits in the tetraTTF-calix[4]pyrrole receptor 1 present a near perfect shape and electronic complementarity to the NTCDA guest, which was confirmed by X-ray crystal structure analysis, DFT calculations, and electron density surface mapping. Moreover, the complexation of these species results in the formation of a charge transfer complex (22⊂1) as visualized by a readily apparent color change from yellow to b...

International audience; The study of mixed self‐assembled monolayers of perylenediimide and hexanethiol by cyclic voltammetry and absorption spectroelectrochemistry shows a non‐linearity of absorbance maxima as a function of the surface coverage. This surprising result could be supported by an increase in the average tilt angle at low coverage, suggesting that the dilution of redox species through an alkanethiol would induce a change of the orientation of immobilized chromophores and, therefore, a modification of the optical properties of the monolayer.

The synthesis of a redox-active helical foldamer and its immobilization onto a gold electrode are described. These large molecular architectures are grafted in a reproducible manner and provide foldamer-based self-assembled monolayers displaying recognition properties.

International audience; Tetrathiafulvalene redox units were grafted at both extremities of an oligopyridine–dicarboxamide foldamer through a straightforward copper-catalyzed azide–alkyne cycloaddition. The present work demonstrates that the hybridization equilibrium of foldamers can be tuned through redox stimulations.

International audience; High-sensitivity charge coupled-device (CCD) cameras, efficient fibre optic bundles, high stable light source and 3D printing technologies now open large possibilities to probe redox species in solution and on confined surface by real-time absorption spectroelectrochemistry. This short review aims at providing an overview of the first work of absorption spectroelectrochemistry on redox-responsive self-assembledmonolayers (SAMs). Some practical aspects are emphasized to not underestimate the difficulties involved in set-up such instrumentation.

International audience; Electrochemically driven interfacial halogen bonding between redoxactive SAMs and halide anions was quantitatively studied for the first time. The halogen bond donor properties were switched on by electrochemically controlling the oxidation state of the adsorbates. Experimental data and simulation show high binding enhancement towards halide anions compared to homogeneous systems.

From the generalized lateral interactions model and via a few mathematical approximations, a suitable regression function has been developed in order to fit voltammetric peak of redox responsive SAM for extracting the characteristic parameters. The efficiency of the generalized lateral interactions function was tested on simulated and raw data. Keywords: Self-assembled monolayers, Cyclic voltammetry, Lateral interactions, Curve fitting

Postfunctionalization of glassy carbon electrodes previously modified by reduction of 4-azidobenzenediazonium was exploited to conveniently synthesize controlled mixed organic layers. Huisgen 1,3-dipolar cycloaddition was used to anchor functional entities to azide platform. By this way, ((4-ethynylphenyl)carbamoyl)ferrocene (ϕ-Fc) was coimmobilized with a set of acetylene derivatives: 1-ethynyl-4-nitrobenzene (ϕ-NO2), 4-ethynylaniline (ϕ-NH2) or ethylnylbenzene (ϕ). The composition of the resulting organic layers was tuned by adjusting the acetylene derivatives ratio in the postfunctionalization binary solution. Electronic properties of the substituents beared by the aromatic rings were found to have a strong impact on the cycloaddition kinetics toward the confined azide moieties. From this study, rules to prepare finely tuned bifunctional organic layers can be anticipated.

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International audience; A push–pull σ–C60 molecular dyad was synthesized via Huisgen-type click chemistry and used as photoactive material for single-component organic solar cells. Steady-state photoluminescence (PL) experiments of the dyad in solution show a significant quenching of the emission of the push–pull moiety. Spin-casting of a solution of the dyad results in homogeneous and smooth thin films, which exhibit complete PL quenching in line with ultrafast photoinduced electron-transfer in the solid state. Spectroelectrochemistry reveals the optical signatures of radical cations and radical anions. Evaluation of the charge carrier mobility by space-charge limited current measurements gives an electron-mobility of μe = 4.3 × 10–4 cm2 V–1 s–1, ca. 50 times higher than the hole-mobility. Single-component organic solar cells yield an open-circuit voltage Voc of 0.73 V and a short-circuit current density of 2.1 mA cm–2; however, a poor fill factor FF (29%) is obtained, resulting in low power conversion efficiency of only 0.4%. Combined transient absorption (TA) and time-delayed collection field (TDCF) experiments show mostly ultrafast photon-to-charge conversion and a small component of diffusion-limited exciton dissociation, revealing the presence of pure fullerene domains. Furthermore, a strong field dependence of charge generation is observed, governing the device fill factor, which is further reduced by a competition between extraction and fast recombination of separated charges.

International audience; The electrochemical and spectroelectrochemical studies of thienylene vinylene (TV) derivatives in the immobilized state are compared with the ones obtained in solution. The results highlight the exaltation of the dimerization process onto TV-based self-assembled monolayers, in which the π interaction is maintained even after 75% dilution.

We present a spectroelectrochemical bench involving an electrochemical/spectrophotometric coupling dedicated to probe electroactive self-assembled monolayers (SAMs). This bench is validated by the study of the oxidation of a 5,5′-disubstituted-2,2′-bithiophene immobilized on Au substrate, producing a reversible dimerization of the radical cation (i.e. ECDim process) leading to a dimer. A direct comparison between thin layer spectroelectrochemistry in solution and spectroelectrochemistry on SAMs shows that a SAM could be viewed as a highly concentrated solution. Keywords: Self-assembled monolayers, Spectroelectrochemistry, ECDim mechanism, Bithiophene

The {\pi}-{\pi} interactions between organic molecules are among the most important parameters for optimizing the transport and optical properties of organic transistors, light-emitting diodes, and (bio-) molecular devices. Despite substantial theoretical progress, direct experimental measurement of the {\pi}-{\pi} electronic coupling energy parameter t has remained an old challenge due to molecular structural variability and the large number of parameters that affect the charge transport. Here, we propose a study of {\pi}-{\pi} interactions from electrochemical and current measurements on a large array of ferrocene-thiolated gold nanocrystals. We confirm the theoretical prediction that t can be assessed from a statistical analysis of current histograms. The extracted value of t ca. 35 meV is in the expected range based on our density functional theory analysis. Furthermore, the t distribution is not necessarily Gaussian and could be used as an ultrasensitive technique to assess intermolecular distance fluctuation at the subangstr\"om level. The present work establishes a direct bridge between quantum chemistry, electrochemistry, organic electronics, and mesoscopic physics, all of which were used to discuss results and perspectives in a quantitative manner., Comment: Nano Lett (2017), full text and supporting information

A very simple strategy to prepare, in two steps, a versatile and sustainable monolayer platform for on-surface chemistry is presented. The first step consists in the electroreduction of the well-known 4-nitrobenzenediazonium in the presence of a radical scavenger, leading to a covalent monolayer surface modification. Then, a dense reactive phenylamine monolayer is obtained by the full electroreduction of the nitrophenyl moieties. The platform thus obtained is available for post-functionalization with carboxyl derivatives via a usual peptide coupling. Attachment of a TEMPO unit, offering both redox and electrocatalytic properties, validates this approach and leads to high surface coverage and fast electron transfer. A comparison of the electrochemical properties of the modified surface with a classical multilayered post-functionalized one highlights important differences in terms of interfacial reactivity. The results presented here justify the interest of preparing reactive monolayer platform for molecule grafting and opens the way for simple and controlled surface chemistry without the need of synthesis.

This chapter reviews the most recent developments in the fluorescence spectroelectrochemistry, coupled detection of fluorescence and electrochemical signals. It focuses on the instrumental development in fluorescence spectroelectrochemistry and recent coupling of electrochemical techniques with fluorescence microscopy. The first part is dedicated to conventional fluorescence spectroelectrochemistry cells and the second one to the electrochemistry and fluorescence microscopy coupling.

International audience; A proof-of-concept related to the redox-control of the binding/releasing process in a host-guest system is achieved by designing a neutral and robust Pt-based redox-active metallacage involving two extended-tetrathiafulvalene (exTTF) ligands. When neutral, the cage is able to bind a planar polyaromatic guest (coronene). Remarkably, the chemical or electrochemical oxidation of the host-guest complex leads to the reversible expulsion of the guest outside the cavity, which is assigned to a drastic change of the host-guest interaction mode, illustrating the key role of counteranions along the exchange process. The reversible process is supported by various experimental data (1 H NMR spectroscopy, ESI-FTICR, and spectroelectrochemistry) as well as by in-depth theoretical calculations performed at the density functional theory (DFT) level.

The effect of a radical scavenger (DPPH: 2,2-diphenyl-1-picrylhydrazyl) on the spontaneous covalent grafting of nitrophenyl functionalities on a vitreous carbon substrate using the 4-nitrobenzene diazonium cation has been studied by electrochemical measurements and X-ray photoelectron spectroscopy. The addition of micromolar concentrations of DPPH to the diazonium solution efficiently limits the multilayer formation and leads to monolayer surface coverage. Control of polyaryl layer formation via the capture of the reactive nitrophenyl radical was also found to increase the proportion of nitrophenyl groups grafted to the surface via azo bridges. This work validates the recently reported strategy using a radical scavenger to prevent the formation of a polyaryl layer without interfering with direct surface grafting.

The lateral interactions model, dedicated to random and non-random distributed electroactive species on redox responsive self-assembled monolayers (SAM), was extended to interactions between redox and non-redox species. This approach supports an unusual result achieved in the field of electrochemical transduction without covalent links between redox and complexant units in mixed SAM. Keywords: Self-assembled monolayers, Cyclic voltammetry, Lateral interactions, Redox interactions, Non-redox interactions

A simple strategy to avoid the formation of polyaryl layer during the functionalization of carbon surface by diazonium electroreduction is presented. The approach proposes to directly act on the polymerization mechanism by the use of a radical scavenger. The kinetic gap between the surface coupling and the multilayer formation is exploited to prevent the growth of the layer without interfering with the grafting. The well-known 4-nitrobenzenediazonium electrografting was used to demonstrate the possibility of reaching a monolayer surface coverage with an excess of DPPH (2,2-diphenyl-1-picrylhydrazyl). Experimental conditions were varied to validate the efficiency of the grafting limitation and the radical capture was confirmed by isolation of the aryl radical/DPPH coupling product.

The electrochemical behavior of redox centers on self-assembled monolayer (SAM) was interpreted through the generalized lateral interactions model when the electrolyte medium is composed of miscible solvents.Electrochemical behaviors of nitroxyl radical SAMs provide evidence of a linear dependence of interaction parameters with the ratio of the two solvents. Keywords: TEMPO, Self-assembled monolayers, Cyclic voltammetry, Lateral interactions model

International audience; The discovery of conducting lithium-doped polyaniline with reversible redox chemistry allows simultaneous unprecedented capacity and stability in a non-aqueous Li battery. This compound (lithium emeraldinate) was synthesized by lithium–proton exchange on the emeraldine base in an anhydrous lithium-based electrolyte. A combination of UV/Vis-NIR spectroelectrochemistry, XPS, FTIR, and EQCM characterization allowed a unified description of the chemical and electrochemical behavior, showing facile charge delocalization of the doped states and the reversibility of the redox processes in this form of polyaniline. From a practical point of view, lithium emeraldinate behaves as a high-capacity organic active material (230 mAh g−1) that enables preparation of relatively thick composite electrodes with a low amount of carbon additives and high energy density (460 Wh kg−1). Concomitantly, at 1C rate, 400 cycles were achieved without significant capacity loss, while the coulombic efficiency is greater than 99 %.

International audience; A series of diazonium salts bearing different para substituents was used to functionalize glassy carbon (GC) and pyrolyzed photoresist film (PPF) under electrografting conditions in the absence and presence of the radical scavenger diphenyl-1-picrylhydrazyl (DPPH). Depositions were monitored by electrochemical quartz crystal microbalance (EQCM) and the grafted layers were analyzed by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). DPPH was used to selectively suppress film growth by radical coupling and thereby to reveal the existence of secondary mechanisms involved in the polymerization. Differences in grafting behaviors between various diazonium ion derivatives can be explained by the influence of the para substituent’s electronic properties on the electrophilic aromatic substitutions of diazonium ions on already grafted aromatic groups.

International audience; Perylenediimide (PDI) based self-assembled monolayers (SAMs) have been studied by quartz crystal microbalance, X-ray photoelectron spectroscopy, cyclic voltammetry and spectroelectrochemistry (SEC). The high stability of PDI based SAMs has allowed probing very low signals by absorption and emission SEC and extracting voltabsorptograms. The wavelengths of absorption maxima of PDI, anion radical and dianion species. In contrast, the magnitudes of the molar extinction coefficient of the reduced forms were not preserved in SAM. The quenching of PDI fluorescence was confirmed on gold substrate.

International audience; Mainly based on electrochemical investigations, this work provides evidence of discrimination between self-assembled monolayers (SAMs) prepared from alkanethiols or symmetrical dialkyl disulfides on gold. Gravimetric experiments carried out by quartz crystal microbalance during the elaboration of ferrocene based SAMs (from alkanethiols FcC15SH and dialkyl disulfides FcC15SSC15Fc), showed significant differences between monolayers made from the two precursors. The recorded mass was almost 60 % more important with FcC15SH by comparison with FcC15SSC15Fc. The resulting cyclic voltammograms also highlighted a 60 % difference concerning the surface coverage of ferrocene heads. Moreover, dialkyl disulfide and thiol anchoring groups led to symmetrical and dissymmetrical peaks, respectively, suggesting not insignificant differences concerning interactions between adsorbed species into the two kinds of elaborated monolayers. These observations were confirmed on SAMs obtained from other precursors possessing shorter chain length or another functional moiety.

International audience; To intimately combine a chelating ligand function with the numerous properties of a viologen-like redox-active centre would offer a rare possibility to design controllable multi-redox states, whose properties arise from strongly correlated phenomena between the organic ligand as well as with any metalloid coordinated centres. Such a concept previously proved to be feasible, however is not widely applicable owing to challenges in terms of synthesis, isolation, and aerial sensitivity of both the ligand and its metal complexes. Here we report the first stable example of such a redox-active molecule, N,N′-dimethyl-3,3′-biquinoxalinium2+/˙+/0 “methylbiquinoxen, MBqn2+/˙+/0”, which shows a rich redox chemistry and chelates a metal ion in the case of the metal complex [CdCl2(MBqn0)]. This goes beyond what is possible to achieve using viologens, which are limited by not providing chelation as well as having no accessible biradicaloid state, corresponding to the neutral direduced MBqn0 open-shell behaviour we observe here.

International audience; Electrocatalytic behavior of TEMPO derivative SAMs on gold has been studied in the presence of benzyl alcohol. The results demonstrate that interfacial activity of the SAMs can be enhanced by diluting the TEMPO moiety with an alkyl passive matrix. The absolute catalytic activity exhibits a maximum for an intermediate value of the surface coverage of catalytic centers. The most significant feature is the monotonic increase of the turnover (relative activity) until a limit value reached for low TEMPO surface concentrations. The electrocatalytic performances seem to be governed by a combination of two factors: the physical accessibility (by alcohol molecules in solution) and the regeneration (via the comproportionation of oxoammonium and hydroxylamine before electrochemical reoxidation) of the catalytic centers. ■ INTRODUCTION Self-assembled monolayers (SAMs) of thiolate derivatives have been widely studied and are known to form well-organized structures on various substrates. 1 The self-organization of monolayers leads to packed structures and allows high surface coverage. 2 Employing redox SAM-modified electrodes for catalysis, recognition, and sensing has resulted in some elegant examples that incorporate sophisticated receptors on the electrode surfaces. 3,4 However, one of the limitations of such architecture is the low structural quality exhibited by the monolayers when the structure-building forces are disturbed by the use of bulky active elements. In such cases, the strong interactions between the head groups result in poorly organized SAMs and possible ungrafted zones. 5 A second disadvantage can come from the strong mutual interactions of the functional groups in confined spaces. Indeed, the transposition of the properties of an active moiety from the solution to the surface can only be successful if the available space around the immobilized active center is sufficient. 6 Few works have resorted to the elaboration of mixed SAMs in order to favor active molecule accessibility 7 or enhance its stability, 8 but, to the best of our knowledge, quantification of the interfacial activity of an immobilized center as a function of its surface concentration has not been examined in detail. The present study investigates the reactivity of TEMPO derivative SAMs and mixed SAMs toward the electrocatalytic oxidation of benzyl alcohol in solution. Our goal was to demonstrate that interfacial activity of the SAMs can be enhanced by diluting the TEMPO moiety with an alkyl passive matrix. ■ EXPERIMENTAL SECTION Au substrates were prepared by deposition of ca. 5 nm of chromium followed by ca. 100 nm of gold onto a glass substrate through a shadow mask (MECACHIMIQUE/France) using physical vapor deposition system (PVD ME300 PLASSYS/France) and were made immediately before use. This protocol provides reproducible Au(111) surfaces with high crystallographic quality, low roughness (Ra less than 2 nm). They do not undergo post-treatment after completion. Mixed SAMs were elaborated by successive adsorptions of aminoxylalkanethiol C15T (Scheme 1) and dodecanethiol C12. Synthesis and characterization of C15T were described in ref 9 and dodecanethiol was used as received from Sigma-Aldrich. Cyclic voltammetry (CV) was performed in a three-electrode cell controlled at a temperature of 293K. Working electrodes were functionalized Au substrates. Counter electrodes were platinum plates. Reference electrodes were Ag/AgNO 3 (0.01 M CH 3 CN). Cyclic voltammograms were recorded in dry HPLC-grade dichloromethane (CH 2 Cl 2) and the supporting electrolyte was tetrabutylammonium hexafluorophosphate (Bu 4 NPF 6). X-ray photoelectron spectroscopy (XPS) data have been collected using a Kratos Axis Ultra spectrometer. The X-ray source is Al K working at 1486.6 eV and using a spot size of 0.7 × 0.3 mm 2. Semiquantitative XPS analysis has been performed using a pseudo-Voigt function constrained by full width at half-maximum (fwhm) Scheme 1. Derivative of TEMPO Radical: C15T Article pubs.acs.org/Langmuir

International audience; The synthesis of five light absorbing triazolobithiophenic thiols, which were utilized for producing self-assembled monolayers (SAMs) on gold surfaces, is presented. The monolayer formation was monitored by cyclic voltammetry, indicating excellent surface coverage. The new triazolobithiophenic compounds exhibited an absorption maximum around 340 nm, which is close to the emission wavelength of a standard nitrogen laser. Consequently these compounds could be used to aid ionization in laser desorption mass spectrometry (MS).

Within the last 25 years, matrix-assisted laser desorption ionization (MALDI) has become a powerful analytical tool in mass spectrometry (MS). While the method has been successfully applied to characterize large organic molecules such as proteins, sugars and polymers, its utilization for small molecules (≤ 600 Da) is significantly impaired by the coformation of matrix ions. Reducing or eliminating matrix-related signals has been subject of many studies. Some of which propose the enhancement of so-called matrix suppression effects, while others suggest the replacement of matrix molecules by materials such as microporous silicon. Alternatively, the immobilization of matrix molecules by utilizing them as self-assembled monolayers (SAMs) has been discussed. In continuation of this research, the current manuscript focuses on the elucidation of ion formation processes occurring on the surface of light absorbing SAMs. Ion yields obtained by free and immobilized matrix molecules as well as those generated by matrix-free gold film-assisted laser desorption ionization (GF-LDI) were compared. Experiments showed that the formation of strong analyte signals essentially required the presence of free matrix molecules, while the immobilization of the latter severely impaired ionization. The observed effect inversely correlated with the surface coverage of SAMs determined by cyclic voltammetry (CV). Based on these findings, the MS signal generated on light absorbing SAMs could be used supplementary to CV for determining the surface coverage of light absorbing SAMs. Copyright © 2011 John Wiley & Sons, Ltd.

International audience; Highly selective formation of 2+2 macrocycle 1 from 2,5-bis(3-formyl-2-hydroxyphenyl)-1,3,4-oxadiazole and a diamine-functionalized tetrathiafulvalene derivative is reported. Its electronic properties have been studied experimentally by the combination of electrochemistry and UV-vis-NIR spectroscopy. Particularly, its largely extended pi-conjugation renders this novel macrocycle simultaneously a good multielectron donor and a strong chromophore, which is rationalized on the basis of density functional theory. (C) 2011 Elsevier Ltd. All rights reserved.

A tetrathiafulvalene donor has been annulated to 2,3-di(1H-2-pyrrolyl)quinoxaline affording a new chemosensor 1, which shows a unique optical selectivity and reactivity for the fluoride ion over other anions in CH2Cl2 leading to a colorimetric response. Electrochemical polymerization of 1 occurred in the presence of fluoride.

The Laviron's interaction model, dedicated to randomly distributed electroactive adsorbed species, was extended to a non-random distribution in order to extract the current–voltage characteristics from any surface distribution of electroactive centers on self-assembled monolayer (SAM). Confronted to electrochemical behaviour of nitroxyl radical SAMs, the agreement observed between theory and experiments provides evidence of a distribution independence of the interaction parameters. Keywords: Tempo, Self-assembled monolayers, Cyclic voltammetry, Interaction model

To study the electronic interactions in donor-acceptor (D-A) ensembles, D and A fragments are coupled in a single molecule. Specifically, a tetrathiafulvalene (TTF)-fused dipyrido[3,2-a:2',3'-c]phenazine (dppz) compound having inherent redox centers has been synthesized and structurally characterized. Its electronic absorption, fluorescence emission, photoinduced intramolecular charge transfer, and electrochemical behavior have been investigated. The observed electronic properties are explained on the basis of density functional theory.

International audience; This paper analyzes the impact of the use of a radical scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.

We propose a versatile function to fit adsorption voltammetric peak in order to extract the characteristic parameters such as the full width at half maximum, the peak potential, the peak current and the surface coverage. Based on the generalized Gaussian function and supported by generalized lateral interaction model, this method has been tested on different electroactive self-assembled monolayers (i.e. ferrocene, bithiophene, tetrathiafulvalene and radical aminoxyl units). Keywords: Self-assembled monolayers, Cyclic voltammetry, Lateral interactions, Generalized Gaussian function

International audience; This work presents an original strategy to modulate the electrochemical properties of the indolino[2,1-b]oxazolidine core appropriately substituted in position 5 (para-substitution of the phenyl ring) by acceptor or donor groups (CHO, OMe, Me, F, H, Cl, Br). Supported by spectroelectrochemical experiments and confronted to electrochemical simulations, the stepwise oxidation of indolino[2,1-b]oxazolidine derivatives involves an electrochemical mechanism which depends on the para-substitution of the phenyl ring and leads to either the formation of a stable radical cation, the opening of the oxazolidine ring or an irreversible aryl C–C coupling.