Lionel Sanguinet

Unraveling unprecedented charge carrier mobility through structure property relationship of four isomers of didodecyl[1]benzothieno[3,2-b][1]benzothiophene

The structural and electronic properties of four isomers of didodecyl[1]-benzothieno[3,2-b][1]benzothiophene (C12-BTBT) have been investigated. Results show the strong impact of the molecular packing on charge carrier transport and electronic polarization properties. Field-induced time-resolved microwave conductivity measurements unravel an unprecedented high average interfacial mobility of 170 cm(2) V(-1) s(-1) for the 2,7-isomer, holding great promise for the field of organic electronics.

Star-Shaped Tetrathiafulvalene-Fused Coronene with Large π-Extended Conjugation

A tristar shaped, planar TTF-fused coronene 1 was synthesized. Its electronic properties have been studied experimentally by the combination of electrochemistry and UV-vis-NIR spectroscopy. Thereby, a nanosized graphite fragment is largely extended in its size, supplemented with a multielectron donor functionality, and shaped to a strongly chromophoric species absorbing intensely in the visible part of the optical spectrum.

Tuning a 96-Well Microtiter Plate Fluorescence-Based Assay to Identify AGE Inhibitors in Crude Plant Extracts

Advanced glycation end-products (AGEs) are involved in the pathogenesis of numerous diseases. Among them, cellular accumulation of AGEs contributes to vascular complications in diabetes. Besides using drugs to lower blood sugar, a balanced diet and the intake of herbal products potentially limiting AGE formation could be considered beneficial for patients’ health. The current paper presents a simple and cheap high-throughput screening (HTS) assay based on AGE fluorescence and suitable for plant extract screening. We have already implemented an HTS assay based on vesperlysines-like fluorescing AGEs quickly (24 h) formed from BSA and ribose under physiological conditions. However, interference was noted when fluorescent compounds and/or complex mixtures were tested. To overcome these problems and apply this HTS assay to plant extracts, we developed a technique for systematic quantification of both vesperlysines (λexc 370 nm; λem 440 nm) and pentosidine-like (λexc 335 nm; λem 385 nm) AGEs. In a batch of medicinal and food plant extracts, hits were selected as soon as fluorescence decreased under a fixed threshold for at least one wavelength. Hits revealed during this study appeared to contain well-known and powerful anti-AGE substances, thus demonstrating the suitability of this assay for screening crude extracts (0.1 mg/mL). Finally, quercetin was found to be a more powerful reference compound than aminoguanidine in such assay.

Tetrathiafulvalene-Fused Porphyrins via Quinoxaline Linkers: Symmetric and Asymmetric Donor–Acceptor Systems

A tetrathiafulvalene (TTF) donor is annulated to porphyrins (P) via quinoxaline linkers to form novel symmetric P-TTF-P triads 1 a-c and asymmetric P-TTF dyads 2 a,b in good yields. These planar and extended π-conjugated molecules absorb light over a wide region of the UV/Vis spectrum as a result of additional charge-transfer excitations within the donor-acceptor assemblies. Quantum-chemical calculations elucidate the nature of the electronically excited states. The compounds are electrochemically amphoteric and primarily exhibit low oxidation potentials. Cyclic voltammetric and spectroelectrochemical studies allow differentiation between the TTF and porphyrin sites with respect to the multiple redox processes occurring within these molecular assemblies. Transient absorption measurements give insight into the excited-state events and deliver corresponding kinetic data. Femtosecond transient absorption spectra in benzonitrile may suggest the occurrence of fast charge separation from TTF to porphyrin in dyads 2 a,b but not in triads 1 a-c. Clear evidence for a photoinduced and relatively long lived charge-separated state (385 ps lifetime) is obtained for a supramolecular coordination compound built from the ZnP-TTF dyad and a pyridine-functionalized C(60) acceptor unit. This specific excited state results in a (ZnP-TTF)(⋅+) ⋅⋅⋅(C(60) py)(⋅-) state. The binding constant of Zn(II) ⋅⋅⋅py is evaluated by constructing a Benesi-Hildebrand plot based on fluorescence data. This plot yields a binding constant K of 7.20×10(4)  M(-1), which is remarkably high for bonding of pyridine to ZnP.

Self-assembled monolayers of mono-tetrathiafulvalene calix[4]pyrroles and their electrochemical sensing of chloride.

Since the first reports more than a half-century ago, interest in self-assembled monolayers (SAMs) on metal surfaces has increased almost exponentially. At present, such supported SAMs are used for numerous applications, ranging from metallurgy—wherein the surface properties, such as conductivity, wettability, corrosion resistance, and etching resistance, are modified—to the preparation of sensors and materials for use in separations. In fact, the use of SAMs is now recognized as offering a convenient, flexible, and simple way to tailor the interfacial properties of metals. This is because the spontaneous organization and absorption of molecules on metal, metal oxide, or semiconducting surfaces often creates highly ordered systems with well-defined dimensions on the nanoscale. During the last decade, increasing attention has been dedicated to the design and elaboration of SAMs that integrate a molecular or ionic receptor unit with a transducer element so as to create sensing devices for environmental or biologic purposes. If a redox-active element is incorporated into the monolayer or the guest, the recognition event can be followed by cyclic voltammetry (CV). In other cases, the monitoring can be completed by using impedance spectroscopic measurements. Although, cation (generally metallic ions) recognition using SAMs is well documented, and several systems that exhibit both excellent selectivity and sensitivity have been described in the literature, much less work on anion recognition by using SAMs has been reported, perhaps reflecting the fact that anions have variable sizes and shapes and exhibit strong solvation in most solvents. The first anion recognition SAM systems were reported by Astruc et al. and involved the use of ferrocene derivatives for dihydrogenophosphate anion detection. More recently, Echegoyen et al. described SAMs for use in acetate anion recognition. Although these systems are very selective, their sensitivity is relatively low and the limits of detection do not reach the sub-millimolar scale. Calix[4]pyrrole and its derivatives have been extensively studied in the search for chemosensors capable of recognizing specific chemical species, with a number of optically active calix[4]pyrrole-based sensors having now been reported. Some of us have recently described the first fully successful examples of electrochemically active sensors based on calix[4]pyrroles; these were prepared by attaching one, two, or four redox-active tetrathiafulvalene (TTF) units directly to the calix[4]pyrrole platform so as to produce receptors with enhanced binding affinities toward anions as compared to the parent meso-octamethyl calix[4]pyrrole. In the case of the mono-TTF calix[4]pyrrole, we observed selectivity between the chloride anion (Ka= 2900m ) and the bromide anion (Ka=96m ) in CH2Cl2 solution. This success has led us to consider that TTF calix[4]pyrroles could be used to create anion-sensing SAMs. These kinds of receptors are attractive in this regard because they incorporate within one molecular framework both pyrrolebased anion recognition and TTF-derived transducer subACHTUNGTRENNUNGunits. We wish to report here that such SAMs may be prepared and that they are effective for chloride anion recognition at the sub-millimolar level, thus providing a sensitivity that differs dramatically from previously reported systems. [a] L. G. Jensen, Dr. K. A. Nielsen, Prof. J. O. Jeppesen Department of Physics and Chemistry University of Southern Denmark Campusvej 55, DK-5230, Odense M (Denmark) Fax: (+45)6615-8780 E-mail : joj@ifk.sdu.dk Homepage: http://www.jojgroup.sdu.dk [b] Dr. T. Breton, Prof. Dr. E. Levillain, Dr. L. Sanguinet Universit d’Angers—CNRS 2 boulevard Lavoisier 49045, Angers Cedex (France) E-mail : eric.levillain@iniv-angers.fr lionel.sanguinet@univ-angers.fr [c] Prof. J. L. Sessler Department of Chemistry and Biochemistry The University of Texas at Austin 1 University Station, A5300, Austin, TX 78712-0165 (USA) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.200901394.

Indolinooxazolidine: a versatile switchable unit.

The design of multiresponsive systems continues to arouse a lot of interest. In such multistate/multifunctional systems, it is possible to isomerize a molecular system from one metastable state to another by application of different stimulation such as light, heat, proton, or electron. In this context, some researches deal with the design of multimode switch where a same interconversion between two states could be induced by using indifferently two or more different kind of stimuli. Herein, we demonstrate that the association of an indolinooxazolidine moiety with a bithiophene unit allows the development of a new trimode switch. A reversible conversion between a colorless closed form and a colorful open form can be equally performed by light, proton, or electrical stimulation. In addition, the oxidation of this system allows the generation of a third metastable state.

Synthesis and characterization of isomerically pure anti- and syn-anthradiindole derivatives

Synthesis, isolation, and characterization of isomerically pure syn- and anti-anthradiindole (ADI) derivatives are described. The anti- and syn-ADI structures are demonstrated by (13)C NMR spectroscopy and by single-crystal X-ray diffraction. The spectroscopic and electrochemical properties as well as the stability of these newly synthesized π-conjugated systems are evaluated and supported by quantum-chemical calculations.

Huge electro-/photo-/acidoinduced second-order nonlinear contrasts from multiaddressable indolinooxazolodine.

In this work, linear and nonlinear optical properties of electro-/acido-/photoswitchable indolino[2,1-b]oxazolidine derivatives were investigated. The linear optical properties of the closed and open forms have been characterized by UV-visible and IR spectroscopies associated with DFT calculations. Nonlinear optical properties of the compounds have been obtained by ex situ and in situ hyper-Rayleigh experiments in solution. We show that protonated, oxidized, and irradiated open forms exhibit the same visible absorption and NLO features. In particular, the closed and open forms exhibit a huge contrast of the first hyperpolarizability with an enhancement factor of 40-45. Additionally, we have designed an original electrochemical cell that allows to monitor in situ the hyper-Rayleigh response upon electrical stimulus. We report notably a partial but good and reversible NLO contrast in situ during oxidation/reduction cycles. Thereby, indolinooxazolidine moieties are versatile trimodal switchable units which are very promising for applications in devices.

Silica-mediated synthesis of indolinooxazolidine-based molecular switches.

A novel and convenient method for the synthesis of photochromic compounds is reported here. It is based on the use of commercially available untreated silica, as an efficient catalyst to perform the condensation between indolinooxazolidine derivatives and aromatic aldehydes under solvent-free conditions. The scope and limitations of this transformation were investigated and several novel photochromic indolinooxazolidines were synthesized. This methodology can also be applied to the synthesis of other photoactive compounds such as spiropyrans or spirooxazines. According to our working protocol the reaction did not require any solvent or additional reagents and gave the products within 10 min in isolated yields of up to 90%.

Evaluation of a new matrix-free laser desorption/ionization method through statistic studies: comparison of the DIAMS (desorption/ionization on self-assembled monolayer surface) method with the MALDI and TGFA-LDI techniques

This work demonstrates that the desorption/ionization on self-assembled monolayer surface (DIAMS) mass spectrometry, a recent matrix-free laser desorption/ionization (LDI) method based on an organic target plate, is as statistically repeatable and reproducible as matrix assisted laser desorption ionization (MALDI) and thin gold film-assisted laser desorption/ionization (TGFA-LDI) mass spectrometries. On lipophilic DIAMS of target plates with a mixture of glycerides, repeatability/reproducibility has been estimated at 15 and 30% and the relative detection limit has been evaluated at 0.3 and 3 pmol, with and without NaI respectively. Salicylic acid and its d(6)-isomer analysis confirm the applicability of the DIAMS method in the detection of compounds of low molecular weight.