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Lead was found to efficiently mediate the allylation reactions of carbonyl compounds with cyclic allylic halides in the presence of stoichiometric amounts of lithium chloride and a catalytic amount of GaCl3 (20 mol %), leading to the desired homoallylic alcohols in modest to high yields with excellent diastereocontrol (>99:1 syn/anti) and good functional group tolerance. In contrast, the use of either 2-pyridinecarboxaldehyde as the carbonyl substrate or ( E)-cinnamyl bromide as the allylating agent produced the corresponding product with reversed diastereoselectivity (>99:1 anti/syn). Nanyang Technological University We gratefully acknowledge the financial support from Nanjing Tech University (Start-up grant nos. 39837118, 39837101, and 39837146), the SICAM Fellowship from Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Forestry University, and Nanyang Technological University.

An efficient method for the synthesis of alkyl indium reagents by means of an indium(III) or lead(II) halidecatalyzed direct insertion of indium into alkyl iodides and their applications in palladium-catalyzed crosscoupling reactions with aryl halides is developed. NMR and ESI-MS analyses indicated that rather than the formation of the commonly recognized alkyl indium sesquihalide with the formulation of R3In2X3, the formed alkyl indium reagent in the present protocol should be a mixture of an alkyl indium dihalide (RInX2) and a dialkyl indium halide (R2InX) (both of them presumably exist as dimers). Nanyang Technological University We gratefully acknowledge the financial support from the Nanjing Tech University (Start-up Grant No. 39837118, 39837101, and 39837146), the SICAM Fellowship from the Jiangsu National Synergetic Innovation Center for Advanced Materials, and the Nanyang Technological University.

The axially chiral ligand of R-BINOL scaffold was synthesized by a series of manipulations which involved different chemical reactions to obtain the desired sliver(I) and gold(I) $$\{[\hbox {L}(\hbox {L}'\hbox {-NHC})_{2}]\hbox {M}\}\hbox {Cl}$$ ( $$\hbox {L} = 3{,}3'\hbox {-dimethyl-2}{,}2'\hbox {-dimethoxy-1,1}'\hbox {-binaphthyl}, \hbox {L}' = i\hbox {-propyl-benzo}[\hbox {d}]\hbox {imidazole})$$ (M =Ag and Au) complexes. Enantiopure R-BINOL was employed as a basic unit to synthesize a benzimidazole based bis-NHC ligand 1g which was obtained through the formation of different intermediate 1(a-f) compounds. The newly synthesized bis-NHC ligand precursor (1g) and its corresponding $$\{[\hbox {L}(\hbox {L}'\hbox {-NHC})_{2}]\hbox {Ag}\}\hbox {Cl}$$ (1h) and $$\{[\hbox {L}(\hbox {L}'\hbox {-NHC})_{2}]\hbox {Au}\}\hbox {Cl}$$ (1i) complexes were characterized by different spectroscopic techniques. The geometries of the optimized structure of the complexes 1h and 1i were computed at the B3LYP/SDD, 6-31G(d) level. Low temperature fluorescence spectroscopic studies did not show any evidence for the weak metal-metal interaction in these complexes. SYNOPSIS Synthesis, characterization of $$\{[\hbox {L}(\hbox {L}'\hbox {-NHC})_{2}]\hbox {M}\}\hbox {Cl}$$ (M = Ag and Au) (1h) and (1i) type sliver(I) and gold(I) complexes are reported. Molecular structures of these benzimidazole based, axially chiral complexes of R-BINOL scaffolds were determined by the computational studies. The results of spectroscopic and analytical data as well as the computational study show that the ligand (1g) prefers to form mononuclear bis-NHC silver(I) and gold(I) complexes in the given conditions.

In this article a convenient method for the synthesis of novel piperazine based bis(4-hydroxy-2H-chromen-2-one) derivatives using pyrazine-1,4-diium tricyanomethanide {[1,4-DHPyrazine][C(CN)(3)](2)} as a new nanostructured molten salt (NMS) catalyst has been described. These compounds were synthesized via Mannich type reaction between several aromatic aldehyde, piperazine and 4-hydroxycoumarin under solvent-free condition at room temperature. The NMS catalyst was fully characterized via Fourier transform infrared (FT-IR), nuclear magnetic resonance (H-1 NMR and C-13 NMR), mass spectrometry, thermal gravimetric, derivative thermal gravimetric, differential thermal analysis, X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy analysis. The new compounds synthesized by using this NMS catalyst were also characterized by FT-IR, H-1 NMR and C-13 NMR, high-resolution mass spectrometry techniques. The new NMS catalyst simply recovers and can be reused several times without significant loss of catalytic activity. The major advantages of the described method in comparison to the classical reactions are low catalyst loading, short reaction time, high yields, simple isolation of product and reusability of the NMS catalyst.Pyrazine-1,4-diium tricyanomethanide as a nano molten salt catalyst was designed, synthesized and used for the synthesis of novel biological piperazine based bis(4-hydroxy-2H-chromen-2- one) derivatives as bioactive and drug candidates.[GRAPHICS].

A comprehensive study of the self-assembly in water of a lipopeptide consisting of a sequence of L-proline, L-arginine and L-tryptophan with a hydrocarbon chain has been performed. Fluorescence assays were used to determine the critical aggregation concentration. In situ small-angle X-ray scattering (SAXS) and molecular dynamics simulations showed the presence of spherical micelles with diameters around 6 nm. In agreement with these results, cryo-TEM images showed globular aggregates with diameters ranging from ≈4 nm up to ≈9 nm. Furthermore, the lipopeptide catalytic activity has been tested for the direct aldol reaction between cyclohexanone and p-nitrobenzaldehyde, and we have observed that the self-association of the organocatalyst played a critical role in the enhanced activity. Water affects the selectivity, and poor results are obtained under neat reaction conditions. The location of the catalytic groups at the lipopetide/water solvent interface also endowed unusual selectivity in the catalyzed aldol reactions. Under optimized reaction conditions, high yields (up to >99%), good enantioselectivity (ee up to 85%) and high diastereoselectivity (ds up to 92 : 8) were obtained.

For the first time, a facile, ultrafast, ammonia-driven microwave-assisted synthesis of high-quality nitrogen-doped graphene quantum dots (NGQDs) at room temperature and atmospheric pressure is presented. This one-step method is very cheap, environment friendly, and suitable for large-scale production. The as-synthesized NGQDs consisting of one to three graphene monolayers exhibit highly crystalline quality with an average size of 5.3 nm. A new fluorescence (FL) emission peak at 390 nm is observed, which might be attributed to the doped nitrogen atoms into the GQDs. An interesting red-shift is observed by comparing the FL excitation spectra to the UV-visible absorption spectra. Based on the optical properties, the detailed Jablonski diagram representing the energy level structure of NGQDs is derived.

International audience; The process of cationic polymerization of p-methoxystyrene in emulsion using recently discovered water dispersible Lewis acid surfactant complexes (LASCs) has been investigated in detail. These latter are prepared from specific branched sodium dodecylbenzenesulfonate and different metal salts (namely ytterbium, scandium, and indium). First, the reaction rate increases while changing the nature of Yb salt in the range Yb(OTf)(3) > YbEr3 > YbCl3 > Yb(NO3)(3). The nature of metal was also shown to influence the propagation rate, with a fair acceleration of the polymerization when using indium or scandium ions. Raising the temperature led also to an increase of the reaction rate, but the molar mass of obtained polymers decreased. It was also demonstrated that the use of an appropriate initiator (pentachlorophenol) allows controlling to some extent the molar mass of synthesized polymers. Polymer characterization by H-1 NMR spectroscopy revealed a significant fraction of olefinic end groups, indicating that the main chain-breaking process is via chain transfer reactions. All these results are consistent with a mechanism where polymerization proceeds inside the monomer droplets.

Three novel C 3-symmetric tris-salicylaldimine Schiff base based “off-on” fluorescence sensors have been designed and synthesized. The synthetic approach involves a simple imine bond (C = N) formation between 1,3,5-tris(4’-aminophenyl)benzene (TAPB) and 3,5-substituted salicylaldehydes. The presence of salicylaldehyde units on periphery of the tris-salicylaldimine Schiff bases masks the fluorescence of TAPB core. Interestingly, binding of fluoride ions to the salicylaldehyde units turns the fluorescence “on” in visible region. Fluoride ion detection limits for the present sensors have been calculated to be in the range of 0.17–3.0 ppm, which depends on the nature of the salicylaldehyde units.

International audience; Enzymatically catalyzed reactions are highly efficient but higher scale extrapolation is limited to a certain class of stable and easily recyclable enzymes. Homogeneously and/or heterogeneously catalyzed reactions are often limited by the multiphasic nature of catalytic systems and/or variations in the distribution of active sites. For these reasons, the development of highly selective and efficient hybrid catalysts is especially needed, and it is now well admitted that disruptive innovation is highly desirable in process engineering, (bio)catalyst design and materials science. Optimal integration of all types of catalysis is the key for efficient global implementation of sustainable processes. This review gives an overview of all the pathways that integrate chemical and biological catalysis, beginning with combined chemoenzymatic processes in cascade to progressively open the field of hybrid catalysis in a one-pot concomitant execution. We have emphasized the factors that have to be considered to understand the catalytic synergy between these systems. A better understanding of hybrid catalytic systems is an essential tool not only in the choice of the best route of their implementation but also in the synthesis of a wide range of fine chemicals in many fields, with a particular emphasis on their production from renewables.

Lower rim amide linked 8-amino quinoline and 8-amino naphthalene moiety 1,3,5-triderivatives of calix[6]arene L1 and L2 have been synthesized and characterized. While the L1 acts as a receptor molecule, the L2 acts as a control molecule. The complexation between L1 and Cu(2+) or Zn(2+) was delineated by the absorption and electrospray ionization (ESI) MS spectra. The binding ability of these molecules toward biologically important metal ions was studied by fluorescence and absorption spectroscopy. The derivative L1 detects Zn(2+) by bringing ratiometric change in the fluorescence signals at 390 and 490 nm, but in the case of Cu(2+), it is only the fluorescence quenching of 390 nm band that is observed, while no new band is observed at 390 nm. The stoichiometry of both the complexes is 1:1 and was confirmed in both the cases by measuring the ESI mass spectra. The isotopic peak pattern observed in the ESI MS confirmed the presence of Zn(2+) or Cu(2+) present in the corresponding complex formed with L1. Among these two ions, the Cu(2+) exhibits higher sensitivity. The density-functional theory (DFT) studies revealed the conformational changes in the arms and also revealed the coordination features in the case of the metal complexes. The arm conformational changes upon Zn(2+) binding were supported by nuclear Overhauser effect spectrometry (NOESY) studies. The stronger binding of Cu(2+) over that of Zn(2+) observed from the absorption study was further supported by the complexational energies computed from the computational data. While the L1 exhibited spherical particles, upon complexation with Cu(2+), it exhibits chain like morphological features in scanning electron microscopy (SEM) but only small aggregates in the case of Zn(2+). Thus, even the microscopy data can differentiate the complex formed between L1 and Cu(2+) from that formed with Zn(2+).

A sterically encumbered isopropyl group substituted fluorescent triphenylbenzene based azo-linked covalent organic polymer, iPrTAPB-Azo-COP, has been synthesized by Cu(I) catalysed homo coupling (amine-amine) reaction of 1,3,5-tris(4'-amino-3',5'-isopropylphenyl) benzene ((i)PrTAPB) under aerobic conditions. The Brunauer-Emmett-Teller (BET) and Langmuir surface areas of (i)PrTAPB-Azo-COP have been estimated to be 395 and 697 m(2) g(-1) with a pore diameter of 11.6 angstrom. Due to the presence of fluorescent triphenylbenzene platform (i)PrTAPB-Azo-COP exhibits broad emission band centred at 428 nm, when excited at 300 nm, as a result of extended conjugation. The inherent fluorescent nature of (i)PrTAPB-Azo-COP has been utilized for sensing electron-deficient polynitroaromatic compounds (PNACs) such as a picric acid (PA), dinitrotoluene (DNT), p-dinitrobenzene (p-DNB) and m-dinitrobenzene (m-DNB). Further, (i)PrTAPB-Azo-COP has also been utilized for capture of carbon dioxide as the azo-COP is enriched with CO2-philic nitrogen atoms apart from its microporosity. Since the azo (-N=N-) linkages are masked by the bulky isopropyl groups, (i)PrTAPB-Azo-COP exhibits a CO2 uptake of 6.5 and 19.4 wt% at 1 bar and 30 bar, respectively, at 273 K.

The structural behavior in aqueous mixtures of negatively charged silver nanoparticles (Ag NPs) together with the cationic surfactants cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium chloride (DTAC), respectively, has been investigated using SANS and SAXS. From our SANS data analysis we are able to conclude that the surfactants self-assemble into micellar clusters surrounding the Ag NPs. We are able to quantify our results by means of fitting experimental SANS data with a model based on cluster formation of micelles with very good agreement. Based on our experimental results, we propose a novel mechanism for the stabilization of negatively charged Ag NPs in a solution of positively charged surfactants in which cluster formation of micelles in the vicinity of the particles prevents the particles from aggregating. Complementary SAXS and DLS measurements further support this novel way of explaining stabilization of small hydrophilic nanoparticles in surfactant-containing solutions.

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A laccase/(2,2,6,6-tetramethylpiperidin-1-yl)oxy (TEMPO) mediated oxidation was combined with an aqueous, enantioselective copper-catalyzed Michael addition reaction of water in one pot. The copper catalyst was also immobilized onto DNA to induce enantioselectivity in the reaction. Low conversions were observed when the reactions were performed simultaneously, caused by an undesired reaction of an oxidised TEMPO intermediate. We increased the conversions by using a stepwise approach. Thus, after completion of the oxidation, the first reaction was stopped by inhibiting the enzyme with HCO2K and reducing the reactive TEMPO intermediate. Next, the Michael addition reaction was started by adding the Cu catalyst. By applying this strategy, an efficient two-step one-pot sequence, proceeding with 20% ee, was realized. The yield and ee of the second reaction were not affected by the oxidation reaction.

The syntheses of a new Schiff base, diethyl-5-(2-hydroxybenzylidene)aminoisophthalate (HL), and a copper complex, [Cu(L2)] (1), imparting L(-), have been described. Both the ligand HL and complex 1 have been thoroughly characterized by elemental analyses, electrospray ionization mass spectrometry, FT-IR, NMR ((1)H and (13)C), electronic absorption, and emission spectral studies and their structures determined by X-ray single-crystal analyses. Distinctive chemodosimetric behavior of HL and 1 toward Hg(2+) has been established by UV/vis, emission, and mass spectral studies. Comparative studies further revealed that the chemodosimetric response solely originates from selective hydrolysis of the aldimine moiety over the ester group and 1 exhibited greater selectivity toward Hg(2+) relative to HL while the sensitivity order is reversed. Further, these followed different hydrolytic pathways but ended up with the same product analyzed for diethyl-5-aminoisophthalate (DEA). Hg(2+)-induced displacement of Cu(2+) and subsequent hydrolysis of the -HC═N- moiety in 1 affirmed the identity of the actual species undergoing hydrolysis as HL. The occurrence of Cu(2+) displacement and Hg(2+) detection via hydrolytic transformation has been supported by various physicochemical studies.

International audience; High molecular weight terpolymers based on L-lactide (LLA), trimethylene carbonate (TMC) and glycolide (GA) are synthesized and characterized with the aim of assessing their potential in the development of bioresorbable cardiovascular stents. The effect of the composition on the thermal and mechanical properties of terpolymers is investigated in comparison with the corresponding PLLA-TMC copolymers as well as a PLLA homopolymer. Incorporation of GA units strongly decreases the crystallinity of PLLA-TMC-GA terpolymers due to its more random microstructure as evidenced by C-13 NMR. Meanwhile, the toughness is greatly improved, with only a slight loss of tensile strength. Plasma-treated poly[(L-lactide)-co-glycolide] (PLGA) fibers are used to reinforce the terpolymer matrix. Composite with 8 wt% fibers exhibits much higher tensile strength and modulus. A minitube is fabricated using a single-screw extruder, and a stent prototype is successfully manufactured from a terpolymer by a CNC engraving machine, thus showing the feasibility of the terpolymers for the development of bioresorbable cardiovascular stents. POLYM. ENG. SCI., 54:1418-1426, 2014. (c) 2013 Society of Plastics Engineers

Reaction of bulky 2,6-dibenzhydryl-4-methylaniline with 2-pyridinecaboxyaldehyde yielded [N,N] donor Schiff base, N-(2,6-dibenzhydryl-4-methylphenyl)-1-(pyridin-2-yl)methanimine (L-1). Reaction of L-1 with PdCl2 in toluene under reflux conditions afforded mononuclear complex, (LPdCl2)-Pd-1 (1). Complex 1 underwent salt metathesis with AgNO3 or NaN3 under ambient conditions to afford complexes, (LPdX2)-Pd-1 (X = NO3 (2), N-3 (3)). The new complexes were characterized by spectroscopic (IR, ESI-mass, NMR, UV-Vis), microanalytical (CHN) and thermal (TGA) techniques, in addition to a single crystal X-ray diffraction study for each of these compounds. Complexes 1-3 were employed in Suzuki coupling to evaluate their catalytic activity as well as the influence of coordinated anion on the course of catalysis. All the three complexes were found to be efficient catalysts in the coupling reactions involving aryl bromides with phenyl boronic acid while complex 3 was found to show the best activity. This is attributed to the thermal instability of azides and thus ease of decomposition of the terminal azido moiety under catalytic reaction conditions, facilitating the formation of L-Pd(0) species.

Atomic transfer radical polymerization (ATRP) of acrylamide has been accomplished in aqueous media at room temperature. By using methyl 2-chloropropionate (MeClPr) as the initiator and tris[2-(dimethylamino)ethyl]amine (Me6TREN)/copper halogenide (CuX) as the catalyst system, different linear polyacrylamides with apparent molecular weights up to >150 000 g/mol were synthesized with dispersities as low as 1.39. The molecular weights agreed well with the theoretical ones at relatively low-medium monomer/initiator ratios (

International audience; Synthesis of a new hybrid material (Pd/PPy) composed of polypyrrole globules with uniformly incorporated Pd nanoparticles via direct redox reaction between pyrrole and Pd(NH3)(4)Cl-2 in water has been recently reported (V.A. Zinovyeva, M.A.Vorotyntsev, I. Bezverkhyy, D. Chaumont, J.-C. Hierso, Adv. Funct. Mater. 21 (2011) 1064-1075). In the actual study, this procedure has been extended to synthesize a series of Pd/PPy powders with variable palladium content and morphological parameters. Depending on the monomer-to-oxidant ratio in reaction mixture, average diameters of Pd and PPy particles may change in the ranges of 1.25-1.45 and 27-62 nm, respectively, the Pd concentration being within 33.5-42.0 wt.%. In general terms, decrease of the monomer-to-oxidant ratio led to formation of the Pd/PPy hybrid material with smaller diameters of both components and a higher Pd loading. The Pd/PPy composites have been studied in Suzuki-Miyaura coupling and showed high catalytic efficiency. Aryl iodides, bromides and chlorides are active. The reaction can be performed using arylboronic acids or tetraarylborates, both in organic solvents and in water, thus making the process ecologically friendly. The recycling of the catalyst is possible if its particles are immobilized on the graphite support. The comparison of two samples revealed that Pd/PPy nanocomposite with the diameter of PPy spheres of about 30 nm is more efficient in catalysis, as compared to the sample with bigger PPy spheres (about 60 nm), due to transport limitations for reagents inside the polypyrrole sphere in the latter case. For palladium/polypyrrole nanocomposites with the small diameter of PPy sphere, which are easily penetrable for the reagents and in which all Pd nanoparticles are active. Pd content in polypyrrole spheres does not influence the yield of biaryls: the more is the Pd content in polypyrrole spheres, the less amount of catalyst is necessary to obtain the same yield of biaryl.

The P'CP'-pincer palladium complex-catalyzed allylation of N,N-dimethylsulfamoyl-protected aldimines with allyl(tributyl)stannane is investigated for the preparation of N-homoallylic sulfamides. The desired N,N-dimethylsulfamoyl-protected products are obtained in moderate to high yields in DMF under very mild conditions and a high yielding and convenient deprotection of the N,N-dimethylsulfamoyl group is also demonstrated. (C) 2009 Elsevier Ltd. All rights reserved.

DNA-bound copper(H) complexes serve as catalysts for the hydrolytic kinetic resolution of 2-pyridyloxiranes in water. Selectivity factors of up to 2.7 were achieved, indicating a chirality transfer of DNA to epoxides via a coordinated metal ion. (C) 2008 Elsevier Ltd. All rights reserved.

Diblock copolymers of poly(styrene-b-methacrylic acid) (PS-PMAA) of various compositions have been synthesized by anionic polymerization and were employed as templates for the development of "single-ion" polymer electrolyte systems. Lithium ions were introduced as the effective component that alters the phase state and contributes to ionic conductivity of these block polyelectrolytes. The local structure, microdomain morphology, and ion dynamics of the pure block copolymers and of the block polyelectrolytes were investigated by infrared spectroscopy, small-angle X-ray scattering, differential scanning calorimetry, and dielectric spectroscopy. Investigation of the microdomain structure revealed complexation of lithium ions with the carboxylate units of the PMAA phase in two types of coordination (chelating vs bringing) that alters the phase state of the copolymers and results in a change from the weak- to strong-segregation limit. The investigation of dynamics revealed a new dielectrically active process associated with a local relaxation of lithium ions coupled to the MAA segments via the two types of coordination. The ionic conductivity of the block polyelectrolytes was found enhanced by about 3 orders of magnitude relative to that of the parent copolymers. These results contribute to a better understanding of the changes in microdomain morphology as well as of the ion dynamics in systems resulting from the association of lithium ions with the charged PMAA block. Macromolecules

International audience; An attractive methodology based on diazonium chemistry has been developed for the surface modification of polymers such as polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS). The grafting procedure involves the in situ formation of diazoates in basic aqueous solution. The reactivity of calix[4]arene-tetradiazonium salts and a classical aryldiazonium salt was examined through comparative studies on gold and polymer surfaces. The surfaces were analyzed with a combination of techniques such as AFM, XPS, and ellipsometry. The results highlighted the fact that the calix[4]arene molecules are grafted as a robust and uniform monolayer both on gold and polymer surfaces, allowing a fine control over surface modification. Furthermore, the chemical postfunctionalization of the grafted calixarene platforms equipped with carboxylic-pendant groups was successfully performed with either an amine or an alcohol. These results open real possibilities in the controlled immobilization on polymers of a wide variety of molecules of interest such as biomolecules or chromophores and in the tailoring of polymer properties.

International audience; Self-assembly of a series of amphiphilic poly(oligo(ethylene glycol) methyl ether methacrylate)-block-poly(lactic acid)-block-poly(oligo(ethylene glycol) methyl ether methacrylate) (P(OEGMA)-b-PLLA-b-P(OEGMA)) copolymers was investigated. The copolymers were synthesized by a combination of ring-opening polymerization (ROP) of L-lactide and atom transfer radical polymerization (ATRP) of oligo ethylene glycol methyl ether methacrylate (OEGMA). The resulting brush-like triblock copolymers were characterized by H-1 NMR and size exclusion chromatography. Self-assembly behavior of the copolymers in deionized water was investigated by fluorescence spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The critical aggregation concentration ranged from 50 to 160 mg L-1 depending on the composition. The diameter of the nanoparticles (NPs) was determined by DLS and TEM. Images showed that these nano-sized objects displayed spherical and worm-like morphology with a length increasing with the hydrophilic content. Preliminary studies of drug loading and drug release with a water-insoluble model drug, namely curcumin, showed that these NPs are potential candidates for drug delivery carriers.

The synthesis of two A2B2 porphyrins, {5,15-bis-[4-(octyloxy)phenyl]-porphyrinato}zinc(II) (4) and {5,15-bis- (carbazol-3-yl-ethynyl)-10,20-bis-[4-(octyloxy)phenyl]-porphinato}-zinc(II) (9), is reported. Their photophysical properties were studied by steady-state absorption and emission. Substituting the carbazolylethynyl moieties at two of the meso positions results in a large bathochromic shift of all the absorption bands, a notable increase in the absorption coefficient of the Q(0,0) band, and higher fluorescence quantum yield compared to porphyrin 4, with two unsubstituted meso positions. Cyclic voltammetry and digital simulation show that electrogenerated radical ions of 9 are more stable than those of 4. The lack of substituents at the meso positions of 4 leads to dimerization reactions of the radical cation. Despite this, the annihilation reaction of 4 and 9 produces very similar electrogenerated chemiluminescence (ECL) intensity. Spectroelectrochemical experiments demonstrate that the electroreduction of 9 leads to a strong absorption band that might quench the ECL.

The synthesis and anion-recognition properties of the first halogen-bonding rotaxane host to sense anions in water is described. The rotaxane features a halogen-bonding axle component, which is stoppered with water-solubilizing permethylated beta-cyclodextrin motifs, and a luminescent tris(bipyridine) ruthenium (II)-based macrocycle component. H-1 NMR anion-binding titrations in D2O reveal the halogen-bonding rotaxane to bind iodide with high affinity and with selectively over the smaller halide anions and sulfate. The binding affinity trend was explained through molecular dynamics simulations and free-energy calculations. Photo-physical investigations demonstrate the ability of the interlocked halogen-bonding host to sense iodide in water, through enhancement of the macrocycle component's Ru-II metal-ligand charge transfer (MLCT) emission.

National audience; Double hydrophilic block copolymers (DHBC) consisting of a Jeffamine block, a statistical copolymer based on ethylene oxide and propylene oxide units possessing a lower critical solution temperature (LCST) of 30 degrees C in water, and Poly(L-glutamic acid) as a pH-responsive block were synthesized by ring-opening polymerization of gamma-benzyl-L-glutamate N-carboxyanhydride using an amino-terminated Jeffamine macroinitiator, followed by hydrolysis. This DHBC proved thermoresponsive as evidenced by dynamic light scattering and small-angle neutron scattering experiments. Spherical micelles with a Jeffamine core and a poly(L-glutamic acid) corona were formed above the LCST of Jeffamine. The size. of the core of such micelles decreased with increasing temperature, with complete core dehydration being achieved at 66 degrees C. Such behavior, commonly observed for thermosensitive homopolymers forming mesoglobules, is thus demonstrated here for a DHBC that self-assembles to generate thermoresponsive micelles of high colloidal stability.

Barbier-type Zn and In-mediated allylations of an N,N-(dimethylsulfamoyl)-protected aldimine with different allyl bromides were investigated for the preparation of N-homoallylic sulfamides. The desired N,N-(dimethylsulfamoyl)-protected products were obtained in moderate to high yields in THF as the optimal solvent. Their further derivatization was demonstrated by a facile preparation of a functionalized dehydropiperidine by an allylation/olefin metathesis reaction sequence. A high yielding deprotection of the N,N-dimethylsulfamoyl group was likewise demonstrated. (c) 2007 Elsevier Ltd. All rights reserved.

Mixed polymeric micelles have been prepared from aqueous solutions of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(glyceryl methacrylate), PDMAEMA45-b-PGMA90, and poly(acrylic acid)-block-poly(acrylamide), PAA42-b-PAAm417, through complex coacervation of the oppositely charged blocks. Rather monodisperse, spherical aggregates are formed with a Rh = 15.2 ± 0.4 nm. The extent of chain mixing between poly(acrylic acid) and poly(2-(dimethylamino)ethyl methacrylate) in the micellar core and poly(acrylamide) and poly(glyceryl methacrylate) in the micellar corona has been investigated by 2D 1H NMR NOESY experiments. The presence of cross-peaks for protons in different core and corona blocks indicates that the two blocks are in close proximity (

The rhodium-phosphoramidite-catalyzed asymmetric conjugate addition of arylboronic acids to enones proceeds at room temperature using [Rh(OH)(cod)](2) or [RhCl(cod)](2)/KOH as stable and readily available catalyst precursors. (c) 2005 Published by Elsevier Ltd.

A quartz trap for on-line preconcentration of Cd species was designed. The cold vapour generation technique was used for the generation of Cd species. The trapping medium was formed by external heating of the inlet arm of a quartz T-tube. The generated analyte species were trapped on a quartz surface heated to the collection temperature, 350 degreesC, and the collected species were revolatilized when the trap was heated further to revolatilization temperature, 1000 degreesC, and hydrogen gas was introduced in the trapping medium. Two-level fractional factorial design and central composite design were used to optimize generation conditions in the flow injection mode. The results of the fractional factorial design demonstrated that the factors and their interactions were statistically significant. Three factors, length of reaction coil, carrier HCl concentration and NaBH4 concentration, were considered to be the most significant parameters in the optimization and their optimum values were found to be 30 cm, 0.3 M and 3% (m/v), respectively. Sea-water (BCR), tomato leaves (NIST 1573a) and oyster tissue ( NIST 1566b) standard reference materials were analyzed to assess the accuracy of the proposed method. For a collection period of 3.0 min, i.e., 6.0 ml sample volume, the 3sigma limit of detection was 1.8 pg ml(-1); the enhancement factor for LOD was found to be 90 as compared with FI-HGAAS. The sample throughput rate was 12 h(-1).

The meso-salicylaldehyde substituted BODIPY was synthesized over a sequence of steps and characterized by X-ray crystallography, mass, NMR, absorption, fluorescence and electrochemical techniques. The crystal structure showed the presence of strong intramolecular hydrogen bonding between hydroxyl and formyl groups, which induces rigidity in the BODIPY core and makes the BODIPY relatively more fluorescent than the meso-phenyl BODIPY. Our studies showed that the meso-salicylaldehyde BODIPY can be used as a specific chemidosimetric sensor for CN(-) ions. The presence of a hydroxyl group adjacent to a formyl group helps in activating the formyl group for a nucleophilic attack. Upon addition of the CN(-) ion to the meso-salicylaldehyde BODIPY, the CN(-) ion attacks the formyl group and converts it to the cyanohydrin group. This irreversible reaction was monitored by following the changes in absorption, fluorescence and electrochemical properties and the results support the view that the meso-salicylaldehyde substituted BODIPY can be used as a specific chemodosimetric sensor for CN(-) ions. To substantiate the role of the hydroxyl group, we also prepared the meso(m-formylphenyl) BODIPY which contains only the formyl group on meso-phenyl, and our studies indicated that the meso(m-formylphenyl) BODIPY cannot be used as a chemodosimetric sensor for CN(-) ions, as verified by absorption and emission studies.

Detailed herein is the use of 2,3,9,10,16,17,23,24-octatosylaminophthalocyanine as a chromogenic chemosensor for anions. The host:guest complexes formed during the sensing event can be regenerated by acid treatment without loss of the sensing ability. This allows the phthalocyanine chemosensor to be reused. This system also responds in a colorimetric manner when exposed to the neutral solvent molecules, dimethyl sulfoxide and methanol. A single-crystal X-ray structure of the Pc 1:2 MeOH complex was obtained. It illustrates the main interactions between the host:guest species in the solid state. Fits of the binding curves are consistent with this stoichiometry predominating in the solution state. (C) 2014 Elsevier B.V. All rights reserved.

A laccase/(2,2,6,6-tetramethylpiperidin-1-yl)oxy (TEMPO) mediated oxidation was combined with an aqueous, enantioselective copper-catalyzed Michael addition reaction of water in one pot. The copper catalyst was also immobilized onto DNA to induce enantioselectivity in the reaction. Low conversions were observed when the reactions were performed simultaneously, caused by an undesired reaction of an oxidised TEMPO intermediate. We increased the conversions by using a stepwise approach. Thus, after completion of the oxidation, the first reaction was stopped by inhibiting the enzyme with HCO2K and reducing the reactive TEMPO intermediate. Next, the Michael addition reaction was started by adding the Cu catalyst. By applying this strategy, an efficient two-step one-pot sequence, proceeding with 20% ee, was realized. The yield and ee of the second reaction were not affected by the oxidation reaction.

International audience; Green rusts (GRs) are mixed Fe(II)-Fe(III) hydroxides with a high reactivity toward organic and inorganic pollutants. GRs can be produced from ferric reducing or ferrous oxidizing bacterial activities. In this study, we investigated the capability of Klebsiella mobilis to produce iron minerals in the presence of nitrate and ferrous iron. This bacterium is well-known to reduce nitrate using an organic carbon source as electron donor but is unable to enzymatically oxidize Fe(II) species. During incubation, GR formation occurred as a secondary iron mineral precipitating on cell surfaces, resulting from Fe(II) oxidation by nitrite produced via bacterial respiration of nitrate. For the first time, we demonstrate GR formation by indirect microbial oxidation of Fe(II) (i.e., a combination of biotic/abiotic processes). These results therefore suggest that nitrate-reducing bacteria can potentially contribute to the formation of GR in natural environments. In addition, the chemical reduction of nitrite to ammonium by GR is observed, which gradually turns the GR into the end-product goethite. The nitrogen mass-balance clearly demonstrates that the total amount of ammonium produced corresponds to the quantity of bioreduced nitrate. These findings demonstrate how the activity of nitrate-reducing bacteria in ferrous environments may provide a direct link between the biogeochemical cycles of nitrogen and iron.

The influence of morphology on the hydrolytic degradation behavior of poly(L-lactide) has been studied. High molecular weight and highly crystalline as-polymerized poly(L-lactide) was obtained in high yields through melt polymerization. Poly(L-lactide) fiber with a draw ratio of 5.6 was obtained by hot-drawing solution-spun fiber. During the bulk degradation of as-polymerized poly(L-lactide), a rapid decrease of molecular weight and tensile properties was observed. This could be explained by the morphology of the material and the presence of thermal stresses and subsequent generation of microcracks. The lamellar crystallites in as-polymerized poly(L-lactide) appeared to be very stable towards hydrolysis. The resorption time of high molecular weight as-polymerized poly(L-lactide) in vivo was estimated at 40-50 yr by extrapolation of molecular weight data. Hot-drawn poly(L-lactide) fiber showed exceptional hydrolytic stability under a static load and substantially retained its mechanical properties over a period of more than 5 yr. The high perfection of the crystalline fiber and the elimination of micro-voids obtained by hot-drawing prevented penetration of water and induced surface erosion of the fiber.

Blends of D,L-lactide/glycolide copolymers were synthesized and their properties and in vitro degradation behaviour were evaluated as a function of chain architecture and blend composition. Tensile and impact properties of the blends are hardly influenced by matrix composition and chain architecture, but predominantly vary with the amount of rubber. In vitro degradation showed that hydrolytic degradation is enhanced by the incorporation of glycolide into the poly(D,L-lactide) matrix. Surprisingly, blends based on 6-arm star-shaped poly(D,L-lactide-co-glycolide) retain their mechanical properties for a longer period than blends with linear matrices of comparable composition. Physical aging of the linear copolymers is more severe and faster than that of star-shaped copolymers. (C) 1997 Elsevier Science Ltd.

A new bipyridyl derivative 1 bearing rhodamine B as visible fluorophore was designed, synthesized and characterized as a fluorescent and colorimetric sensor for metal ions. Interaction with Cu2+, Zn2+, Cd2+, Hg+, and Hg2+ ions was followed by UV/Vis and emission spectroscopy. Upon addition of these metal ions, different colorimetric and fluorescent responses were observed. “Off‐on‐off” (Cu2+, Zn2+, and Hg2+) and “off‐on” (Hg+ and Cd2+) systems were obtained. Probe 1 was explored to mimic XOR and OR logic operations for the simultaneous detection of Hg+–Cu2+ and Hg+–Zn2+ pairs, respectively. DFT calculations were also performed to gain insight into the lowest‐energy gas‐phase conformation of free receptor 1 as well as the atomistic details of the coordination modes of the various metal ions. S.M.S., E.O., and H.M.S. thank the FCT‐MCTES (Portugal) for their postdoctoral grants SFRH/BPD/64752/2009, SFRH/BPD/72557/2010 and SRFH/BPD/73997/2010, respectively. The authors thank the Scientific Association PROTEOMASS (Portugal) for financial support. C.N. thanks the Xunta de Galicia (Spain) for her postdoctoral contract (I2C program). C.L. and J.L.C. thank REQUIMTE‐FCT PEst‐C/EQB/LA0006/2013 for funding, and the NMR service from the National NMR Facility, supported by Fundação para a Ciência e a Tecnologia (RECI/BBB‐BQB/0230/2012) SI

Boron-dipyrromethenes containing dithioacetal substituents at 3,5-positions, 3,5-bis(dithioacetal) BODIPYs 1 and 2, were synthesized by treating their corresponding 3,5-diformyl BODIPYs 3 and 4 with excess methyl thioglycolate under mild acid catalyzed reaction conditions. The spectral and electrochemical studies indicated that 3,5-bis(dithioacetal) BODIPYs are less electron deficient compared to 3,5-diformyl BODIPYs. Furthermore, dithioacetal functional groups are very useful for binding metal ions and our studies clearly showed that these dyes can act as selective chemodosimetric probes for the recognition of Hg(II) ions over various other metal ions. The sensing phenomenon employs unique and irreversible Hg(II) promoted deprotection of the dithioacetal groups to aldehyde groups which is clearly demonstrated by absorption, fluorescence, HR-MS and NMR studies. Competitive binding experiments demonstrate that BODIPY 1 can specifically detect Hg(II) ions even in the presence of various other metal ions.

[RuCl(η5-3-phenylindenyl)(PPh3)2] (1) has been shown to be a highly active catalyst for the isomerisation of allylic alcohols to the corresponding ketones. A variety of substrates undergo the transformation, typically with 0.25-0.5 mol% of catalyst at room temperature, outperforming commonly-used complexes such as [RuCl(Cp)(PPh3) 2] and [RuCl(η5-indenyl)(PPh3) 2]. Mechanistic experiments and density functional theory have been employed to investigate the mechanism and understand the effect of catalyst structure on reactivity. These investigations suggest a oxo-π-allyl mechanism is in operation, avoiding intermediate ruthenium hydride complexes and leading to a characteristic 1,3-deuterium shift. Important mechanistic insights from DFT and experiments also allowed for the design of a protocol that expands the scope of the transformation to include primary allylic alcohols We thank the ERC (Advanced Investigator Award ` FUNCAT' to SPN) and the EPSRC for funding. Umicore is thanked for gi. s of materials. SPN is a Royal Society Wolfson Merit Award holder. Melanja Smith and Dr Tomas Lebl are thanked for assistance with NMR spectroscopy facilities. Dr Cesar A. Urbina-Blanco is acknowledged for useful discussions. LC thanks the HPC team of Enea for using the ENEA-GRID and the HPC facilities CRESCO in Portici (Italy) for access to remarkable computational resources. AP thanks the Spanish MICINN for a Ramon y Cajal contract (RYC-2009-05226) and European Commission for a Career Integration Grant (CIG09-GA-2011-293900)

Polymers 5(4), 1229-1240 (2013). doi:10.3390/polym5041229, Published by Molecular Diversity Preservation International, Basel