François Delattre

Programmable Polymer‐Based Supramolecular Temperature Sensor with a Memory Function

A new class of polymeric thermometers with a memory function is reported that is based on the supramolecular host-guest interactions of poly(N-isopropylacrylamide) (PNIPAM) with side-chain naphthalene guest moieties and the tetracationic macrocycle cyclobis(paraquat-p-phenylene) (CBPQT(4+)) as the host. This supramolecular thermometer exhibits a memory function for the thermal history of the solution, which arises from the large hysteresis of the thermoresponsive LCST phase transition (LCST = lower critical solution temperature). This hysteresis is based on the formation of a metastable soluble state that consists of the PNIPAM-CBPQT(4+) host-guest complex. When heated above the transition temperature, the polymer collapses, and the host-guest interactions are disrupted, making the polymer more hydrophobic and less soluble in water. Aside from providing fundamental insights into the kinetic control of supramolecular assemblies, the developed thermometer with a memory function might find use in applications spanning the physical and biological sciences.

Fluorescent Indolizine-β-Cyclodextrin Derivatives for the Detection of Volatile Organic Compounds

This paper presents the synthesis, the structural determination and the sensing capabilities toward Volatile Organic Compounds (VOCs) of a new class of fluorescent indolizine-cyclodextrin sensors. Two different pathways, both involving bipyridinium ylides and 6-amino-b-cyclodextrin, have been used to carry out the synthesis of these sensors. The macrocycle structures were dominantly established by 1H-NMR spectra and systematically studied by molecular modelling (MM3, AM1, AM1-COSMO methods). The sensing capabilities of the sensors were evaluated by emission of fluorescence, during the inclusion of the guest (adamantanol or aromatic derivatives) into the cyclodextrin (CD) host cavity. The host/guest complex formation was investigated by formation constant determinations, using experimental methods, coupled with theoretical calculations of formation energies using a specific docking procedure. Both experimental and theoretical results suggest that some compounds would make very attractive sensors for VOC detection. Some compounds could also be taken into consideration as biological markers.

Structure and reactivity of cycloimmonium ylides. Theoretical study in triazolium ylides by AM1, PM3 and DFT procedure methods

Abstract This paper reports some general remarks on structure and reactivity of monosubstituted and disubstituted cycloimmonium ylides. The results have been achieved by calculations on ylide bond lengths, bond orders, dipolar moments and rotational barriers. Some aspects have been followed on charges and high-occupied molecular orbital coefficients of ylide carbon atoms during rotation around ylide bond. The AM1, PM3 and DFT procedure methods have been used in this study. Three ylidic systems have been selected as models of cycloimmonium ylides: (a) 1-ethoxycarbonylmethyl 1,2,4-triazol-1-ium 4′-nitrobenzoyl 2″,4″,6″-trinitrophenyl methylides, (b) 4-phenylbenzoyl 1,2,4-triazol-1-ium methylide and (c) 4-phenyl dibenzoyl 1,2,4-triazol-1-ium methylide. DFT and AM1 procedure methods are appropriate for the description of monosubstituted cycloimmonium ylides. Only DFT procedure method is recommended for the description of the non-planar disubstituted cycloimmonium ylides. The resonance interaction in planar monosubstituted and planar disubstituted cycloimmonium ylide systems permits to carry out 3+2 cycloadditions preferably in non or less polar solvents.

Efficient synthesis of a fluorescent tripod detection system for pesticides by microwave-assisted click chemistry.

A new tripod molecule containing an aromatic core bearing three peracetylated cyclodextrins was synthesized via a microwave-assisted Huisgen 1,3-dipolar cycloaddition and was studied by fluorescence spectroscopy. The photoluminescent properties of complexation phenomena with different pesticides were evaluated in acetonitrile. Fluorescence titrations have been performed to calculate binding constants, sensitivity factors, and limit of detection of the resulting complexes. 2D NMR experiments confirmed the inclusion of pesticide in the hydrophobic cavity of the macrocycle and validated the supramolecular association responsible for the quenching of the fluorescence.

Monitoring survey of the use patterns and pesticide residues on vegetables in the Niayes zone, Senegal

The main objective of this work was to determine the impact of pesticide use practices on vegetables contamination in the Niayes zone of Dakar. A preliminary survey involving 200 farmers, showed the application of pesticides belonging to different groups on vegetable crops. Use practices in terms of application intervals and methods, measuring tools and dosage were not in compliance with good agricultural practices. In view of survey results, investigations on vegetable contamination were conducted. Therefore, 175 vegetable samples including cabbage (31 samples), lettuce (88 samples), tomato (57 samples) collected from four sites of the Niayes zone during four campaigns, were analyzed for residues of 21 pesticides, eighteen of which (18) were cited to be used by farmers. The results indicated that 65% of tomato samples, 71% of lettuce and 93% of cabbage contained one or more detectable residues. Among the monitored pesticides dicofol, chlorpyrifos, DDTs, dimethoate, and λ-cyhalothrin were the most predominant, found in at least 35% of samples for each vegetable. The frequencies of pesticide detection were, generally in agreement with the citation frequencies. The results provided important information on vegetable contamination status and pointed an urgent need to control pesticide use.

Synthesis, binding and self-assembly properties of a well-defined pillar[5]arene end functionalised polydimethylacrylamide

The synthesis, binding and self-assembly properties of a well-defined pillar[5]arene end-functionalised poly(dimethylacrylamide)(MePilla-PDMAC) are reported. In order to synthesise MePilla-PDMAC, a new trithiocarbonate type RAFT agent MePilla-CTA was developed incorporting a partially methylated pillar[5]arene moiety. Kinetic studies clearly indicated the propensity of MePilla-CTA to control the polymerisation of DMAC. Interestingly, as PDMAC type chains display good solubilty both in organic and aqueous media, MePilla-PDMAC was able of specifically bind electron deficient guest molecules at the α-chain-end both in chloroform and water. Complex formation was found to be reversible upon addition of chloride anions or heating in organic and aqueous media, respectively. Furthermore, cryo-TEM, VT-NMR (1H) and VT-DLS investigations also indicated the ability of MePilla-PDMAC to self-assemble into micelle-like aggregates in water showing reversible recognition properties.

SYNTHESIS OF NEW FLUORESCENT β-CYCLODEXTRIN SENSOR

The synthesis of a new fluorescent sensor incorporating a fluoro pyridine indolizinic unit and a ßcyclodextrin fragment by two different synthetic ways is described.

Recognition of iron ions by carbazole–desferrioxamine fluorescent sensor and its application in total iron detection in airbone particulate matter

This work reports on an efficient microwave irradiation synthesis of a new fluorescent chemosensor based on desferrioxamine B (DFO-B) and carbazole moiety. Furthermore, this novel chemosensor was employed for a comparative study of real environmental samples of airbone particulate matter collected from Dunkirk (Northern of France). Among selected relevant metal cations present in its airbone particulate matter, such as Na(+), K(+), Mg(2+), Ca(2+), Al(3+), Cr(3+), Mn(2+) and Zn(2+), this molecular device proved to be outstandingly sensitive toward Fe(3+) with a limit of detection of 1.49 ppb (2.1×10(-8) M) in methanol allowing the estimation of total iron in atmospheric particles.

Ultrasound-promoted tosylation of oligo(ethylene glycols)

A series of oligo(ethylene glycols) was efficiently tosylated by ultrasound procedure within dichloromethane in the presence of triethylamine. Results show that sonochemical synthesis of oligo(ethylene glycol) ditosylates has a double advantage since it does not use catalysts and it drastically reduces the reaction time. This straightforward method represents an eco-friendly alternative to the traditional tosylation by pyridine synthesis.