Cooperative Anion-π and C-H-Cl Interactions in Multifunctional Naphthalene-Based Receptors for Chloride Recognition: Cage-size Modulation Through Substitution Patterns.

This article focuses on developing selective receptors for chloride. A series of novel receptors based on a rigid naphthalene spacer bearing tetrafluoropyridines (TFPs) in various substitution patterns has been designed and synthsized. The topology of the receptors was confirmed by X-ray cristallography. Their complexation efficiency was essentially studied in the gas phase through mass spectrometry experiments. Density Functional Theory (DFT) calculations and NMR titration were also performed.

Chloride Binding Modulated by Anion Receptors Bearing Tetrazine and Urea.

Modulation and fine-tuning of the strength of weak interactions to bind anions are described in a series of synthetic receptors. The general design of the receptors includes both a urea motif and a tetrazine motif. The synthetic sequence towards three receptors is detailed. Impacts of H-bond strength and linker length between urea and tetrazine on chloride complexation are studied. Binding properties of the chloride anion are examined in both the ground and excited states using a panel of analytical methods (NMR spectroscopy, mass spectrometry, UV/Visible spectroscopies, and fluorescence). A ranking of the receptors by complexation strength has been determined, allowing a better understanding of the structure-properties relationship on these compounds.

Labeled TEMPO-Oxidized Mannan Differentiates Binding Profiles within the Collectin Families.

Establishing the rapid and accurate diagnosis of sepsis is a key component to the improvement of clinical outcomes. The ability of analytical platforms to rapidly detect pathogen-associated molecular patterns (PAMP) in blood could provide a powerful host-independent biomarker of sepsis. A novel concept was investigated based on the idea that a pre-bound and fluorescent ligand could be released from lectins in contact with high-affinity ligands (such as PAMPs). To create fluorescent ligands with precise avidity, the kinetically followed TEMPO oxidation of yeast mannan and carbodiimide coupling were used. The chemical modifications led to decreases in avidity between mannan and human collectins, such as the mannan-binding lectin (MBL) and human surfactant protein D (SP-D), but not in porcine SP-D. Despite this effect, these fluorescent derivatives were captured by human lectins using highly concentrated solutions. The resulting fluorescent beads were exposed to different solutions, and the results showed that displacements occur in contact with higher affinity ligands, proving that two-stage competition processes can occur in collectin carbohydrate recognition mechanisms. Moreover, the fluorescence loss depends on the discrepancy between the respective avidities of the recognized ligand and the fluorescent mannan. Chemically modulated fluorescent ligands associated with a diversity of collectins may lead to the creation of diagnostic tools suitable for multiplex array assays and the identification of high-avidity ligands.

A bioinspired approach to fabricate fluorescent nanotubes with strong water adhesion by soft template electropolymerization and post-grafting.

HYPOTHESIS: In this original work, we aim to control both the surface wetting and fluorescence properties of extremely ordered and porous conducting polymer nanotubes prepared by soft template electropolymerization and post-grafting. For reaching this aim, various substituents of different hydrophobicity and fluorescence were post-grafted and the post-grafting yields were evaluated by surface analyses. We show that the used polymer is already fluorescent before post-grafting while the post-grafting yield and as a consequence the surface hydrophobicity highly depend on the substituent. EXPERIMENTS: Here, we have chosen to chemically grafting various fluorinated and aromatic substituents using a post-grafting in order to keep the same surface topography. Flat conducting polymer surfaces with similar properties have been also prepared for determining the surface energy with the Owens-Wendt equation and estimating the post-grafting yield by X-ray Photoemission Spectroscopy (XPS) and Time of Flight Secondary Emission Spectrometry (ToF-SIMS). For example, using fluorinated chains of various length (C4F9, C6F13 and C8F17), it is demonstrated that the surface hydrophobicity and oleophobicity do not increase with the fluorinated chain length due to the different post-grafting yields and because of the presence of nanoroughness after post-grafting. FINDINGS: These surfaces have high apparent water contact angle up to 130.5° but also strong water adhesion, comparable to rose petal effect even if there are no nanotubes on petal surface. XPS and ToF-SIMS analyses provided a detailed characterisation of the surface chemistry with a qualitative classification of the grafted surfaces (F6 > F4 > F8). SEM analysis shows that grafting does not alter the surface morphology. Finally, fluorescence analyses show that the polymer surfaces before post-treatment are already nicely fluorescent. Although the main goal of this paper was and is to understand the role of surface chemistry in tailoring the wetting properties of these surfaces rather than provide specific application examples, we believe that the obtained results can help the development of specific nanostructured materials for potential applications in liquid transport, or in stimuli responsive antimicrobial surfaces.

Application of pyridine-modified chitosan derivative for simultaneous adsorption of Cu(II) and oxyanions of Cr(VI) from aqueous solution.

The bioadsorbent C1, which is a chitosan derivative prepared in a one-step synthesis, was successfully used to adsorb Cr(VI) and Cu(II) simultaneously. Here, for the first time the simultaneous adsorption of a cation and an anion was modeled using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. Batch studies of the adsorption of Cu(II) and Cr(VI) in single and binary aqueous solutions were performed as a function of initial solute concentration, contact time, and solution pH. The maximum adsorption capacities of C1 in single and binary aqueous solutions were 1.84 and 1.13 mmol g-1 for Cu(II) and 3.86 and 0.98 mmol g-1 for Cr(VI), respectively. The reuse of C1 was investigated, with Cu(II) ions being almost completely desorbed and fully re-adsorbed. For Cr(VI), the desorption was incomplete resulting in a lower re-adsorption. Energy-dispersive X-ray spectroscopy was used for mapping the distributions of Cr(VI) and Cu(II) adsorbed on the C1 surface in single and binary adsorption systems. Isothermal titration calorimetry experiments were performed for Cr(VI) and Cu(II) adsorption in single solutions. The thermodynamic parameters of adsorption showed that the adsorption of both metal ions was enthalpically driven, but entropically unfavorable.

Design and property investigation on a five-interaction-based fluorescent anion receptor clip.

A molecular clip combining a doubly substituted fluorescent anion-π donor probe and two flexible arms bearing H-bond motifs constitutes a new generation of anion receptors. Five simultaneous non-covalent interactions are highlighted by theoretical complexation studies with five different anions. A large range of analytical techniques (electrospray-tandem mass spectrometry, NMR, UV-visible, steady-state and time-resolved fluorescence) were deployed to evaluate the stoichiometry and association constants with the selected anions. The photophysical and anion-π donor properties of the tetrazine ring allowed fine characterization of the binding properties of the ligand. Based on previously published results, an anti-cooperativity effect in non-covalent interactions was demonstrated.

Fluorescein Derivatives as Fluorescent Probes for pH Monitoring along Recent Biological Applications.

Potential of hydrogen (pH) is one of the most relevant parameters characterizing aqueous solutions. In biology, pH is intrinsically linked to cellular life since all metabolic pathways are implicated into ionic flows. In that way, determination of local pH offers a unique and major opportunity to increase our understanding of biological systems. Whereas the most common technique to obtain these data in analytical chemistry is to directly measure potential between two electrodes, in biological systems, this information has to be recovered in-situ without any physical interaction. Based on their non-invasive optical properties, fluorescent pH-sensitive probe are pertinent tools to develop. One of the most notorious pH-sensitive probes is fluorescein. In addition to excellent photophysical properties, this fluorophore presents a pH-sensitivity around neutral and physiologic domains. This review intends to shed new light on the recent use of fluorescein as pH-sensitive probes for biological applications, including targeted probes for specific imaging, flexible monitoring of bacterial growth, and biomedical applications.

Synthesis, crystal structure at 219†K and Hirshfeld surface analyses of 1,4,6-tri-methyl-quinoxaline-2,3(1H,4H)-dione monohydrate.

The asymmetric unit of the title compound, C11H12N2O2·H2O, contains a mol-ecule of 1,4,6-trimethyl-1,4-di-hydro-quinoxaline-2,3-dione and a solvent water mol-ecule. Four atoms of the benzene ring are disordered over two sets of sites in a 0.706 (7):0.294 (7) ratio while the N-bound methyl groups are rotationally disordered with occupancy ratios of 0.78 (4):0.22 (4) and 0.76 (5):0.24 (5). In the crystal, mol-ecules are linked by O-H⋯O and C-H⋯O hydrogen bonds into layers lying parallel to (10). The Hirshfeld surface analysis indicates that the most important contributions to the packing arrangement are due to H⋯H (51.3%) and O⋯H/H⋯O (28.6%) inter-actions. The mol-ecular structure calculated by density functional theory is compared with the experimentally determined mol-ecular structure, and the HOMO-LUMO energy gap has been calculated.

Synthesis, crystal structures and Hirshfeld surface analysis of 1,4-dibenzyl-6-methyl-1,4-di-hydro-quinoxaline-2,3-dione.

The title quinoxaline mol-ecule, C23H20N2O2, is not planar, the dihedral angle angle between the mean planes of the benzene rings being 72.54 (15)°. In the crystal, mol-ecules are connected into chains extending parallel to (10) by weak C-H⋯O hydrogen bonds. Weak C-H⋯π inter-actions link the chains, forming a three-dimensional network structure. Hirshfeld surface analysis revealed that the most important contributions for the crystal packing are from H⋯H (48.7%), H⋯C/C⋯H (32.0%), H⋯O/O⋯H (15.4%), C⋯C (1.9%), H⋯N/N⋯H (1.1%) contacts.

Intertwined Detection and Recognition Roles of Tetrazine in Synergistic Anion-π and H-bond Based Anion Receptor.

The intrinsic properties of tetrazine as a π-anion receptor and as an on/off recognition probe merged with H-bond ability of an urea motif into a single architecture constitutes a new generation of well-defined anion receptors. Complexation properties directly benefit from the dual and synergistic contribution of tetrazine and urea. In this study, we report on the synthesis and assessment of binding properties to anions of diverse geometries. Association constants have been predicted by theoretical calculations and evaluated by multiple and complementary experimental techniques including electrospray-mass tandem spectroscopy, NMR, UV-visible, steady state fluorescence spectroscopies and time resolved fluorescence. These results provide the basis for a better understanding of both the complexation and the anion-dependent quenching mechanism.

Aminated cellulose as a versatile adsorbent for batch removal of As(V) and Cu(II) from mono- and multicomponent aqueous solutions.

A bioadsorbent (CEDA) capable of adsorbing As(V) and Cu(II) simultaneously was prepared by tosylation of microcrystalline cellulose (MC) and nucleophilic substitution of the tosyl group by ethylenediamine. MC, tosyl cellulose, and CEDA were characterized by elemental C, H, N, and S analysis, infrared spectroscopy, and 13C solid-state nuclear magnetic resonance spectroscopy. The adsorption of As(V) and Cu(II) on CEDA was evaluated as a function of solution pH, contact time, and initial solute concentration. The maximum adsorption capacities of CEDA for As(V) and Cu(II) were 1.62 and 1.09 mmol g-1, respectively. The interactions of As(V) and Cu(II) with CEDA were elucidated using thermodynamic parameters, molecular quantum mechanics calculations, and experiments with ion exchange of Cd(II) by Cu(II), and As(V) by SO42-. Adsorption enthalpies were determined as a function of surface coverage of the CEDA, using isothermal titration calorimetry, with ΔadsH° values of -32.24 ± 0.07 and -93 ± 2 kJ mol-1 obtained for As(V) and Cu(II), respectively. The potential to reuse CEDA was evaluated and the interference of other ions in the adsorption of As(V) and Cu(II) was investigated. Multi-component experiments showed that Cd(II), Co(II), Ni(II), and Pb(II) did not interfere in the adsorption of Cu(II), while SO42- inhibited As(V) adsorption.

Helically shaped cation receptor: design, synthesis, characterisation and first application to ion transport.

The methyl ester of 8-oxo-8H-indeno[2',1':7,8]naphtho[1,2-b]thiophene-2-carboxylic acid (1) and its corresponding PEGylated ester were synthesised and fully characterised. X-ray diffraction studies on (1) confirmed the helical structure of the receptor and that it is self-assembled into layers by π-π interactions. An in-depth study by DFT calculations and MS experiments (ESI-MS, MS/MS, IMRPD and ESI-IMS-MS) was carried out between (1) and the physiological cation K+. The formation of supramolecular complexes between (1) and K+ with different stoichiometries was demonstrated and the cation K+ preferentially interacts with the oxygen atoms of the carbonyl bond of the ketone and ester groups and the sulphur atom of the heterocycle. The ability of the two synthesized aromatic architectures to transport ions across a model lipid membrane has been studied by electrophysiology experiments. The formation of pores was observed, even at nanomolar concentrations. Since the PEGylated molecule showed more regular pore definitions than the hydrophobic molecule, the introduction of a polar hydrophilic chain made it possible to control the orientation of the aromatic architectures within the membrane.

Experimental Characterization of Droplet Adhesion: The Ejection Test Method (ETM) Applied to Surfaces with Various Hydrophobicity.

We study the wetting and the adhesive behavior of substrates made by electropolymerization of copolymers of pyrene substituted with fluoroalkyl and adamantyl groups. The hydrophobicity and water adhesion properties can be tuned by the molar percentage (mol %) of each pyrene monomer so that the substrate properties can vary from superhydrophobic to parahydrophobic, with respectively low and high water adhesion. The ejection test method (ETM) is proposed as an original tool to discriminate and characterize such substrates. Using a catapult-like apparatus, a droplet initially at rest on the surface is subject to a large acceleration and is subsequently ejected. Depending on the surface properties and initial catapult acceleration, the ejection is more or less efficient and occurs with or without fragmentation of the droplet. The ETM is shown to be a complementary test to the lateral adhesion and hysteresis classical measurements. This work is of importance for the understanding of adhesion phenomena on various surfaces and for a better quantitative characterization of their adhesive properties.

Topology and Electronic Density Driven Generation of Alkali Cation Complexes.

The formation and characterization of K+ and Cs+ complexes originating from the cooperativity of three non-covalent interactions is explored. The tridimensional preorganization of the naphthothiophene platform displays a favorable well-defined bay region combining a π fragment and a carbonyl moiety flanking a central sulfur atom. A joint theoretical and experimental infrared multiple photon dissociation (IRMPD) study allowed deciphering the key contribution of the orthogonal phenyl fragment to the elaboration of alkali metal complexes. In combination with S and CO interactions, the π-cation interaction significantly enhances the binding energies of naphthothiophene derivatives.

Synthesis, characterisation and application of pyridine-modified chitosan derivatives for the first non-racemic Cu-catalysed Henry reaction.

The preparation, characterisation and application of two pyridine-modified chitosan derivatives (C1 and C2) containing Cu(OAc)2 adsorbed as catalysts for the conversion of benzaldehyde into 2-nitro-1-phenylethanol are described. Quantitative solid-state 13C multiple-contact cross-polarization, magic-angle-spinning, nuclear magnetic resonance (MC-CP MAS NMR) measurements confirmed the successful grafting of 2-pyridinecarboxaldehyde and 6-methylpyridine-2-carboxaldehyde to the chitosan backbone and indicated that 47(±2)% of the NH2 groups were grafted for both C1 and C2. The use of C1-Cu(OAc)2 as a catalyst in the nitroaldol reaction led to 96(±1)% conversion and 19(±4)% enantiomeric excess (ee), while the use of C2-Cu(OAc)2 as a catalyst also promoted the nitroaldol reaction, affording almost quantitatively the expected 2-nitro-1-phenylethanol (98(±1)%) with 14.5(±1.5)% ee.

First-Row Late Transition Metals for Catalytic Alkene Hydrofunctionalisation: Recent Advances in C-N, C-O and C-P Bond Formation.

This review provides an outline of the most noteworthy achievements in the area of C-N, C-O and C-P bond formation by hydroamination, hydroalkoxylation, hydrophosphination, hydrophosphonylation or hydrophosphinylation reaction on unactivated alkenes (including 1,2- and 1,3-dienes) promoted by first-row late transition metal catalytic systems based on manganese, iron, cobalt, nickel, copper and zinc. The relevant literature from 2009 until mid-2017 has been covered.

Selective synthesis of mono- and bis-butenolide α-aminomethyl adducts.

The selective installation of α-methylamine residues at the butenolide core is described using α-bromomethylene-γ-butenolide and primary as well as secondary amines in methanol at 0 °C. The preparation of mono- and bis-butenolide α-adducts is described. Bis-γ-butenolide adducts as well as mono α-aminomethyl-γ-butenolides can be selectively obtained depending on the nature of the reacting primary amine. In contrast, the use of secondary amines allows two different pathways leading either to the expected amino derivatives or to the formation of a C-O bond.

New biosourced chiral molecularly imprinted polymer: Synthesis, characterization, and evaluation of the recognition capacity of methyltestosterone.

New biosourced chiral cross-linkers were reported for the first time in the synthesis of methyltestosterone (MT) chiral molecularly imprinted polymers (cMIPs). Isosorbide and isomannide, known as 1,4:3,6-dianhydrohexitols, were selected as starting diols. The cMIPs were synthesized following a noncovalent approach via thermal radical polymerization and monitored by Raman spectroscopy. These cross-linkers were fully characterized by 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry. The cross-polarization magic angle spinning 13 C NMR, Fourier transform infrared spectroscopy, scanning electron microscopy, and specific surface areas following the Brunauer-Emmett-Teller (BET) method were used to characterize the cMIPs. The effect of stereochemistry of cross-linkers on the reactivity of polymerization, morphology, and adsorption-recognition properties of the MIP was evaluated. The results showed that the cMIP exhibited an obvious improvement in terms of rebinding capacity for MT as compared with the nonimprinted polymer (NIP). The highest binding capacity was observed for cMIP-Is (27.298 mg g-1 ) for high concentrations (500 mg L-1 ). However, the isomannide homologue cMIP-Im showed higher recovery-up to 65% and capacity for low concentrations (15 mg L-1 ). The experimental data were properly fitted by the Freundlich adsorption isothermal model.

From α-Bromomethylbutenolide to Fused Tri(Tetra) Cyclic Dihydrofurandiones through Barbier Reaction-Heck Arylation Sequence.

A Barbier reaction-Heck arylation sequence from α-bromomethylbutenolide to fused tri and tetracyclic lactones has been developed. The first step involving a Barbier reaction enabled installing ortho-bromoaromatics in α-ylidene γ-lactones. The latter substrates were subjected to intramolecular Heck reaction conditions which selectively afforded 6,5,5 or 6,6,5 fused ring systems depending on the nature of the base employed.

New biosourced AA and AB monomers from 1,4:3,6-dianhydrohexitols, Isosorbide, Isomannide, and Isoidide.

In the present work, we propose the synthesis of a new family of sugar derived 1,4:3,6-dianhydrohexitol based AA/AB-type monomers. Unprecedented diacids based on Isomannide and Isoidide were elaborated with high yields and showed interestingly high melting point ranges (240-375 °C). Optimization of reaction conditions (temperature, time of reaction, and reactant ratios) has been investigated to synthesize the key intermediate of a set of AB monomers with acid, ester, and acid chloride functionalities. Isosorbide based ether benzoic acid AB monomer was polymerized and characterized by NMR and DSC techniques. The results show a semicrystalline behavior of the obtained polymer thanks to the controlled stereoregular arrangement of the AB starting monomer.