Thiol-yne photoclick polymerization as a method for preparing imidazolium-containing ionene networks

Herein, the thiol-yne photoclick reaction was utilized as a method for synthesizing imidazolium-containing ionene networks whereby a bisalkynyl-functionalized imidazolium [NTf₂] ionic liquid was polymerized with the tetrafunctional thiol PTMP (pentaerythritol tetrakis(3-mercaptopropionate)). The thiol:yne functional group ratio was varied in order to examine the breadth of thermal, mechanical, and conductive properties available from the resulting networks. The stoichiometric 1:1 thiol:yne network exhibited very high thiol and alkyne conversions by FT-IR spectroscopy and a gel fraction greater than 95%. The highest T_g value (3.5°C) and stress at break (1.13 MPa) were also observed for this network. As either thiol or alkyne functional group concentration was increased, the networks were noticeably lower in T_g and stress at break with a modest increase in % elongation. Ionic conductivities were found to be on the order of 10⁻⁹ to 10⁻⁷ S/cm at 30°C. Normalization of the ionic conductivity curves did not lead to a complete collapse meaning that the observed differences in conductivity are not solely dependent upon T_g. When compared to analogous imidazolium-containing, thiol-ene ionene networks, the thiol-yne networks were found to be slightly more mechanically robust, but approximately one order of magnitude lower in terms of ionic conductivity.     

Recent applications of thiol-ene coupling as a click process for glycoconjugation

There has been over the past decades a resurgence of the free-radical thiol-ene coupling (TEC) as a method for assembling crosslinked networks and polymer functionalization. On the other hand the use of TEC in carbohydrate chemistry, a field of special importance due to the key role of carbohydrates in living organisms, is represented only by a handful of papers. Nevertheless it appears that TEC possesses many if not all the attributes of a click process proceeding with the assistance of the greenest catalyst such as visible light. This tutorial review focuses on the application of TEC on different topics, all related to glycochemistry, including: (a) carbohydrate modification, (b) oligosaccharide and glycosyl amino acid synthesis, (c) assembly of glycoclusters on rigid molecular platforms (calixarene, cyclodextrin, silsesquioxane, dendrimer), (d) peptide and protein glycosylation. Also the very recent development in peptide glycosylation by the closely related thiol-yne chemistry is described.     

Luminophoric organic molecules for anticounterfeit printing ink applications: an up-to-date review

Counterfeiting of currency, valuable documents, and branded products remains an extremely challenging concern for governments, companies, and consumers worldwide, which poses grave monetary, safety, and health consequences. In recent years, organic luminescent materials are being widely used in various fields, especially in advanced optical displays and solid-state lighting as they exhibit exceptional optical properties and chemical stability. These features facilitated the use of organic luminophores as highly promising materials in anticounterfeiting applications too. This review introduces the concerns due to counterfeiting, introduces various techniques to combat the growing threat, and further acknowledges the different types of luminophores currently used in antiforging applications. The article mainly highlights the recent developments in organic solvent-based and eco-friendly water-based formulations for anticounterfeiting purposes that contain organic molecules with various unique features as fluorescent pigments. Furthermore, the limitations of the currently used organic materials and future prospects for fabricating smart luminogens to tackle the counterfeiting problems are also discussed. This review would benefit researchers who are currently working and those who have just entered this fascinating and evolving, but highly demanding, area of security printing.     

Conjugated macrocycles: concepts and applications

One of the most important objectives in materials, chemical, and physical sciences is the creation of large conjugated macrocycles with well-defined shapes, since such molecules are not only theoretically and experimentally interesting but also have potential applications in nanotechnology. Fully unsaturated macrocycles are regarded as models for infinitely conjugated π systems with inner cavities, and exhibit unusual optical and magnetic behavior. Macrocycles have interior and exterior sites, and site-specific substitution at both or either site can afford attractive structures, such as 1D, 2D, and 3D supramolecular nanostructures. These nanostructures could be controlled through the use of π-extended large macrocycles by a bottom-up strategy. Numerous shape-persistent π-conjugated macrocycles have been synthesized, but only a few are on the nanoscale. This Review focuses on nanosized π-conjugated macrocycles (>1 nm diameter) and giant macrocycles (>2 nm diameter), and summarizes their syntheses and properties.     

Polymer therapeutics: concepts and applications

Polymer therapeutics encompass polymer-protein conjugates, drug-polymer conjugates, and supramolecular drug-delivery systems. Numerous polymer-protein conjugates with improved stability and pharmacokinetic properties have been developed, for example, by anchoring enzymes or biologically relevant proteins to polyethylene glycol components (PEGylation). Several polymer-protein conjugates have received market approval, for example the PEGylated form of adenosine deaminase. Coupling low-molecular-weight anticancer drugs to high-molecular-weight polymers through a cleavable linker is an effective method for improving the therapeutic index of clinically established agents, and the first candidates have been evaluated in clinical trials, including, N-(2-hydroxypropyl)methacrylamide conjugates of doxorubicin, camptothecin, paclitaxel, and platinum(II) complexes. Another class of polymer therapeutics are drug-delivery systems based on well-defined multivalent and dendritic polymers. These include polyanionic polymers for the inhibition of virus attachment, polycationic complexes with DNA or RNA (polyplexes), and dendritic core-shell architectures for the encapsulation of drugs. In this Review an overview of polymer therapeutics is presented with a focus on concepts and examples that characterize the salient features of the drug-delivery systems.     

A truce on the Smiles rearrangement: revisiting an old reaction--the Truce-Smiles rearrangement

The Smiles rearrangement is the intramolecular nucleophilic aromatic substitution reaction incorporating a heteroatom as the nucleophilic component and an activated electrophilic arene. One particular variation--the Truce-Smiles rearrangement--utilises a carbon-based nucleophile and an electrophilic arene which does not require additional activation. Such a variation generates a new carbon-carbon bond and the synthetic utility of this relatively under-utilised rearrangement is discussed in this tutorial review.     

Organometallic catalysis: From concepts to selected applications

This article is devoted to the use of some concepts of organometallic chemistry for their application in homogeneous catalysis developed in our laboratory in Lille and presented in the Gecom-Concoord meeting in Albé. The first examples will deal with the use of bifunctional ligands, where it will be shown that designing an aminophosphine ligand allows one to improve the rate of linear dimerization of dienic substrates by two orders of magnitude, as compared with the same reaction conducted in protic media. Another application will concern the use of the hemilability character of a suitable methoxy substituted, sterically hindered alcoxy ligand, responsible for the original metathesis reaction of terminal acetylenes. The second part will be devoted to the use of transmetalation reactions, at first in polymerization reactions, where the concept of Coordinative Catalyzed Chain Growth Transfer will be established using Lanthanide complexes and magnesium dialkyls, applied to olefins, conjugated dienes, styrene and isoprene/styrene statistical copolymerization. The last topic will develop carbonylation reactions using boronic acids and enones or alkynes, in which the key step is a transmetalation/carbonylation sequence, opening the way to new catalytic carbonylation processes.     

Review: Lanthanide coordination chemistry: from old concepts to coordination polymers

Because of their remarkable and unmatched optical and magnetic properties, the lanthanides are under the limelight when it comes to high technology. These elements are used in strategic applications such as optical glasses and lasers, telecommunications, lighting and displays, magnetic materials, hard-disk drives, security inks and counterfeiting tags, catalysis, biosciences, and medicine, to name but a few. Long considered as minor actors in transition metal chemistry, they have now gained respect from coordination chemists who insert them into sophisticated functional and polyfunctional molecules and materials. This mini review focuses on trivalent lanthanide ions and first summarizes their basic properties. Then some classical aspects of their coordination chemistry are discussed, followed by macrocyclic chemistry, supramolecular chemistry, and self-assembly processes. The last part of this contribution deals with coordination polymers and hybrid materials including potential applications.     

Synthesis and applications of polyvinylpyridine-grafted silica containing palladium nanoparticles as a new heterogeneous catalyst for heck and suzuki coupling reactions

A new catalytic system based on palladium nanoparticles supported on poly(4-vinylpyridine) (P4VPy)-grafted silica is introduced. Aminopropylsilica was reacted with acryloyl chloride to form acrylamidopropylsilica. Onto this functionalized silica, 4-vinylpyridine monomer was polymerized by free radical polymerization. The P4VPy-grafted silica was characterized by FT-IR spectroscopy and the amount of (P4VPy) grafted was determind by thermogravimetric analysis (TGA). The complexation of (P4VPy)-grafted silica with Pd(Cl)₂ was carried out to obtain the heterogeneous catalytic system. Transmission electron microscopy images (TEM) showed that palladium dispersed through polymer surface in nanoparticle size. This catalytic system exhibited excellent activity in cross-coupling reactions of aryl iodides, bromides and also chlorides, with olefinic compounds in Heck-Mizoraki, and with benzylbronic acid in Suzuki-Miyaura reactions. The use of aryl chlorides in cross-coupling reactions is usually hardly successful, but excellent results were gained in the presence of terta-n-butylammonium bromide (TBAB) as an additive. The turnover number (TON) of this catalyst reaches up to 9 × 10⁴ in these C-C bond forming reactions. High efficiency of the catalyst along with short reaction time, high yields, easy purification, recyclability, large scale synthesis and simple procedure are among the advantages of this catalytic system     

Structure and reactivity of radical ions: new twists on old concepts

Electron transfer is the simplest reaction possible, yet it has a profound impact on the structure and reactivity of organic compounds. These changes allow a new look at some of the fundamental concepts that are used to explain organic chemistry, such as symmetry, aromaticity, and bonding. The results from high-level electronic structure calculations are used to analyze the mechanistic differences in the pericyclic reactions of simple hydrocarbons and their radical cation counterparts. The importance of state symmetry correlation, Jahn-Teller distortions, delocalization, and fractional bonding for the reaction pathways of hydrocarbon radical cations is discussed.     

The electron–nucleus coupling: A breakthrough in the investigation of paramagnetic metalloproteins

Water proton relaxation measurements as a function of magnetic field on solutions containing paramagnetic metalloproteins contain information on (i) number and distance of metal-coordinated water molecules, (ii) dynamics of water exchange, (iii) electron relaxation rates, and (iv) dynamics of the metal coordination sphere influencing electron relaxation. The use of appropriate theoretical tools permits us in many cases to learn about some or all of the above properties.     

Vinyldisiloxanes: their synthesis, cross coupling and applications

During the studies towards the development of pentafluorophenyldimethylsilanes as a novel organosilicon cross coupling reagent it was revealed that the active silanolate and the corresponding disiloxane formed rapidly under basic conditions. The discovery that disiloxanes are in equilibrium with the silanolate led to the use of disiloxanes as cross coupling partners under fluoride free conditions. Our previous report focused on the synthesis and base induced cross coupling of aryl substituted vinyldisiloxanes with aryl halides; good yields and selectivities were achieved. As a continuation of our research, studies into the factors which influence the successful outcome of the cross coupling reaction with both alkyl and aryl substituted vinyldisiloxanes were examined and a proposed mechanism discussed. Further investigation into expanding the breadth and diversity of substituted vinyldisiloxanes in cross coupling was explored and applied to the synthesis of unsymmetrical trans-stilbenes and cyclic structures containing the trans-alkene architecture.     

Vibronic coupling in quantum wires: applications to polydiacetylene

A theory describing vibronic coupling in direct band gap, one-dimensional semiconductors is developed to account for the photophysical properties of isolated, defect-free conjugated polymers. A Holstein-like Hamiltonian represented in a multi-particle basis set is used to evaluate absorption and emission due to Wannier-Mott excitons. The photophysical properties of such quantum wires are shown to strongly resemble those of Frenkel exciton J-aggregates. The 1(1)B(u) exciton coherence length and effective mass are readily determined from the ratio of the 0-0 and 0-1 line strengths, I(0 - 0)/I(0 - 1), in the photoluminescence spectrum. I(0 - 0)/I(0 - 1) is shown to follow a T(-1/2) dependence, in an excellent agreement with experiments on the red-phase of polydiacteylene.     

Dialdehyde cellulose as a niche material for versatile applications: an overview

Cellulose - Dialdehyde cellulose (DAC) has garnered substantial scientific interest, thanks to broad spectrum of possible chemical reactions offered by the aldehyde moieties in its backbone. In the...     

The pseudouridine synthases: revisiting a mechanism that seemed settled

RNA containing 5-fluorouridine, [f 5U]RNA, has been used as a mechanistic probe for the pseudouridine synthases, which convert uridine in RNA to its C-glycoside isomer, pseudouridine. Hydrated products of f 5U were attributed to ester hydrolysis of a covalent complex between an essential aspartic acid residue and f 5U, and the results were construed as strong support for a mechanism involving Michael addition by the aspartic acid residue. Labeling studies with [18O]water are now reported that rule out such ester hydrolysis in one pseudouridine synthase, TruB. The aspartic acid residue does not become labeled, and the hydroxyl group in the hydrated product of f 5U derives directly from solvent. The hydrated product, therefore, cannot be construed to support Michael addition during the conversion of uridine to pseudouridine, but the results do not rule out such a mechanism. A hypothesis is offered for the seemingly disparate behavior of different pseudouridine synthases toward [f 5U]RNA.     

Capillary electrophoresis in clinical and forensic analysis: recent advances and breakthrough to routine applications

This paper is a comprehensive review article on capillary electrophoresis (CE) in clinical and forensic analysis. It is based upon the literature of 1997 and 1998, presents CE examples in major fields of application, and provides an overview of the key achievements encountered, including those associated with the analysis of drugs, serum proteins, hemoglobin variants, and nucleic acids. For CE in clinical and forensic analysis, the past two years witnessed a breakthrough to routine applications. As most coauthors of this review are associated with diagnostic or forensic laboratories now using CE on a routine basis, this review also contains data from routine applications in drug, protein, and DNA analysis. With the first-hand experience of providing analytical service under stringent quality control conditions, aspects of quality assurance, assay specifications for clinical and forensic CE and the pros and cons of this maturing, cost-and pollution-controlled age technology are also discussed.     

Fibre optic coupler as a detector for microfluidic applications

A new construction of a fibre optic coupler is presented in the paper. Two polymer optical fibres were used to build a coupler in which coupling efficiency of optical power depends on the refractive index of liquid delivered to a microchannel formed by the fibres. The coupler was tested as a detector in saccharose concentration measurements, and was used in absorbance measurements. A red light emitting diode and a spectrometer were used as a light source and a photodetector, respectively. Experiments confirmed that the coupler can be used for the real time monitoring of the changes in the refractive index of a saccharose solution exhibiting repeatable changes in the signal, with no hysteresis. Absorbance tests were performed with a solution of bromothymol blue at different pH.     

Structural bioinformatics: methods,concepts and applications to blood coagulation proteins

Structural and theoretical analyses of proteins are central to the understanding of complex molecular mechanisms and are fundamental to the drug discovery process. Computational techniques yield useful insights into an ever-wider range of biomolecular systems. Protein three-dimensional structures and molecular functions can be predicted in some circumstances, while experimental structures can be analyzed in depth via such computational approaches. Non-covalent binding of biomolecules can be understood by considering structural, thermodynamic and kinetic issues, and theoretical simulations of such events can be attempted. The central role of electrostatic interactions with regard to protein function, structure and stability has been investigated and some electrostatic properties can be modeled theoretically. Computer methods thus help to prioritize, design, analyze and rationalize biochemical experiments. Cardiovascular diseases and associated blood coagulation disorders are leading causes of death worldwide. Blood coagulation involves more than 30 proteins that interact specifically with various degrees of affinity. Many of these molecules can also bind transiently to phospholipid surfaces. Numerous point mutations in the genes of coagulation proteins and regulators have been identified. Understanding the coagulation cascade, its regulation and the impact of mutations is required for the development of new therapies and diagnostic tools. In this review, we describe concepts and methods pertaining to the field of structural bioinformatics. We provide examples of applications of these approaches to blood coagulation proteins and show that such studies can give insights about molecular mechanisms contributing to cardiovascular disease susceptibility.