Dynamic combinatorial chemistry as a tool for the design of functional materials and devices

This tutorial review presents emerging lines of investigations directed towards the development of dynamic combinatorial materials and devices. These can be defined as multi-component chemical systems which, thanks to the reversibility of their interconnections within networks of competing reactions, and thanks to their sensitivity to environmental parameters, aim at performing modular functional tasks by responding to external stimuli. The behaviour of such dynamic materials is by essence more complex than the one produced by their static or single-component counterparts and as such, they hold higher potentialities in terms of information processing and functionality tuning. Key examples are selected here to illustrate the variety of their chemical nature and physical properties which can be implemented for the fabrication of devices as diverse as sensors, ion channels, self-healable materials, mesophases for the controlled release of bioactive compounds, or dynamic functional nanostructures.     

Bis(oxalato)chromium(III) complexes: Versatile tectons in designing heterometallic coordination compounds

The mononuclear oxalato-containing chromium(III) complexes of general formula [Cr(AA)(C₂O₄)₂]^? (AA = α-diimine type ligand) are able to produce a large variety of heterometallic complexes by acting as ligands towards either fully solvated metal ions or preformed cationic complexes with available coordination sites. This review focuses on the structural diversity of the polynuclear complexes (oligonuclear and coordination polymers) which are generated by the bis(oxalato)chromate(III) species, with a special emphasis to their magnetic properties.     

Exploring the high-mass components of humic acid by laser desorption ionization mass spectrometry

Leonardite and Elliot soil humic acids have been analyzed by laser desorption ionization mass spectrometry (LDI MS) in the m/z 4000-200,000 range. Positive ion mass spectra for each humic acid obtained under optimum conditions showed a broad high-mass distribution between m/z 20,000 and 80,000. The dependence of the mass distribution on instrumental parameters and solution conditions was used to investigate the nature of the high-mass peaks from humic acid spectra. Our data suggests that macromolecular ions and humic acid aggregates have the same probability of occurrence while cluster ion formation has a low probability of occurrence.     

Electroweak precision data and right-handed gauge bosons

The implication of recent electroweak precision data for left-right symmetric models is examined. We establish a lower bound on the charged and neutral right-handed gauge bosons independent of the right-handed neutrino mass and of any restrictions or implied symmetries on the right KM matrix.     

Quadratic decomposition of orthogonal polynomials: a matrix approach

We consider a scalar orthogonal polynomial set associated with a regular functional. Its quadratic decomposition allows us to consider 2×2 matrix orthogonal polynomials whose coefficients are the components of the mentioned decomposition. The connection between the recurrence relations is given.Partially supported by an Acción Integrada Hispano-Portuguesa, no. 28 B/91.Realized in part during a stay in Paris, Lab. Analyse Numérique, Univ. Pierre et Marie Curie — CNRS, granted by MEC(Spain)/MRT(France) FR91.     

Initial-boundary value problem for the nonlinear string-beam system

This paper deals with a nonlinear string-beam system describing the torsional-vertical oscillations of a suspension bridge. We consider the initial-boundary value problem and study the existence and uniqueness question. We assume time independent right hand sides, but allow quite general nonlinear terms. Using the Faedo-Galerkin method we prove the existence of a unique solution on an arbitrary large time interval.     

Copper(II) complexes of 2-(pyridine-2-yl)imidazolidine-4-thione derivatives for asymmetric Henry reactions

The preparation of a new series of 2-(pyridine-2-yl)imidazolidine-4-thione derivatives is described. Their corresponding copper(II) complexes were found to be highly enantioselective catalysts for asymmetric Henry reactions (up to 98% ee). Immobilization of these complexes by anchoring onto Merrifield? resin with respect to their use as recyclable catalysts was subsequently performed. The heterogeneous catalysts prepared in this way were tested in the asymmetric Henry reactions and showed high catalytic activity; they can be easily recycled, although their enantioselectivities were only moderate (～50% ee).     

Monitoring of Portland cement chemical reaction and quantification of the hydrated products by XRD and TG in function of the stoppage hydration technique

Journal of Thermal Analysis and Calorimetry - Cement hydration occurs according to a sequence of reactions whose products have a direct influence on the working properties of concretes and mortars...     

Synthesis of Fucose-Containing Disaccharides by Glycosylhydrolases from Various Origins

Applied Biochemistry and Biotechnology - Glycosylhydrolases of various origins were used to produce fucose-containing disaccharides with prebiotic potential using different donor substrates and...