On the Synthesis,Characterization and Reactivity of N‐Heteroaryl–Boryl Radicals,a New Radical Class Based on Five‐Membered Ring Ligands

The synthesis and physical characterization of a new class of N‐heterocycle–boryl radicals is presented, based on five membered ring ligands with a N(sp²) complexation site. These pyrazole–boranes and pyrazaboles exhibit a low bond dissociation energy (BDE; B?H) and accordingly excellent hydrogen transfer properties. Most importantly, a high modulation of the BDE(B?H) by the fine tuning of the N‐heterocyclic ligand was obtained in this series and could be correlated with the spin density on the boron atom of the corresponding radical. The reactivity of the latter for small molecule chemistry has been studied through the determination of several reaction rate constants corresponding to addition to alkenes and alkynes, addition to O₂, oxidation by iodonium salts and halogen abstraction from alkyl halides. Two selected applications of N‐heterocycle–boryl radicals are also proposed herein, for radical polymerization and for radical dehalogenation reactions.     

Click approaches in sol–gel chemistry

The combination of the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction with sol–gel processing enables the versatile preparation of sol–gel materials under different shapes with targeted functionalities through a diversity-oriented approach. In this account, the development of the CuAAC reaction under anhydrous conditions for the synthesis of sol–gel precursors and for the assembling of magnetic nanoparticles on self-assembled monolayers is related, as well as the use of the classical CuAAC methodologies for the functionalization of mesoporous silica nanoparticles and microdots arrays. Coupling CuAAC and Sol–Gel will result in simplified preparations of multifunctional materials with controlled morphologies.     

Characterization of Collagen/Lipid Nanoparticle–Curcumin Cryostructurates for Wound Healing Applications

Curcumin‐loaded collagen cryostructurates have been devised for wound healing applications. Curcumin displays strong antioxidant, antiseptic, and anti‐inflammatory properties, while collagen is acknowledged for promoting cell adhesion, migration and differentiation. However, when curcumin is loaded directly into collagen hydrogels, it forms large molecular aggregates and clogs the matrix pores. A double‐encapsulation strategy is therefore developed by loading curcumin into lipid nanoparticles (LNP), and embedding these particles inside collagen scaffolds. The resulting collagen/LNP cryostructurates have an optimal fibrous structure with ≈100 µm average pore size for sustaining cell migration. Results show that collagen is structurally unaltered and that nanoparticles are homogeneously distributed amidst collagen fibers. Hydrogels soaked in saline buffer release about 20 to 30% of their nanoparticles content within 24 h, while achieved 100% release after 25 days. When exposed to NIH 3T3 fibroblasts, these hydrogels provide a satisfactory scaffold for cell interaction as early as 4 h after seeding, with no cytotoxic counter effect. These positive features make the collagen/lipid cryostructurates a promising material for further use in wound healing.     

An Efficient RuII–RhIII–RuII Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution

The development of multicomponent molecular systems for the photocatalytic reduction of water to hydrogen has experienced considerable growth since the end of the 1970s. Recently, with the aim of improving the efficiency of the catalysis, single‐component photocatalysts have been developed in which the photosensitizer is chemically coupled to the hydrogen‐evolving catalyst in the same molecule through a bridging ligand. Until now, none of these photocatalysts has operated efficiently in pure aqueous solution: a highly desirable medium for energy‐conversion applications. Herein, we introduce a new ruthenium–rhodium polypyridyl complex as the first efficient homogeneous photocatalyst for H₂ production in water with turnover numbers of several hundred. This study also demonstrates unambiguously that the catalytic performance of such systems linked through a nonconjugated bridge is significantly improved as compared to that of a mixture of the separate components.     

Descent algorithm for nonsmooth stochastic multiobjective optimization

An algorithm for solving nearly-separable quadratic optimization problems (QPs) is presented. The approach is based on applying a semismooth Newton method to solve the implicit complementarity problem arising as the first-order stationarity conditions of such a QP. An important feature of the approach is that, as in dual decomposition methods, separability of the dual function of the QP can be exploited in the search direction computation. Global convergence of the method is promoted by enforcing decrease in component(s) of a Fischer–Burmeister formulation of the complementarity conditions, either via a merit function or through a filter mechanism. The results of numerical experiments when solving convex and nonconvex instances are provided to illustrate the efficacy of the method.     

Dispersive estimates and the 2D cubic NLS equation

We prove that the initial value problem for the 2D cubic semi-linear Schrödinger equation is well-posed in the Besov space B _0, ^∞2 (?²). For this, we rely on some new dispersive inequalities derived from bilinear restriction theorems.     

Trivalent Cation Substitution Effect into Layered Double Hydroxides Co2Fey Al1−y(OH)6Cl·nH2O: Study of the Local Order: Ionic Conductivity and Magnetic Properties

A series of layered double hydroxide materials of composition Co₂Fe_yAl_1−y(OH)₆Cl·nH₂O (0≤y≤1) was prepared via chimie douce. The crystalline parameter related to the cation to cation distance obeys the expected variation, showing that the substitution is effective over the entire range. Local order around Co and Fe cations is studied by X-ray absorption spectroscopy. Moduli of the Fourier transform at the Fe K-edge are superimposable, in agreement with an ordered model, although present in small domains since no superlattice is depicted. The ionic resistivity of the samples is highly dependent on the water molecule content. The conductivity is found to be thermally assisted, and the variation of the slope in the Arrhenius diagram is explained by a Vogel-Tamman-Fulcher-type behavior. Magnetic susceptibility measurements support the proposed cation composition and indicate the onset of local magnetic order at low temperature (below 10 K). The inter-sheet distance influences the magnetic response at low temperature, showing the presence of weak interactions between lamellae.