Diaqua(oxydiacetato‐κ3O,O′,O′′)(pyridine‐3‐carboxamide‐κN1)copper(II)

In the mononuclear title compound, [Cu(C₄H₄O₅)(C₆H₆N₂O)(H₂O)₂], the Cu^II centre is bound to a chelating oxydiacetate ligand, a monodentate pyridine‐3‐carboxamide unit and two water molecules, defining an octahedral coordination where the first two ligands form the equatorial plane and the last two occupy the apical sites. The planar oxydiacetate ligand is slightly disordered at its central ether O atom. The availability of efficient donors and acceptors for hydrogen bonding results in a complex interaction scheme where each monomer links to six similar units to define a well connected three‐dimensional structure. A comparison is made with related structures in the literature, and the reasons for their differences are discussed.     

Constitutive equations for an electroactive polymer

Ionic electroactive polymers can be used as sensors or actuators. For this purpose, a thin film of polyelectrolyte is saturated with a solvent and sandwiched between two platinum electrodes. The solvent causes a complete dissociation of the polymer and the release of small cations. The application of an electric field across the thickness results in the bending of the strip and vice versa. The material is modeled by a two-phase continuous medium. The solid phase, constituted by the polymer backbone inlaid with anions, is depicted as a deformable porous media. The liquid phase is composed of the free cations and the solvent (usually water). We used a coarse grain model. The conservation laws of this system have been established in a previous work. The entropy balance law and the thermodynamic relations are first written for each phase and then for the complete material using a statistical average technique and the material derivative concept. One deduces the entropy production. Identifying generalized forces and fluxes provides the constitutive equations of the whole system: the stress–strain relations which satisfy a Kelvin–Voigt model, generalized Fourier’s and Darcy’s laws and the Nernst–Planck equation.     

The Critical Fugacity for Surface Adsorption of Self-Avoiding Walks on the Honeycomb Lattice is {1+\sqrt{2}}

In 2010, Duminil-Copin and Smirnov proved a long-standing conjecture of Nienhuis, made in 1982, that the growth constant of self-avoiding walks on the hexagonal (a.k.a. honeycomb) lattice is ${\mu=\sqrt{2+\sqrt{2}}}$ . A key identity used in that proof was later generalised by Smirnov so as to apply to a general O(n) loop model with ${n\in [-2,2]}$ (the case n = 0 corresponding to self-avoiding walks). We modify this model by restricting to a half-plane and introducing a surface fugacity y associated with boundary sites (also called surface sites), and obtain a generalisation of Smirnov’s identity. The critical value of the surface fugacity was conjectured by Batchelor and Yung in 1995 to be ${y_{\rm c}=1+2/\sqrt{2-n}}$ . This value plays a crucial role in our generalized identity, just as the value of the growth constant did in Smirnov’s identity. For the case n = 0, corresponding to self-avoiding walks interacting with a surface, we prove the conjectured value of the critical surface fugacity. A crucial part of the proof involves demonstrating that the generating function of self-avoiding bridges of height T, taken at its critical point 1/μ, tends to 0 as T increases, as predicted from SLE theory.     

Benzo[1,2‐d:4,5‐d′]bisimidazoles as a Convenient Platform Towards Dyes that are Capable of Excited‐State Intramolecular Proton Transfer and of Two‐Photon Absorption

New, strongly fluorescent benzo[1,2‐d:4,5‐d′]bisimidazoles have been prepared by the reaction of Bandrowski′s base with various aldehydes. Their structures were carefully designed to achieve efficient excited‐state intramolecular proton transfer and good two‐photon‐absorption (2PA) cross‐sections. Functional dyes that possessed both high fluorescence quantum yields and large Stokes shifts were prepared. A π‐expanded D‐A‐D derivative that possessed Φ_fl=50 % and σ₂=230 GM in the spectroscopic area of interest for biological imaging is an excellent candidate as a fluorescent probe. Thanks to the presence of two reactive amino groups, such compounds can be easily transformed into probes for bioconjugation. All of these benzo[1,2‐d:4,5‐d′]bisimidazoles were also strongly fluorescent in the solid state.     

Octupolar Derivatives Functionalized with Superacceptor Peripheral Groups: Synthesis and Evaluation of the Electron‐Withdrawing Ability of Potent Unusual Groups

Novel tripodal derivatives with a triphenylamine core and that bear “superacidifiers” (i.e., fluorinated sulfoximinyl blocks) or novel sulfiliminyl moieties as peripheral groups were synthesized. These new chromophores show strong absorption in the near‐UV region and emission in the visible region. The fluorinated sulfoximinyl moieties were found to behave as potent auxochromic and electron‐withdrawing (EW) groups, thus leading to redshifted absorption and emission. These moieties promote a core‐to‐periphery intramolecular charge transfer (ctp‐ICT) transition, the energy of which was found to be correlated to their EW strength. In this study, we provide evidence of a linear correlation between the Hammett constant (σ_p) values and the electronic gap between the ground and first excited state of the three‐branched derivatives. This in turn was used to derive σ_p values of fluorinated sulfoximinyl moieties. These EWGs show unprecedentedly high σ_p values, up to 1.45 relative to 0.8 for NO₂. Also, by using this method, the sulfiliminyl moiety was shown to exhibit similar EW strength as NO₂, while promoting improved transparency and solubility. Finally, the superior EW strength of the fluorinated sulfoximine peripheral moieties was shown to induce significant enhancement of the two‐photon absorption responses in the red near‐IR region of the three‐branched derivatives relative to similar octupoles that bear more usual strong EW groups. These characteristics (improved nonlinear responses or transparency) open new routes for the design of nonlinear optical (NLO) chromophores for optical limiting or electro‐optical modulation. Such building blocks could also be of interest for optoelectronic applications, including the development of solar cells.     

Triaquatris(μ‐oxydiacetato)dipraseodymium(III) pentahydrate and hexaaquatris(μ‐oxydiacetato)dineodymium(III) oxydiacetic acid solvate dihydrate

Two new complexes of the Ln₂(oda)₃·nH₂O (oda =–O₂CCH₂OCH₂CO₂–) series are reported, i.e. {[Pr₂(C₄H₄O₅)₃(H₂O)₃]·5H₂O}_n and {[Nd₂(C₄H₄O₅)₃(H₂O)₆]·C₄H₆O₅·‐2H₂O}_n. The former is isostructural with the reported La analogue, while the latter is a new structural variety within the series. Each compound exhibits two independent nine‐coordinated Ln centres showing a variety of coordination geometries.     

Stealth Luminescent Organic Nanoparticles Made from Quadrupolar Dyes for Two-Photon Bioimaging: Effect of End-Groups and Core

Molecular-based Fluorescent Organic Nanoparticles (FONs) are versatile light-emitting nano-tools whose properties can be rationally addressed by bottom-up molecular engineering. A challenging property to gain control over is the interaction of the FONs’ surface with biological systems. Indeed, most types of nanoparticles tend to interact with biological membranes. To address this limitation, we recently reported on two-photon (2P) absorbing, red to near infrared (NIR) emitting quadrupolar extended dyes built from a benzothiadiazole core and diphenylamino endgroups that yield spontaneously stealth FONs. In this paper, we expand our understanding of the structure-property relationship between the dye structure and the FONs 2P absorption response, fluorescence and stealthiness by characterizing a dye-related series of FONs. We observe that increasing the strength of the donor end-groups or of the core acceptor in the quadrupolar (D-π-A-π-D) dye structure allows for the tuning of optical properties, notably red-shifting both the emission (from red to NIR) and 2P absorption spectra while inducing a decrease in their fluorescence quantum yield. Thanks to their strong 1P and 2P absorption, all FONs whose median size varies between 11 and 28 nm exhibit giant 1P (10⁶ M⁻¹.cm⁻¹) and 2P (10⁴ GM) brightness values. Interestingly, all FONs were found to be non-toxic, exhibit stealth behaviour, and show vanishing non-specific interactions with cell membranes. We postulate that the strong hydrophobic character and the rigidity of the FONs building blocks are crucial to controlling the stealth nano-bio interface.     

Morse theory for some lower-C 2 functions in finite dimension

Using inf-regularization methods, we prove that Morse inequalities hold for some lower-C ² functions. For this purpose, we first recall some properties of the class of lower-C ² functions and of their Moreau-Yosida approximations. Then, we establish, under some qualification conditions on the critical points, that it is possible to define a Morse index for a lower-C ² functionf. This index is preserved by the Moreau-Yosida approximation process. We prove in particular that the Moreau-Yosida approximations are twice continuolusly differentiable around such a critical point which is shown to be a strict local minimum of the restriction off and of its approximations to some affine space. In a last step, Morse inequalities are written for Moreau-Yosida approximations and with the aid of deformation retractions we prove that these inequalities also hold for some lower-C ² functions.     

The role of bismuth as promoter in Pd–Bi catalysts for the selective oxidation of glucose to gluconate

Bismuth is a well-established promoter of noble metal-based catalysts for the selective liquid phase oxidation of alcohols, aldehydes and carbohydrates with molecular oxygen. Experiments were carried out to improve the understanding of the promoting role of bismuth in bimetallic Pd–Bi catalysts used for the selective oxidation of glucose to gluconate. In relationship with the fact that these catalysts undergo substantial bismuth leaching under the reaction conditions, particular attention was paid to the possible role played by the soluble fraction of bismuth in the oxidative process. Carbon-supported Pd–Bi/C catalysts characterized by various Bi–Pd compositions (0.33≤Bi/Pd≤3.0,10 wt.%Pd+Bi) were prepared from acetate-type precursors, tested under various experimental conditions and analyzed by X-ray diffractometry and X-ray photoelectron spectroscopy (XPS). Whatever the initial catalyst composition, the surface intensity ratio measured by XPS in used catalysts lies in the range 0.4–0.6, suggesting that the dynamic state of the catalyst involves the association of one Bi and two to three Pd atoms. The leaching process and the promoting effect itself are discussed in line with the formation of Bi–glucose and Bi–gluconate complexes present in solution but also as adsorbed species at the catalyst surface. The performances of a monometallic Pd/C catalyst are significantly improved in the presence of adequate amounts of soluble Bi. The involvement of the soluble fraction of bismuth in the overall mechanistic scheme of glucose oxidative dehydrogenation is suggested. The detrimental effect of large amounts of soluble bismuth is attributed to a too extensive adsorption of Bi–glucose complexes on the surface Pd atoms.     

Étude physico-chimique des substances thermomètres

Résumé Les auteurs ont donné un résumé de leurs recherches sur la pyrolyse de 32 substances qui changent de couleur entre 35 et 450° C et qui peuvent s'utiliser comme indicateurs de température. Les courbes de thermolyse ne sont pas reproduites à cause de leur simplicité. Les causes des changements de couleur sont variables. Dans quelques cas, il s'agit d'un changement d'état allotropique (dérivés du mercure) et l'on observe une réversibilité parfaite. Dans d'autres cas, sous l'action d'une reprise d'humidité, on revient à la teinte initiale. Enfin, comme la température de destruction dépend beaucoup du mode de préparation, de la vitesse de chauffe, de l'atmosphère environnante, certaines températures de virage ne doivent pas être considérées comme absolues. C'est pourquoi certaines de nos valeurs s'écartent de celles des auteurs précédents.

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Summary The writers have given a résumé of their investigations of the pyrolysis of 32 substances which change color between 35 and 450° C and which can be employed as temperature indicators. The thermolysis curves are not reproduced because of their simplicity. There are various reasons for these changes in color. In some instances a change in allotropic state is involved (mercury derivatives) and a perfect reversibility is observed. In other cases, the initial color is restored because of the recovery of moisture. Finally, since the temperature of destruction depends greatly on the method of preparation, the rate of heating and the surrounding atmosphere, certain color change temperatures should not be regarded as absolute. This explains the divergence of our values from those of previous workers.

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Zusammenfassung Über die Untersuchungen der Pyrolyse von 32 Substanzen, die zwischen 35 und 450° C ihre Farbe ändern und daher als Wärmeindikatoren dienen können, wird zusammenfassend berichtet. Die Thermolysekurven sind ihrer Einfachheit wegen nicht wiedergegeben. Die Ursachen der Farbänderung sind unterschiedlich. Mitunter handelt es sich um Polymorphien (Quecksilberverbindungen), die vollständig reversibel sind. In anderen Fällen führt die Wiederaufnahme von Wasser auch zur ursprünglichen Farbe. Da die Zersetzungstemperatur weitgehend von der Art der Darstellung des Präparates, der Geschwindigkeit des Erhitzens, der umgebenden Atmosphäre abhängt, sind manche Umwandlungspunkte nicht als Absolutwerte anzusehen. Aus diesem Grund ergaben sich auch Abweichungen gegenüber Angaben anderer Autoren.

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En l'honneur du ProfesseurFrite Feigl, pour son 70^e anniversaire.