Nouvelles substances d'intercomparaison proposees pour l'etalonnage en temperature et en energie d'analyseurs thermiques (ou calorimetriques) differentiels

Several organic compounds as new reference materials for temperature and energy calibration of DTA and DSC appartuses were studied in the range of temperature 300–600 K.

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Zusammenfassung Im Temperaturbereich 300–600 K wurden einige organische Verbindungen als neue Referenzsubstanzen für die Temperatur- und Energieeichung bei DTA und DSC untersucht.

     

Localized Mixed‐Valence and Redox Activity within a Triazole‐Bridged Dinucleating Ligand upon Coordination to Palladium

The new dinucleating redox‐active ligand ( L^H4 ), bearing two redox‐active NNO‐binding pockets linked by a 1,2,3‐triazole unit, is synthetically readily accessible. Coordination to two equivalents of Pd^II resulted in the formation of paramagnetic (S= ) dinuclear Pd complexes with a κ²‐N,N′‐bridging triazole and a single bridging chlorido or azido ligand. A combined spectroscopic, spectroelectrochemical, and computational study confirmed Robin–Day Class II mixed‐valence within the redox‐active ligand, with little influence of the secondary bridging anionic ligand. Intervalence charge transfer was observed between the two ligand binding pockets. Selective one‐electron oxidation allowed for isolation of the corresponding cationic ligand‐based diradical species. SQUID (super‐conducting quantum interference device) measurements of these compounds revealed weak anti‐ferromagnetic spin coupling between the two ligand‐centered radicals and an overall singlet ground state in the solid state, which is supported by DFT calculations. The rigid and conjugated dinucleating redox‐active ligand framework thus allows for efficient electronic communication between the two binding pockets.     

Chemically Non‐Innocent Cyclic (Alkyl)(Amino)Carbenes: Ligand Rearrangement,C−H and C−F Bond Activation

A cyclic (alkyl)(amino)carbene (CAAC) was found to undergo unprecedented rearrangements and transformations of its core structure in the presence of Group 1 and 2 metals. Although the carbene was also found to be prone to intramolecular C?H activation, it was competent for intermolecular activation of a variety of sp‐, sp²‐, and sp³‐hybridized C?H bonds. Double C?F activation of hexafluorobenzene was also observed in this work. These processes all hold relevance to the role of these carbenes in catalysis, as well as to their use in the synthesis of new and unusual main group or transition metal complexes.     

Cost and sensitivity of restricted active‐space calculations of metal L‐edge X‐ray absorption spectra

The restricted active‐space (RAS) approach can accurately simulate metal L‐edge X‐ray absorption spectra of first‐row transition metal complexes without the use of any fitting parameters. These characteristics provide a unique capability to identify unknown chemical species and to analyze their electronic structure. To find the best balance between cost and accuracy, the sensitivity of the simulated spectra with respect to the method variables has been tested for two models, [FeCl₆]^3– and [Fe(CN)₆]^3–. For these systems, the reference calculations give deviations, when compared with experiment, of ≤1 eV in peak positions, ≤30% for the relative intensity of major peaks, and ≤50% for minor peaks. When compared with these deviations, the simulated spectra are sensitive to the number of final states, the inclusion of dynamical correlation, and the ionization potential electron affinity shift, in addition to the selection of the active space. The spectra are less sensitive to the quality of the basis set and even a double‐ζ basis gives reasonable results. The inclusion of dynamical correlation through second‐order perturbation theory can be done efficiently using the state‐specific formalism without correlating the core orbitals. Although these observations are not directly transferable to other systems, they can, together with a cost analysis, aid in the design of RAS models and help to extend the use of this powerful approach to a wider range of transition metal systems. © 2015 Wiley Periodicals, Inc.     

Organocatalytic synthesis of novel renewable non‐isocyanate polyhydroxyurethanes

Novel fully renewable AA‐BB type non‐isocyanate polyhydroxyurethanes were synthesized by the classical reaction between a diamine and a dicyclocarbonate. Sebacic acid was first reacted with an excess of glycerol carbonate, in presence of DCC and DMPA, leading to a renewable dicyclocarbonate monomer. Then, this monomer was reacted with several renewable diamines, in presence of 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD), as organocatalyst, to afford linear and branched polymers. The obtained materials exhibited T_g values varied from ?27 to ?8 °C, T_m values varying from 100 to 165 °C, and thermal stabilities above 200 °C. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 758–764     

Electron emission in ferroelectrics for different values of the coercive field

Results are presented of experimental studies of electron emission from single crystals of triglycine sulfate, nominally pure and doped with Cr³⁺. The relation between the parameters of the processes of switching and electron emission from ferroelectrics by a coercive field and the threshold field for the onset of emission is investigated. It is shown that the temperature and concentration dependences of the threshold field can be explained by the corresponding dependences of the coercive field. Fiz. Tverd. Tela (St. Petersburg) 41, 1675–1678 (September 1999)     

Bounded list injective homomorphism for comparative analysis of protein–protein interaction graphs

Comparing genomic properties of multiple species at varying evolutionary distances is a powerful approach for studying biological and evolutionary principles. In the context of comparative analysis of protein–protein interaction graphs, we use a graph-based formalism to detect the preservation of a given protein complex. We show that the problem is polynomial-time solvable provided that each protein has at most two orthologs in the other species, but is hard for three. Also, we suggest ways to cope with hardness by proposing three translations of the problem into well-known combinatorial optimization problems, thereby allowing the use of many recent results in fast exponential-time algorithms. Motivated by the need for more accurate models, we conclude by giving and discussing three natural extensions of the problem.     

New Components Including Cyclopeptides from Barks of Christiana africana DC. (Tiliaceae)

Phytochemical investigation of barks of Christiana africana led to the identification of cyclopeptide alkaloids, flavonoids, coumarinolignans, iridoids, sesquiterpenoids, and triterpenes. This plant was classified so far in the Tiliaceae family. This study was started while the genomic study of numerous specimens was described in order to establish new criteria for Malvales botanical classification. In the present work, twenty components were identified, belonging to the three major classes of secondary metabolites: alkaloids, phenols, and terpenes. In the first class, cyclopeptides are well‐known compounds in Rhamnaceae and Sterculiaceae. Their presence in Malvaceae (in APG2 sensus) suggests a possible chemical link between the ex‐Tiliaceae and the Malvaceae.     

Investigation on the reactivity of nucleophilic radiohalogens with arylboronic acids in water: access to an efficient single-step method for the radioiodination and astatination of antibodies

Easy access to radioiodinated and ²¹¹At-labelled bio(macro)molecules is essential to develop new strategies in nuclear imaging and targeted radionuclide therapy of cancers. Yet, the labelling of complex molecules with heavy radiohalogens is often poorly effective due to the multiple steps and intermediate purifications needed. Herein, we investigate the potential of arylboron chemistry as an alternative approach for the late stage labelling of antibodies. The reactivity of a model precursor, 4-chlorobenzeneboronic acid (1) with nucleophilic iodine-125 and astatine-211 was at first investigated in aqueous conditions. In the presence of a copper(ii) catalyst and 1,10-phenanthroline, quantitative radiochemical yields (RCYs) were achieved within 30 minutes at room temperature. The optimum conditions were then applied to a CD138 targeting monoclonal antibody (mAb) that has previously been validated for imaging and therapy in a preclinical model of multiple myeloma. RCYs remained high (>80% for ¹²⁵I-labelling and >95% for ²¹¹At-labelling), and the whole procedure led to increased specific activities within less time in comparison with previously reported methods. Biodistribution study in mice indicated that targeting properties of the radiolabelled mAb were well preserved, leading to a high tumour uptake in a CD138 expressing tumour model. The possibility of divergent synthesis from a common modified carrier protein demonstrated herein opens facilitated perspectives in radiotheranostic applications with the radioiodine/²¹¹At pairs. Overall, the possibility to develop radiolabelling kits offered by this procedure should facilitate its translation to clinical applications.

The high reactivity of astatine and iodine in water with arylboronic acids provides access to an efficient single-step antibody radiolabelling.     

First Representatives of Adamantyl-containing Amidrazones

Russian Journal of General Chemistry -