Showing papers in "Pure and Applied Chemistry in 2015"

Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report)

Abstract: Gas adsorption is an important tool for the characterisation of porous solids and fine powders. Major advances in recent years have made it necessary to update the 1985 IUPAC manual on Reporting Physisorption Data for Gas/Solid Systems. The aims of the present document are to clarify and standardise the presentation, nomenclature and methodology associated with the application of physisorption for surface area assessment and pore size analysis and to draw attention to remaining problems in the interpretation of physisorption data.

Standard electrode potentials involving radicals in aqueous solution: Inorganic radicals

Abstract: Recommendations are made for standard potentials involving select inorganic radicals in aqueous solution at 25 °C. These recommendations are based on a critical and thorough literature review and also by performing derivations from various literature reports. The recommended data are summarized in tables of standard potentials, Gibbs energies of formation, radical pKa’s, and hemicolligation equilibrium constants. In all cases, current best estimates of the uncertainties are provided. An extensive set of Data Sheets is appended that provide original literature references, summarize the experimental results, and describe the decisions and procedures leading to each of the recommendations

Boron clusters in medicinal chemistry: perspectives and problems

Abstract: Abstract Boron clusters have been employed successfully as constituents in bioactive substances. In this review, the perspectives of boron clusters for drug design and problems to be solved for a broader application are discussed, and a list of actions is given for overcoming the problems.

Mechanisms of removal of heavy metals and arsenic from water by TiO2-heterogeneous photocatalysis

Abstract: Fil: Litter, Marta Irene. Universidad Nacional de San Martin. Instituto de Investigacion en Ingenieria Ambiental; Argentina. Comision Nacional de Energia Atomica; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Biofabrication of 3D constructs: fabrication technologies and spider silk proteins as bioinks

Abstract: Abstract Despite significant investment in tissue engineering over the past 20 years, few tissue engineered products have made it to market. One of the reasons is the poor control over the 3D arrangement of the scaffold’s components. Biofabrication is a new field of research that exploits 3D printing technologies with high spatial resolution for the simultaneous processing of cells and biomaterials into 3D constructs suitable for tissue engineering. Cell-encapsulating biomaterials used in 3D bioprinting are referred to as bioinks. This review consists of: (1) an introduction of biofabrication, (2) an introduction of 3D bioprinting, (3) the requirements of bioinks, (4) existing bioinks, and (5) a specific example of a recombinant spider silk bioink. The recombinant spider silk bioink will be used as an example because its unmodified hydrogel format fits the basic requirements of bioinks: to be printable and at the same time cytocompatible. The bioink exhibited both cytocompatible (self-assembly, high cell viability) and printable (injectable, shear-thinning, high shape fidelity) qualities. Although improvements can be made, it is clear from this system that, with the appropriate bioink, many of the existing faults in tissue-like structures produced by 3D bioprinting can be minimized.

Highly efficient electroluminescence from purely organic donor–acceptor systems

Abstract: Abstract Thermally activated delayed fluorescence (TADF) emitters are third-generation electroluminescent materials that realize highly efficient organic light-emitting diodes (OLEDs) without using rare metals. Here, after briefly reviewing the principles of TADF and its use in OLEDs, we report a sky-blue TADF emitter, 9-(4-(benzo[d]thiazol-2-yl)phenyl)-N3,N3,N6,N6-tetraphenyl-9H-carbazole-3,6-diamine (DAC-BTZ). DAC-BTZ is a purely organic donor–acceptor-type molecule with a small energy difference between its lowest excited singlet state and lowest triplet state of 0.18–0.22 eV according to fluorescence and phosphorescence spectra of a DAC-BTZ-doped film. In addition, the doped film exhibits a high photoluminescence quantum yield of 0.82. Time-resolved photoluminescence measurements of the doped film confirm that DAC-BTZ emits TADF. An OLED containing DAC-BTZ as an emitter exhibits a maximum external quantum efficiency (EQE) of 10.3%, which exceeds those obtained with conventional fluorescent emitters (5–7.5%). TADF from DAC-BTZ makes a large contribution to the high EQE of its OLED.

Mechanistic insights from mass spectrometry: examination of the elementary steps of catalytic reactions in the gas phase

Abstract: Abstract Real-time mass spectrometric monitoring of speciation in a catalytic reaction while it is occurring provides powerful insights into mechanistic aspects of the reaction, but cannot be expected to elucidate all details. However, mass spectrometers are not limited just to analysis: they can serve as reaction vessels in their own right, and given their powers of separation and activation in the gas phase, they are also capable of generating and isolating reactive intermediates. We can use these capabilities to help fill in our overall understanding of the catalytic cycle by examining the elementary steps that make it up. This article provides examples of how these simple reactions have been examined in the gas phase.

The eternal youth of azobenzene: new photoactive molecular and supramolecular devices

Abstract: The development of multicomponent chemical systems that can perform predetermined functions under external control - i.e., molecular devices - is a challenging task in chemistry and a fascinating objec- tive in the frame of a bottom-up approach to nanostructures. Photochromic units undergo profound changes in their chemical and/or electronic structure upon light excitation, and are highly interesting for the con- struction of photocontrollable molecular devices, machines and materials. The E-Z photoisomerization of azobenzene - owing to its high efficiency, excellent reversibility and significant physico-chemical differences between the two forms - is a highly useful reaction in this regard. Azobenzene photoisomerization has been known for almost 80 years and has been exploited to implement light-induced functionalities with a large variety of compounds, biomolecules, nanosystems and materials. Here we present some of our recent investi- gations highlighting how this outstanding photochrome can be utilized to develop (supra)molecular systems with valuable light-induced functionalities.

Water–surface interactions and definitions for hydrophilicity, hydrophobicity and superhydrophobicity

Abstract: Abstract Hydrophilicity and hydrophobicity are among the most important concepts in surface chemistry. Samuel and co-workers reported the measure of interactive forces between water and 20 different surfaces using the microbalance technique. Results showed that the wetting force correlates well to the advancing contact angle (θA), the larger the θA the lower the surface wettability. The adhesion force, measured when the water and surface first separates, correlates well to the receding contact angle (θR), the larger the θR the smaller the surface adhesion. The data also reveals that small residual water droplets are observed after the water droplet and the surface separate for surfaces with θR < 90°. This indicates high water affinity for these surfaces. No residual water droplet is observed for surfaces with θR > 90°. From the basic meaning of philicity-phobicity, θR∼90° is proposed as the new cut-off between hydrophilicity and hydrophobicity. The main driver for hydrophobicity is attributed to the high water surface tension. The merit of this proposed definition is discussed. Since wetting interaction becomes zero at θA ≥ 145°, surfaces with θR > 90° and θA ≥ 145° can further be defined as superhydrophobic. The extension of this approach to define oleophilicity/phobicity and superoleophobicity with hexadecane is discussed.

Lipase-catalyzed synthesis of oligoesters of 2,5-furandicarboxylic acid with aliphatic diols

Abstract: 2,5-Furandicarboxylic acid is a platform chemical for the production of biobased polymers and materials. This study reports the synthesis of furan oligoesters via polytransesterification of dimethyl furan-2,5-dicarboxylate and linear α, ω-aliphatic diols with chain length ranging from C2 to C12, using immobilized lipase B from Candida antarctica (Novozym 435) in dry organic solvents. Dimethyl furan-2,5-dicarboxylic acid (A) and 1,4-butanediol (B) were used as model substrates under different conditions producing a mixture of cyclic (CEOs) and linear (LEOs) ester oligomers up to decamers and dodecamers, respectively, with high yield. The size of the oligomers and distribution of the products is controlled by the initial concentration of substrates and temperature. While the shortest CEOs are the main cyclic compounds at 20 mM, the longest CEOs are formed at 175 mM. The chain length of the aliphatic diol co-monomers strongly influences the yield and the type of oligoesters formed. High substrate conversion of 90-95% was obtained for C4-C12 diols, while in the case of ethylene glycol and 1,3-propanediol the conversion was moderate (i.e., 75%). The product of the reaction between dimethyl furan-2,5-dicarboxylate and ethylene glycol (C2) and 1,3-propanediol (C3), respectively, consisted only of linear oligoesters. Longer oligoesters were obtained for alkyl chains higher than C4. The chain length and the abundance of oligoesters increases in the order: C2

Brief guide to the nomenclature of inorganic chemistry

Abstract: INTRODUCCION La adopcion universal de una nomenclatura quimica consensuada es una herramienta clave para la comunicacion eficiente en las ciencias quimicas, para la busqueda con ordenadores en bases de datos y con fines regulatorios, tales como los asociados a la salud y la seguridad o a la actividad comercial. La Union Internacional de Quimica Pura y Aplicada (IUPAC en sus siglas inglesas) ofrece recomendaciones sobre la naturaleza y el uso de la nomenclatura quimica. Los fundamentos de esta nomenclatura se muestran aqui y en los documentos complementarios sobre los sistemas de nomenclatura de quimica organica y polimeros, con hipervinculos a los documentos originales. Un resumen general de la nomenclatura quimica se puede encontrar en Principles of Chemical Nomenclature. Detalles mayores se pueden hallar en Nomenclature of Inorganic Chemistry coloquialmente conocido como el Libro Rojo, y en las publicaciones relacionadas con compuestos organicos (el Libro Azul) y polimeros (el Libro Purpura). Cabe senalar que muchos compuestos pueden tener nombres no-sistematicos o semi-sistematicos (algunos de los cuales no son aceptados por la IUPAC, por ejemplo, porque son ambiguos) y las reglas IUPAC permiten dar mas de un nombre sistematico a un compuesto en muchos casos. La IUPAC esta elaborando la identificacion de los nombres individuales preferidos a efectos de regulacion (Preferred IUPAC Names o PINs). Nota: En este documento, el simbolo ‘=’ se utiliza para dividir los nombres que resultan ser demasiado largos para el formato de la columna, a menos que ya haya un guion presente en el nombre. Los limites entre compuestos ‘organicos’ e ‘inorganicos’ son difusos. Los tipos de nomenclatura descritos en este documento son aplicables a los compuestos, moleculas e iones que no contienen carbono y tambien a muchas estructuras que contienen carbono (Seccion 2), principalmente los que contienen elementos de los grupos 1−12. La mayoria de los compuestos de boro se tratan mediante una nomenclatura especial. 8

Self-trapping of charge polarized states in four-dot molecular quantum cellular automata: bi-electronic tetrameric mixed-valence species

Abstract: Abstract Our interest in this article is prompted by the problem of the vibronic self-trapping of charge polarized states in the four-dot molecular quantum cellular automata (mQCA), a paradigm for nanoelectronics, in which binary information is encoded in charge configuration of the mQCA cell. We report the evaluation of the electronic states and the adiabatic potentials of mixed-valence (MV) systems in which two electrons (or holes) are shared among four sites. These systems are exemplified by the two kinds of tetra–ruthenium (2Ru(II)+ 2Ru(III)) clusters (assembled as two coupled Creutz–Taube dimers) for which molecular implementation of mQCA was proposed. The tetra–ruthenium clusters include two holes shared among four sites and correspondingly we employ the model which takes into account the electron transfer processes as well as the Coulomb repulsion in the different instant positions of localization. The vibronic self-trapping is considered within the conventional vibronic Piepho, Krausz and Schatz (PKS) model adapted to the bi-electronic MV species with the square topology. This leads to a complicated vibronic problems (21A1g + 1B1g + 1B2g + 1Eu) ⊗ (b1g + eu) and (3A2g + 3B1g + 23Eu) ⊗ (b1g + eu) for spin-singlet and spin-triplet states correspondingly. The adiabatic potentials are evaluated with account for the low lying Coulomb levels in which the antipodal sites are occupied, the case just actual for utilization in mQCA. The conditions for the vibronic localization in spin-singlet and spin-triplet states are revealed in terms of the two actual transfer pathways parameters and strength of the vibronic coupling.

Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)

Abstract: This document defines terms relating to the properties of individual macromolecules, macromo­ lecular assemblies, polymer solutions, and amorphous bulk polymers. In the section on polymer solutions and amorphous bulk polymers, general and thermodynamic terms, dilute solutions, phase behaviour, trans­ port properties, scattering methods, and separation methods are considered. The recommendations are a revision and expansion of the IUPAC terminology published in 1989 dealing with individual macromolecules, macromolecular assemblies, and dilute polymer solutions. New terms covering the principal theoretical and experimental developments that have occurred over the intervening years have been introduced. Polyelectro­ lytes are not included.

Electrical properties of hydroxyapatite

Abstract: Abstract Despite being one of the mostly studied biomaterials for orthopedic, dental, protein purification and stem cell applications, electrical properties of hydroxyapatite has received only limited attention. Since the prediction in 2005 of the possibility of piezo and pyroelectricity in hydroxyapatite several theoretical and experimental works in this field may lead to new understandings of electrical behaviors of calcified tissues in vertebrates. Also, the ability of creating discrete electrostatic domains on nanocrystalline films of hydroxyapatite will open the possibility of understanding how surface charge influences biological interactions. The outlook for future endeavours in this field will be discussed.

Discovery and development of photochromic diarylethenes

Abstract: Abstract A new family of thermally irreversible photochromic molecules, named “diarylethene,” was serendipitously discovered a quarter of a century ago. The diarylethenes undergo thermally irreversible, fatigue resistant, ultrafast and highly sensitive photochromic reactions. Many of diarylethenes can undergo photochromic reactions even in the single-crystalline phase. The outstanding photochromic performance attracts considerable attention from both scientific and technological points of view, and stimulates research from fundamental physico-chemical aspects to various applications. Here, it is reported how such thermally irreversible photochromic diarylethenes were discovered and developed.

What we know and still not know about oceanic salts

Abstract: Abstract The term oceanic salts concerns the salts, which can be formed from solutions containing the major ions of seawater, that is the hexary system Na+, K+, Mg++, Ca++, Cl–, SO4––H2O. Besides in geochemistry of evaporites and the potash extraction the solubility equilibria and properties of aqueous solutions containing these ions are of importance in many fields of science and technology in a wide range of temperature and composition. After a short introduction into the types of subsystems and the main features of their solubility diagrams the known salt phases, their properties and stability are listed and discussed with a focus on recent work and discoveries. The status of solubility data evaluation of the multi-component system is discussed from the view point of the data itself and the possibilities and limitations of applying thermodynamic modelling. This is demonstrated with the data compilation of Usdowski and Dietzel, the Pitzer models of Harvie, Möller and Weare as well as the model developed in the THEREDA project. Future work should be directed to improve accuracy of solubility data in multi-component solutions combined with modelling and to consider kinetics and mechanistic aspects in crystallization of phases like anhydrite or polyhalite.

Building blocks for bioinspired electrets: molecular-level approach to materials for energy and electronics

Abstract: Author(s): Larsen, JM; Espinoza, EM; Hartman, JD; Lin, CK; Wurch, M; Maheshwari, P; Kaushal, RK; Marsella, MJ; Beran, GJO; Vullev, VI | Abstract: In biology, an immense diversity of protein structural and functional motifs originates from only 20 common proteinogenic native amino acids arranged in various sequences. Is it possible to attain the same diversity in electronic materials based on organic macromolecules composed of non-native residues with different characteristics? This publication describes the design, preparation and characterization of non-native aromatic β-amino acid residues, i.e. derivatives of anthranilic acid, for polyamides that can efficiently mediate hole transfer. Chemical derivatization with three types of substituents at two positions of the aromatic ring allows for adjusting the energy levels of the frontier orbitals of the anthranilamide residues over a range of about one electronvolt. Most importantly, the anthranilamide residues possess permanent electric dipoles, adding to the electronic properties of the bioinspired conjugates they compose, making them molecular electrets.

Simulation of sunscreen performance

Abstract: Abstract Sunscreens are used to protect the human skin against harmful effects of solar UV radiation. The most important quantity characterizing sunscreen performance is the sun protection factor (SPF). At the stage of development of new sun protection formulations quick and inexpensive methods for estimation of the UV screening performance are highly desirable. The most convenient approach towards this goal is given by computational simulations. Models for the calculation of the SPF employ the same algorithm as used with in vitro SPF measurements, but replace the transmittance measurement by the calculation of the overall absorbance of the UV filters in an irregular sunscreen film. The simulations require a database with quantitative UV extinction spectra of the relevant UV filters as well as a mathematical description of the film irregularity. The simulation algorithm implies also the consideration of photodegradation properties of the UV filters in the sunscreen composition. Besides using such simulations for designing new sunscreen formulations, the calculations can also support the understanding of sunscreen performance in general.

Photochemistry and photophysics of mycosporine-like amino acids and gadusols, nature’s ultraviolet screens

Abstract: Mycosporine-like amino acids (MAAs) and related gadusols are among the most prominent examples of metabolites suggested to act as UV-sunscreens. This review illustrates how experimental and theoretical studies on model MAAs and gadusol offer a helpful description of the photoprotective mechanism at the molecular level. This knowledge may contribute to the rational design of chemical systems with predictable and tuneable response to light stimulus. Synthetic efforts to obtain MAAs and simplified related structures are also discussed. © IUPAC & De Gruyter 2015.

Amino acid sequence controls the self-assembled superstructure morphology of N-acetylated tri-β3-peptides

Abstract: Abstract Peptides based on unnatural β3-amino acids offer a versatile platform for the design of self-assembling nanostructures due to the folding stability of the 14-helix and the high symmetry of the side chains inherent in this geometry. We have previously described that N-terminal acetylation (Ac-) forms a supramolecular self-assembly motif that allows β3-peptides to assemble head-to-tail into a helical nanorod which then further bundles into hierarchical superstructures. Here we investigate the effect of the topography of the 14-helical nanorod on lateral self-assembly. Specifically, we report on the variations in the superstructure of three isomeric peptides comprising the same three β3-amino acid residues: β3-leucine (L), β3-isoleucine (I) β3-alanine (A) to give peptides Ac-β3[LIA], Ac-β3[IAL] and Ac-β3[ALI]. AFM imaging shows markedly different superstructures for the three peptides. Well defined synchrotron far-infrared spectra reveal uniform geometries with a high degree of similarity between the isomeric peptides in the amide modes of the 400–650 wavenumber range. Far-IR also confirms that the C-terminal carboxyl group is free in the assemblies, thus it is solvated in the dispersant. Hence, the differences in the superstructures formed by the fibers are defined primarily by van der Waals energy minimization between the varied cross sectional morphologies of the core nanorods.

Photophysical, electrochemical, and spectroelectrochemical investigation of electronic push–pull benzothiadiazole fluorophores

Abstract: Abstract Two electronic push–pull fluorophores consisting of a benzothiadiazole core and a terminal N,N-dimethylamino electron donating group were prepared. The effect of the terminal electron withdrawing group (–NO2 and –CN) on the spectroscopic, electrochemical, and spectroelectrochemical properties were examined. The fluorophores were solvatochromic with Stokes shifts upward of 9000 cm−1 being observed in aprotic solvents of varying polarity. It was found that the fluorophores fluoresced appreciably (86 % > Φfl > 18 %) in hexane, toluene, diethyl ether, dichloromethane, ethyl acetate, and THF. The fluorescence was quenched in acetonitrile, acetone, and DMSO. The fluorophores also fluoresced appreciably in thin films when embedded in poly(methyl methacrylate) and poly(dimethylsiloxane) matrices. Protonating the terminal amine with trifluoroacetic acid quenched the intramolecular charge transfer band, although the fluorophores remained fluorescent. The fluorophores could also be reversibly oxidized electrochemically. The resulting oxidized state was visually different than the neutral form. Electrochemical oxidation also led to reversible changes in both the fluorescence wavelength and intensity.

Carbaboranes – more than just phenyl mimetics

Abstract: Abstract Dicarba-closo-dodecaboranes(12) (C2B10H12, carbaboranes) are highly hydrophobic and stable icosahedral carbon-containing boron clusters. The cage framework of these clusters can be modified with a variety of substituents, both at the carbon and at the boron atoms. Substituted carbaboranes are of interest in medicine as boron neutron capture therapy (BNCT) agents or as pharmacophores. High and selective accumulation in tumour cells is an important requirement for a BNCT agent and is achieved by incorporating boron-rich, water-soluble carbaborane derivatives into breast tumour-selective modified neuropeptide Y, [F7, P34]-NPY. Preliminary studies showed that the receptor binding affinity and signal transduction of the boron-modified peptides were very well retained. Use of carbaboranes as pharmacophores was shown by replacement of Bpa32 (Bpa=benzoylphenylalanine) in the reduced-size NPY analogue [Pro30, Nle31, Bpa32, Leu34]-NPY 28–36 by ortho-carbaboranyl propanoic acid. The inclusion of the carbaborane derivative resulted in a short NPY agonist with an interesting hY2R/hY4R preference. This might be a promising approach in the field of anti-obesity drug development.

Viscosity of Se–Te glass-forming system

Abstract: Abstract This work is focused on viscosity of chalcogenide system Se–Te. Viscosity values of four glass-forming compositions in this system (containing 5, 10, 20 and 30 at.% of tellurium) were measured by penetration and parallel-plate method in the region of undercooled melt and glass. These results are combined with literature data for melt region. The kinetic fragility and viscosity glass transition temperature values obtained by different methods are calculated from measured data.

Boric acid: a simple molecule of physiologic, therapeutic and prebiotic significance

Abstract: : Boric acid, H 3 BO 3 , is a weak acid and at physiological pH is in the form of an uncharged small molecule. Behaving as a Lewis acid, it forms complexes with amino- and hydroxy acids, carbohydrates, nucleotides and vitamins through electron donor-acceptor interactions. These interactions are believed to be beneficial for human health. Synthetic bis- chelate complexes of boric acid with organic biomolecules are therefore considered for nutritional and/or pharmaceutical applications. The use of boric acid for BNCT has gained attention due to the short biological half-life, solubility, plasma circulation and the non-selective soft tissue accumulation properties of this simple molecule. Complexation of boric acid with sugars is of particular importance in understanding the role of boron as a carrier for nucleotides and carbohydrates. A potential and catalytic role of boric acid in peptide and nucleic acid synthesis and in the stabilization of sugar molecules by acting as a complexing agent have been demonstrated. Its possible role as a phosphorylation chaperone in a prebiotic world has been recently suggested. This contribution reviews the highlights in the physiologic, therapeutic and prebiotic significance of boric acid in the last decade. Keywords: boric acid; borate ester; borate complex; prebiotic chemistry.

Selectivity of lipases for estolides synthesis

Abstract: Lipase-catalyzed synthesis of estolides starting from different saturated (C16 16OH, C18 12OH) and unsaturated (C18:1 9 cis 12-OH) hydroxy-fatty acids was investigated. For this reason, the catalytic efficiency of several native and immobilized lipases in different organic reaction media at temperatures up to 75 °C was studied. The formation of mono- and di-lactone as well as estolide’s chain elongation depends on the type and source of lipase. The lipase from Pseudomonas stutzeri immobilized by cross-linking as cross-linked enzymes aggregates (CLEAs) was the best biocatalyst in terms of chain elongation. Estolides with polymerization degree up to 10 were obtained at substrate conversions higher than 80 %.

Gas-phase studies of metal catalyzed decarboxylative cross-coupling reactions of esters

Abstract: Metal-catalyzed decarboxylative coupling reactions of esters offer new opportunities for formation of C-C bonds with CO2 as the only coproduct. Here I provide an overview of: key solution phase literature; thermochemical considerations for decarboxylation of esters and thermolysis of esters in the absence of a metal catalyst. Results from my laboratory on the use of multistage ion trap mass spectrometry experiments and DFT calculations to probe the gas-phase metal catalyzed decarboxylative cross-coupling reactions of allyl acetate and related esters are then reviewed. These studies have explored the role of the metal carboxylate complex in the gas phase decarboxylative coupling of allyl acetate proceeding via a simple two-step catalytic cycle. In Step 1, an organometallic ion, [CH3ML]+/- (where M is a group 10 or 11 metal and L is an auxillary ligand), is allowed to undergo ion-molecule reactions with allyl acetate to generate 1-butene and the metal acetate ion, [CH3CO2ML]+/-. In Step 2, the metal acetate ion is subjected to collision-induced dissociation to reform the organometallic ion and thereby close the catalytic cycle. DFT calculations have been used to explore the mechanisms of these reactions. The organometallic ions [CH3CuCH3]-, [CH3Cu2]+, [CH3AgCu]+ and [CH3M(phen)]+ (where M = Ni, Pd and Pt) all undergo C-C bond coupling reactions with allyl acetate (Step 1), although the reaction efficiencies and product branching ratios are highly dependant on the nature of the metal complex. For example, [CH3Ag2]+ does not undergo C-C bond coupling. Using DFT calculations, a diverse range of mechanisms have been explored for these C-C bond-coupling reactions including: oxidative-addition, followed by reductive elimination; insertion reactions and SN2-like reactions. Which of these mechanisms operate is dependant on the nature of the metal complex. A wide range of organometallic ions can be formed via decarboxylation (Step 2) although these reactions can be in competition with other fragmentation channels. DFT calculations have located different types of transition states for the formation of [CH3CuCH3]-, [CH3Cu2]+, [CH3AgCu]+ and [CH3M(phen)]+ (where M = Ni, Pd and Pt). Of the catalysts studied to date, [CH3Cu2]+ and [CH3Pd(phen)]+ are best at promoting C-C bond formation (Step 1) as well as being regenerated (Step 2). Preliminary results on the reactions of [C6H5M(phen)]+ (M = Ni and Pd) with C6H5CO2CH2CH=CH2 and C6H5CO2CH2C6H5 are described.

Thermodynamic properties of molybdate ion: reaction cycles and experiments

Abstract: Abstract Standard molar quantities of molybdate ion entropy, Sm0,$S_{\\rm{m}}^0,$ enthalpy of formation, ΔfHmo,${\\Delta _{\\rm{f}}}H_m^{\\rm{o}},$ and Gibbs energy of formation, ΔfGmo,${\\Delta _{\\rm{f}}}G_{\\rm{m}}^{\\rm{o}},$ are key data for the thermodynamic properties of molybdenum compounds and complexes, which are at present investigated by an OECD NEA review project. The most reliable method to determine ΔfHmo${\\Delta _{\\rm{f}}}H_{\\rm{m}}^{\\rm{o}}$ of molybdate ion and alkali molybdates directly consists in measuring calorimetrically the enthalpy of dissolution of crystallized molybdenum trioxide and anhydrous alkali molybdates in corresponding aqueous alkali metal hydroxide solutions. Solubility equilibria of sparingly soluble alkaline earth molybdates and silver molybdate lead to trustworthy data for ΔfGmo${\\Delta _{\\rm{f}}}G_{\\rm{m}}^{\\rm{o}}$ of molybdate ion. Thereby the Gibbs energies of the metal molybdates and the corresponding metal ions are combined with the Gibbs energies of dissolution. As reliable values are available for ΔfGmo${\\Delta _{\\rm{f}}}G_{\\rm{m}}^{\\rm{o}}$ of the relevant metal ions the problem reduces to select the best values of solubility constants and ΔfGmo${\\Delta _{\\rm{f}}}G_{\\rm{m}}^{\\rm{o}}$ of alkaline earth molybdates and silver molybdate. There are two independent possibilities to achieve the latter task. (1) ΔfHmo${\\Delta _{\\rm{f}}}H_{\\rm{m}}^{\\rm{o}}$ for alkaline earth molybdates and silver molybdate have been determined by solution calorimetry. Entropy data of molybdenum have been compiled and evaluated recently. CODATA key values are available for Smo$S_{\\rm{m}}^{\\rm{o}}$ of the other elements involved. Whereas Smo(CaMoO4, cr)$S_{\\rm{m}}^{\\rm{o}}({\\rm{CaMo}}{{\\rm{O}}_4},{\\rm{ cr}})$ is well known since decades, low-temperature heat capacity measurements had to be performed recently, but now reliable values for Smo$S_{\\rm{m}}^{\\rm{o}}$ of Ag2MoO4(cr), BaMoO4(cr) and SrMoO4(cr) are available. (2) ΔfHmo(BaMoO4, cr),${\\Delta _{\\rm{f}}}H_{\\rm{m}}^{\\rm{o}}({\\rm{BaMo}}{{\\rm{O}}_4},{\\rm{ cr}}),$ for example, can be obtained from high temperature equilibria also, but the result is less accurate than that of the first method. Once Gibbs energy of formation, ΔfGmo,${\\Delta _{\\rm{f}}}G_{\\rm{m}}^{\\rm{o}},$ and enthalpy of formation, ΔfHmo,${\\Delta _{\\rm{f}}}H_{\\rm{m}}^{\\rm{o}},$ of molybdate ion are known its standard entropy, Smo,$S_{\\rm{m}}^{\\rm{o}},$ can be calculated.

Winners of the 2014 IUPAC-SOLVAY International Award for Young Chemists

Abstract: Since the year 2000, IUPAC has been honoring young, outstanding, early career research scientists by making annual awards for the most outstanding PhD theses in the area of the chemical sciences. The awards have been based on 1000-word essays on their research. We are delighted to welcome Solvay into this initiative. Solvay, created in 1863, is firmly committed to sustainable development focused on innovation and operating excellence, and also to the development of science and technology, particularly concerning the new generations of young scientists. The 2014 IUPAC-SOLVAY International Award for Young Chemists is the first with their sponsorship, but follows the IUPAC tradition in this area. The prize selection committee of eminent chemists was keen to recognize a global representation of the awards, and enjoyed 55 high-quality applications submitted by candidates from 20 countries. After critical consideration of the research results and evaluation of the originality and excellence of the presentations, they decided unanimously to award the 2014 prizes to the following five essays: – “(1) Ligand-accelerated catalysis in palladium(II)-mediated C–H functionalization; and (2) Hydrogenbonding effects on the reactivity of fluoride anion”, Keary Mark Engle, The Scripps Research Institute, La Jolla, CA, USA, joint with University of Oxford, UK. – “Molecular switches based on donor–acceptor, radical and coulombic interactions: From solution, to solid-state to application”, Albert C. Fahrenbach, Northwestern University, Evanston, IL, USA. – “Artificial light-harvesting system by supramolecular host–guest assemblies”, Yohei Ishida, Tokyo Metropolitan University, Japan. – “Selective metal-mediated C–C bond activation of strain compounds: Application to challenging non-natural product synthesis”, Ahmad Masarwa, Technion-Israel Institute of Technology, Haifa, Israel. – “Anion transport with anion-π interactions and halogen bonds” Rodrigo Andreas Vargas Jentzsch, University of Geneva, Switzerland.

The potential of polymers from natural sources as components of the blends for biomedical and cosmetic applications

Abstract: Abstract A short overview of recent advances in studies of the interactions between natural polymers and application of polymers from natural sources as components of the blends for biomedical and cosmetic applications is presented. This work is focused on the blends of collagen, chitosan, silk fibroin and keratin. These bioinspired and biobased materials can be good alternative for materials based on synthetic polymers. The case study of the blends made of collagen and keratin hydrolysate is presented.