On ‐Cocyclic Hadamard Matrices

In this paper, we describe some necessary and sufficient conditions for a set of coboundaries to yield a cocyclic Hadamard matrix over the dihedral group . Using this characterization, new classification results for certain cohomology classes of cocycles over are obtained, extending existing exhaustive calculations for cocyclic Hadamard matrices over from order 36 to order 44. We also define some transformations over coboundaries, which preserve orthogonality of ‐cocycles. These transformations are shown to correspond to Horadam's bundle equivalence operations enriched with duals of cocycles.     

Multielement analysis of lichen samples using XRF methods. Comparison with ICP‐AES and FAAS

This research presents the contents of Ca, Fe, Zn, Br, Rb, Sr and Pb in lichen samples used as biomonitors of air pollution collected in Havana. Statistical comparisons were made among the results obtained in three campaigns during three years. Two X‐Ray Fluorescence (XRF) methods were used, employing for excitation an annular ¹⁰⁹Cd source and a Mo X‐ray tube with a molybdenum secondary target. In both cases, matrix effects were corrected by the use of normalization for the Compton scattered peak; in this way the determination is more efficient. For quality control of the results, biological Certified Reference Materials were analyzed and were made comparisons between XRF, Inductively Coupled Plasma‐Atomic Emission Spectrometry and Flame Atomic Absorption Spectrophotometry. No significant differences were found between the different techniques. The elemental distribution patterns obtained for each metal were associated with different pollution sources, thus contributing to the assessment of air pollution in Havana. Copyright © 2015 John Wiley & Sons, Ltd.     

A One‐Pot Cascade Reaction Combining an Encapsulated Decarboxylase with a Metathesis Catalyst for the Synthesis of Bio‐Based Antioxidants

The combination of enzymes with traditional chemical catalysts unifies the high selectivity of the former with the versatility of the latter. A major challenge of this approach is the difference in the optimal reaction conditions for each catalyst type. In this work, we combined a cofactor‐free decarboxylase with a ruthenium metathesis catalyst to produce high‐value antioxidants from bio‐based precursors. As suitable ruthenium catalysts did not show satisfactory activity under aqueous conditions, the reaction required the use of an organic solvent, which in turn significantly reduced enzyme activity. Upon encapsulation of the decarboxylase in a cryogel, the decarboxylation could be conducted in an organic solvent, and the recovery of the enzyme after the reaction was facilitated. After an intermediate drying step, the subsequent metathesis in pure organic solvent proved to be straightforward. The synthetic utility of the cascade was demonstrated by the synthesis of the antioxidant 4,4′‐dihydroxystilbene in an overall yield of 90 %.     

Exploiting Deep Eutectic Solvents and Organolithium Reagent Partnerships: Chemoselective Ultrafast Addition to Imines and Quinolines Under Aerobic Ambient Temperature Conditions

Shattering the long‐held dogma that organolithium chemistry needs to be performed under inert atmospheres in toxic organic solvents, chemoselective addition of organolithium reagents to non‐activated imines and quinolines has been accomplished in green, biorenewable deep eutectic solvents (DESs) at room temperature and in the presence of air, establishing a novel and sustainable access to amines. Improving on existing methods, this approach proceeds in the absence of additives; occurs without competitive enolization, reduction or coupling processes; and reactions were completed in seconds. Comparing RLi reactivities in DESs with those observed in pure glycerol or THF suggests a kinetic anionic activation of the alkylating reagents occurs, favoring nucleophilic addition over competitive hydrolysis.     

Aqueous Solutions of Ionic Liquids: Microscopic Assembly

Aqueous solutions of ionic liquids are of special interest, due to the distinctive properties of ionic liquids, in particular, their amphiphilic character. A better understanding of the structure–property relationships of such systems is hence desirable. One of the crucial molecular‐level interactions that influences the macroscopic behavior is hydrogen bonding. In this work, we conduct molecular dynamics simulations to investigate the effects of ionic liquids on the hydrogen‐bond network of water in dilute aqueous solutions of ionic liquids with various combinations of cations and anions. Calculations are performed for imidazolium‐based cations with alkyl chains of different lengths and for a variety of anions, namely, [Br]^?, [NO₃]^?, [SCN]^?, [BF₄]^?, [PF₆]^?, and [Tf₂N]^?. The structure of water and the water–ionic liquid interactions involved in the formation of a heterogeneous network are analyzed by using radial distribution functions and hydrogen‐bond statistics. To this end, we employ the geometric criterion of the hydrogen‐bond definition and it is shown that the structure of water is sensitive to the amount of ionic liquid and to the anion type. In particular, [SCN]^? and [Tf₂N]^? were found to be the most hydrophilic and hydrophobic anions, respectively. Conversely, the cation chain length did not influence the results.     

How Electronic Excitation Can be Used to Inhibit Some Mechanisms Associated to Substituent Effects

Despite the fact that transferability and chemistry go hand in hand, transferability studies in electronically excited states (EESs) are normally omitted, although these states are becoming extremely important in modern processes and applications. In this work, it is shown that this kind of studies can be used to understand how substituent effects can be modified in EESs. Thus, for example, the analysis of the carbonyl oxygen transferability in different HCO‐R molecules allowed us to find that the excitation can be used to break the π conjugation associated to the resonance substituent effect. Moreover, as a direct consequence, the oxygen transferability is enhanced in the first electronically excited state.     

Study of the Chemical Space of Selected Bacteriostatic Sulfonamides from an Information Theory Point of View

The relative structural location of a selected group of 27 sulfonamide‐like molecules in a chemical space defined by three information theory quantities (Shannon entropy, Fisher information, and disequilibrium) is discussed. This group is composed of 15 active bacteriostatic molecules, 11 theoretically designed ones, and para‐aminobenzoic acid. This endeavor allows molecules that share common chemical properties through the molecular backbone, but with significant differences in the identity of the chemical substituents, which might result in bacteriostatic activity, to be structurally classified and characterized. This is performed by quantifying the structural changes on the electron density distribution due to different functional groups and number of electrons. The macroscopic molecular features are described by means of the entropy‐like notions of spatial electronic delocalization, order, and uniformity. Hence, an information theory three‐dimensional space (IT‐3D) emerges that allows molecules with common properties to be gathered. This space witnesses the biological activity of the sulfonamides. Some structural aspects and information theory properties can be associated, as a result of the IT‐3D chemical space, with the bacteriostatic activity of these molecules. Most interesting is that the active bacteriostatic molecules are more similar to para‐aminobenzoic acid than to the theoretically designed analogues.     

Native MS and ECD Characterization of a Fab–Antigen Complex May Facilitate Crystallization for X-ray Diffraction

Native mass spectrometry (MS) and top-down electron-capture dissociation (ECD) combine as a powerful approach for characterizing large proteins and protein assemblies. Here, we report their use to study an antibody Fab (Fab-1)–VEGF complex in its near-native state. Native ESI with analysis by FTICR mass spectrometry confirms that VEGF is a dimer in solution and that its complex with Fab-1 has a binding stoichiometry of 2:2. Applying combinations of collisionally activated dissociation (CAD), ECD, and infrared multiphoton dissociation (IRMPD) allows identification of flexible regions of the complex, potentially serving as a guide for crystallization and X-ray diffraction analysis.

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Benzotrithiophene‐Based Hole‐Transporting Materials for 18.2 % Perovskite Solar Cells

New star‐shaped benzotrithiophene (BTT)‐based hole‐transporting materials (HTM) BTT‐1, BTT‐2 and BTT‐3 have been obtained through a facile synthetic route by crosslinking triarylamine‐based donor groups with a benzotrithiophene (BTT) core. The BTT HTMs were tested on solution‐processed lead trihalide perovskite‐based solar cells. Power conversion efficiencies in the range of 16 % to 18.2 % were achieved under AM 1.5 sun with the three derivatives. These values are comparable to those obtained with today's most commonly used HTM spiro‐OMeTAD, which point them out as promising candidates to be used as readily available and cost‐effective alternatives in perovskite solar cells (PSCs).