The X<Superscript>−</Superscript>···benzohydrazide complexes: the interplay between anion-π and H-bond interactions

The compounds containing the benzohydrazide (BH) nucleus have a variety of biological activities because of various noncovalent intermolecular interactions. The interplay between anion-π and H-bond interactions, which can affect the activity of compounds, has been investigated in ten substituted BH exposed to the chloride ion using the quantum mechanical calculations. The total interaction energy is separated into the anion-π (ΔE _Aπ) and H-bond (ΔE _HB) contributions where both interactions are presented in the complexes. The electron-withdrawing substituents (EWSs) increase |ΔE _Aπ| and decrease |ΔE _HB|, while reversed changes are observed with the electron-donating substituents (EDSs). In addition, the total binding energy (ΔE) becomes more/less negative in the presence of EWSs/EDSs. The synergetic effects of mentioned interactions and substituent effects have also been investigated using the atoms in molecules (AIM), natural bond orbital (NBO) and molecular electrostatic potential (MEP) analyses. A good correlation is found between the energy data and the Hammett constants, the minimum of electrostatic potential (V _min) and the results of population analyses.     

DFT studies on the acid-catalyzed Curtius reaction: the Schmidt reaction

The Schmidt reaction is the acid-catalyzed analogue of the Curtius reaction and is extensively used in organic synthesis. In this work, the mechanism of this reaction has been explored using DFT calculations at the B3LYP/6-311+G(d,p) level. Protonated formyl azide may undergo rearrangement to the product, protonated isocyanic acid, with simultaneous extrusion of molecular nitrogen (concerted mechanism), or undergo rearrangement to the anti conformer, followed by removal of nitrogen to form the nitrenium ion, which then rearranges to the final product, protonated isocyanic acid (step-wise mechanism). Like the Curtius reaction, it is found that the concerted pathway is definitely preferred. The key role of acidification in decreasing the overall energy barrier is more highlighted in case of phenyl substitution, with negligible effect on the lower homologues. For methoxy and amine substituents, there is very little difference in the activation energies of the concerted and step-wise reactions, with the former being still slightly preferred. Unlike the parent compound, the rearrangement of substituted nitrenium ion in some cases involves side reactions like C-H insertion and cyclization.     

Are metals made from molecules?

In the traditional view, covalently bound materials differ in a fundamental way from metallic substances. Though both are built from more basic units that are, in turn, constructed from a small number of atoms, for these two materials classes the nature of these units is thought to be quite different. For covalent solids and liquids, these units are considered to be molecular, meaning that they possess properties and bonding that are retained in the condensed phase and thus they continue to be identifiable within the larger system. For metallic materials, these basic units are considered to be mere constructs that are not observable against the delocalized bonding of metals or alloys. The perceived dissimilarity of metallic and covalently bound materials has fostered distinctly different approaches to their design and improvement. Here, the delocalized view of metallic bonding is examined. This examination suggests that much of the rationale used in the design of molecular materials my be applied to metals and alloys as well.     

Hydrothermal Syntheses and Crystal Structure of a New Organic Hybrid Holmium–Germanate Oxo-Cluster

A new organic hybrid holmium–germanate oxo-cluster [Ho₈(phen)₂Ge₁₂(μ ₃-O)₂₄(CH₂CH₂COO)₁₂(H₂O)₁₆]·2H₂O (1, phen = 1,10-phenanthroline) was prepared under mild hydrothermal conditions and structurally characterized by elemental analysis, UV/Vis, IR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Compounds 1 contains cage clusters [Ho₈(phen)₂Ge₁₂(μ ₃-O)₂₄(CH₂CH₂COO)₁₂(H₂O)₁₆] and free H₂O molecules. The cage cluster is constructed by the combination of two [Ho(phen)(H₂O)₂] units, two [Ge₆O₁₂(CH₂CH₂COO)₆] rings and one circular [Ho₆O₃₆] fragment via sharing O atoms. 1 is the rare example of organic hybrid holmium–germanate oxo-cluster decorated by phen ligands.     

The First Organic–Inorganic Hybrid Compound Based on Polyoxotungstates and Alkali-tris(imidazolyl) Segments with Electrocatalytic Activity

The first organic–inorganic hybrid compound based on the Keggin polyoxometalate and alkali-N-heterocycle ligand [Na₄(tib)₂(H₂O)₂(α-HBW₁₂O₄₀)]·2H₂O (1) (tib = 1,3,5-tris(1-imidazoly)benzene) was hydrothermally synthesized by utilizing a pH-dependent approach in the POM/Cu/tib reaction systems. X-ray structural analyses reveal that compound 1, formed in pH 5.2, possesses a (3,4,6)-connected 2D net with the (4²·5)(4⁶)(3³·4⁶·5²·6⁴) topology. In addition, electrochemical and electrocatalytic properties of compound 1 were studied by cyclic voltammograms. Compound 1 displayed electrocatalytic activities toward reduction of nitrite.     

Maximizing Ion Transmission in Differential Mobility Spectrometry

We provide modeling and experimental data describing the dominant ion-loss mechanisms for differential mobility spectrometry (DMS). Ion motion is considered from the inlet region of the mobility analyzer to the DMS exit, and losses resulting from diffusion to electrode surfaces, insufficient effective gap, ion fragmentation, and fringing field effects are considered for a commercial DMS system with 1-mm gap height. It is shown that losses due to diffusion and radial oscillations can be minimized with careful consideration of residence time, electrode spacing, gas flow rate, and waveform frequency. Fragmentation effects can be minimized by limitation of the separation field. When these parameters were optimized, fringing field effects at the DMS inlet contributed the most to signal reduction. We also describe a new DMS cell configuration that improves the gas dynamics at the mobility cell inlet. The new cell provides a gas jet that decreases the residence time for ions within the fringing field region, resulting in at least twofold increase in ion signal as determined by experimental data and simulations.

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Quantitative Proteomic Analysis of Optimal Cutting Temperature (OCT) Embedded Core-Needle Biopsy of Lung Cancer

With recent advances in understanding the genomic underpinnings and oncogenic drivers of pathogenesis in different subtypes, it is increasingly clear that proper pretreatment diagnostics are essential for the choice of appropriate treatment options for non-small cell lung cancer (NSCLC). Tumor tissue preservation in optimal cutting temperature (OCT) compound is commonly used in the surgical suite. However, proteins recovered from OCT-embedded specimens pose a challenge for LC-MS/MS experiments, due to the large amounts of polymers present in OCT. Here we present a simple workflow for whole proteome analysis of OCT-embedded NSCLC tissue samples, which involves a simple trichloroacetic acid precipitation step. Comparisons of protein recovery between frozen versus OCT-embedded tissue showed excellent consistency with more than 9200 proteins identified. Using an isobaric labeling strategy, we quantified more than 5400 proteins in tumor versus normal OCT-embedded core needle biopsy samples. Gene ontology analysis indicated that a number of proliferative as well as squamous cell carcinoma (SqCC) marker proteins were overexpressed in the tumor, consistent with the patient’s pathology based diagnosis of “poorly differentiated SqCC”. Among the most downregulated proteins in the tumor sample, we noted a number of proteins with potential immunomodulatory functions. Finally, interrogation of the aberrantly expressed proteins using a candidate approach and cross-referencing with publicly available databases led to the identification of potential druggable targets in DNA replication and DNA damage repair pathways. We conclude that our approach allows LC-MS/MS proteomic analyses on OCT-embedded lung cancer specimens, opening the way to bring powerful proteomics into the clinic.

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