A systematic methodology to design silica templates: Silica microemulsion formulation and nanodroplet type and size estimation

A systematic study of the design and characterization of silica-microemulsion templates is presented. The ternary phase diagrams in micro-heterogeneous systems, by using a non-ionic surfactant (Brij 30) and different silica precursors (MTEOS, TEOS, PTEOS), have been drawn. Based on Khalweit diagrams, the phase inversion temperature was estimated as close to 315 K, for both alchil (TEOS) and aril (PTEOS) types of alcoxides. By correlating the information obtained from phase diagrams at room temperature with that of size effects revealed by VIS absorption molecular probes (bromthymol blue dye), the phase inversion point, i.e. the transition point from water-in-oil to oil-in-water microemulsion, was also clearly established as corresponding to R ∼ 1. Besides technically attractive features such as a wide variety of inorganic and hybrid nanomaterials, high specific surface and highly efficient applicative properties of the final materials, the approach of silica-microemulsion-based templates can be seen as a route towards the Green Chemistry concept.     

N → Sn coordination in the complexes of tin halides with pyridine: A comparison between Sn(II) and Sn(IV)

The experimentally well‐known complexation of tin(II) and tin(IV) halides with pyridine (py) leads to structures showing N → Sn coordination. In the present work, the complexes SnX_n·mpy (where X = F, Cl, Br, I; n = 2, 4; m = 1, 2) possessing this kind of coordination were studied using a computational quantum chemical approach. Various aspects in the theoretical picture of these complexes were examined to find similarities and differences in their N → Sn coordination. The aspects included, among others, the physical nature of intermolecular interactions, and their role in establishing the structure and energetic stabilization of the complexes. In this context, the effect of tin valency was inspected in great detail. As proven by several theoretical methods, a largely ionic character with a certain covalent component can be attributed to the studied N → Sn coordination, irrespective of tin valency. All complexes are destabilized by py‐py and three‐body interactions, but the Sn(II) complexes experience it to a greater extent. Marked differences are observed in the structural behavior of N → Sn and SnX_n during complex formation. This affects the energetics of complexation and, in consequence, the penta‐coordinated Sn(IV) center shows a higher propensity to expand its coordination number, compared with the tri‐coordinated Sn(II) center. The present study supplements the experimental characterization of SnX_n·mpy and, in general, it sheds light on the coordination of heteroaromatic nitrogen to tin. The survey of the Cambridge Structural Database revealed that such coordination occurred in a number of crystal structures.     

Resonance Raman spectroscopy as a probe of the crystallite size of MoS2 nanoparticles

Irregularly shaped and inorganic fullerene-like MoS₂ compounds were characterized by Resonance Raman spectroscopy using an exciting line at 633 nm. It was shown that the relative intensity of the longitudinal acoustic mode at 226 cm⁻¹ and its overtone strongly depends on the MoS₂ crystallite size but not on the size of the particles made of agglomerated crystallites. This technique appeared as a promising probe to characterize in situ very small crystallites that are not observed by XRD.     

Structure and electronic properties of MNO3 (M: Li,Na, K,NH4) under pressure: DFT-D study

The structural and electronic properties of crystalline nitrates have been investigated within the framework of density functional theory including van der Waals interactions. Pressure behavior of nitrates has been investigated using semiempirical dispersion correction scheme DFT-D. The optimizations of the crystal structures have been done with full relaxation of the atomic positions and lattice parameters under the experimentally determined crystal symmetries. The pressure dependences of geometrical parameters, band gaps, densities of states, charge distributions, overlap populations and atomic charges are computed. The predicted results agree well with the available experimental data.     

Modification of bidentate bis(N-heterocyclic imine) ligands for low-valent main group complexes

The synthesis of modified neutral bis-NHI (NHI is N-heterocyclic imine) ligands and their application for the stabilization of tetryliumylidenes are reported. The ligands’ scaffolding consists of either saturated or methylated imidazoline backbones, and the bridge alternated from flexible ethylene to more rigid o-phenylene. Transmetalation reactivity of the cationic Sn^II compounds was tested towards LiAlH₄ and IDipp→SiCl₂ [IDipp is 1,3-bis(2,6-diisopropyl- phenyl)imidazol-2-ylidene] affording the respective aluminium and silicon complexes.     

Mechanical and electrical response variation of the polyurethane–tin oxide–carbon nanotube composite microfiber depending on the chemical solution

Toward the goal of smart sensor systems for wearable electronics, polymer microfiber‐based free‐standing sensors benefit from excellent flexibility, decent ductility, and easy wearability in comparison with thin‐film‐based sensing devices. Herein, we report a hydrophobic and conducting single‐strand microfiber‐based liquid‐phase chemical sensor consisting of polyurethane (PU), tin oxide (SnO₂), and carbon nanotube (CNT) composites with applying a (1H,1H,2H,2H‐heptadecafluorodec‐1‐yl) phosphonic acid (HDF‐PA)‐based self‐assembled monolayer. The free‐standing HDF‐PA‐treated PU–SnO₂–CNT composite microfiber showing selective filtering properties with the repellency of water and the penetration of an organic solvent is electrically and mechanically characterized. Finally, the single‐strand HDF‐PA‐treated PU–SnO₂–CNT composite microfiber‐based chemical sensor, which shows excellent mechanical properties and aqueous stability, is demonstrated to detect the presence of a chemical in pure water or counterfeit gasoline in pure gasoline by observing mechanical changes, especially variations in the length and diameter of the fiber, and monitoring the electrical resistance change. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 495–502     

Tin powder‐promoted diastereoselective allylation of chiral acylhydrazones

An efficient method for the allylation of chiral acylhydrazones derived from aldehydes has been developed to give the corresponding allylic hydrazides in good yields and diastereoselectivities. The method uses a combination of tin powder and allylic bromide as allylation system, which avoids the use of toxic allylic stannanes while retaining their merits.     

Syntheses and molecular structures of four inorganic–organic hybrid compounds from N-containing aromatic bases and perchlorometallates of Zn,Cu, Sn,and Fe

Four organic–inorganic crystals, [(HL1)₂(ZnCl₄)]·H₂O (1) (L1?=?2-methylquinoline), [(HL1)₂(CuCl₄)] (2), [(HL2)₂SnCl₆] (3) (L2?=?6-bromobenzo[d]thiazol-2-amine), and [(HL3)FeCl₄] (4) (L3?=?5,7-dimethyl-1,8-naphthyridine-2-amine), derived from N-containing aromatic Brønsted bases and metal(II) chlorides (zinc(II) chloride, copper(II) chloride dihydrate, tin(II) chloride dihydrate, and iron(III) chloride hexahydrate) were prepared at room temperature and characterized by IR, X-ray structure analysis, elemental analysis, and TG analysis. The crystals are built up by perchlorometallates (Zn, Cu, Sn, and Fe) associated with organic cations through multiple non-covalent associations. X-ray diffraction analysis reveals that 1 and 2 have 3-D network structures built from hydrogen bonds between the cations and chlorometallates. Water molecules play an important role in structure extension in 1. Anhydrous 3 and 4 produced from 2-aminoheterocyclic derivatives display 2-D sheet structures. Arrangements of anions and cations are dominated by shape and size of cations, and also by the different structures of the chlorometallates as well as non-bonding interactions in the crystal structures. Except for 1, the other compounds are thermally stable below 240°C.     

Different Species of Mercury in the Livers of Tropical Dolphins

Abstract

Four kinds of mercury species (inorganic mercury (Hg_inorg), methylmercury (MeHg), total organic mercury (ΣHg_org), and insoluble mercury, deemed to be mercuric selenide (HgSe), were determined in the livers of dolphins from the Brazilian coast. The MeHg was identified and quantified in the toluene layer on a Gas Chromatograph with an Electron Capture Detector (GC-ECD). The ΣHg_org was isolated by acid leaching (H₂SO₄-KBr-CuSO₄) and then extracted into CH₂Cl₂. The ΣHg_org and Hg_inorg were determined by Cold-Vapor Atomic Absorption Spectroscopy (CV-AAS). The MeHg was the smallest fraction of Hg_tot, with a median of 9%, whereas the highest fraction of the Hg_tot was as HgSe, corresponding to 53%. The fractions of Hg_inorg and ΣHg_org corresponded to 30% and 39%, respectively. The lowest fraction of MeHg and the highest fraction of HgSe in the liver of all animals are related to different capacities or strategies of detoxification of methylmercury in this organ.     

Pt(II) Complexes with Azolate‐containing Bidentate Chelate: Design,Photophysics, and Application

This review is aimed at the current research progression of a unique class of Pt(II ) metal complexes bearing at least one azolate‐containing bidentate chelate. The azole fragment can link to a neutral heteroaromatic entity or another azole and form bidentate chelates, such as monoanionic 3‐pyridyl‐1H ‐pyrazole and derivatives, dianionic 3,3′‐bi‐1H ‐pyrazole, 3,3′‐(1‐methylethylidene)‐bis‐1H ‐pyrazole, and their analogs. These azole‐containing chelates readily react with a variety of Pt(II) reagents to afford the corresponding bis‐bidentate Pt(II) complexes. Most of them were highly emissive in solution, doped polymer matrix, thin film, and even as crystal or powder, due to the high ligand field strength exerted by these chelates and their high propensity in forming the singular square‐planar architecture and intermolecular aggregates with substantially strengthened Pt⋯Pt interaction, according to their structural design. Therefore, they hold bright prospects in academic research and future optoelectronic applications such as organic light‐emitting diodes.