Facile synthesis of vicinal halohydrins via organocatalytic halogen nucleophile-induced regioselective opening of epoxides

Background: The calix[4]pyrrole is reported as a novel organocatalyst for regioselective ring opening of epoxides under mild reaction conditions. Methods: The reaction involves elemental halogen as a nucleophile to afford vicinal halohydrins in good to excellent yield (75-95%). Results : The reactivity of the halide anion in the reaction is governed by different factors, including solvent polarity, temperature and non-covalent interactions of the functional group present on calix[4]pyrrole moiety with halide ions. Conclusion: An efficient methodology has been developed for the regioselective synthesis of halohydrins in good to excellent yields.

SYNTHESIS AND PHYSICOCHEMICAL PROPERTIES OF PROTON IONIC LIQUIDS WITH TETRACHLOROPALLADATE ANION

Синтезированы протонные металлсодержащие ионные жидкости с катионом аммония различной структуры и тетрахлорпалладат анионом. Изучены их физико-химические и спектральные характеристики. Установлено, что замена галогенид-аниона в протонированной соли аммония на комплексный PdCl- анион приводит к повышению температуры плавления комплексов, и наблюдается гипсохромный сдвиг полос поглощения катиона в ИК- и УФ- областях спектра. Proton metal-containing ionic liquids with an ammonium cation of various structures and a tetrachloropalladate anion were synthesized. Their physicochemical and spectral characteristics are studied. It is established that the replacement of the halide anion in the protonated ammonium salt with the complex PdCl- anion leads to an increase in the melting temperature of the complexes, and a hypsochromic shift of the absorption bands of the cation in the IR and UV regions of the spectrum is observed.

Engineering of Halide Cation in All-Inorganic Perovskite with Full-Color Luminescence

All-inorganic halide perovskites are emerging as a class of superstar semiconductors with excellent optoelectronic properties and show great potential for a broad range of applications in solar cells, lighting diodes, X-ray imaging, and photodetectors. Tremendous research about their device performance has been performed since 2015. In this study, we synthesized the all-inorganic perovskite by the hot-injection method and particularly investigated their crystal structural and photoluminescence properties. By halide anion engineering, the all-inorganic perovskites showed a high-symmetry cubic phase. They also showed a tunable optical bandgap, and almost the full color luminescence was achieved (434 to 624 nm). These basic optoelectronic properties could give a guide for further development of this area.

Colorimetric Chemosensor Array for Determination of Halides

The halide anions are essential for supporting life. Therefore, halide anion analyses are of paramount importance. For this reason, we have performed both qualitative and quantitative ana- lyses of halides (chloride, bromide, iodide) using the Tl(III) complex of azodye, 4-(2-pyridylazo)re- sorcinol (PAR), a potential new chemical reagent/sensor that utilizes the substitution reaction whereas the Tl(III)PAR complex reacts with a halide to yield a more stable thallium(III)-halide while releasing the PAR ligand in a process accompanied by color change of the solution. The experimental conditions (e.g., pH, ratio metal ion-to-ligand ratio, etc.) for the substitution reaction between the metal complex and a halide were optimized to achieve increased sensitivity and a lower limit of detection (chloride 7 mM, bromide 0.15 mM, iodide 0.05 mM). It is demonstrated that this single chemosensor can, due to release of colored PAR ligand and the associated analyte-specific changes in the UV/VIS spectra, be employed for a multicomponent analysis of mixtures of anions (chloride + bromide, chloride + iodide, bromide + iodide). The spectrophotometric data evaluated by artificial neural networks (ANNs) enable distinguishing among the halides and to determine halide species concentrations in a mixture. The Tl(III)-PAR complex was also used to construct sensor arrays utilizing a standard 96-well plate format where the output was recorded at several wavelengths (up to 7) using a conventional plate reader. It is shown that the data obtained using a digital scanner employing only three different input channels may also be successfully used for a subsequent ANN analysis. The results of all approaches utilized for data evaluation were similar. To increase the practical utility of the chemosensor, we have developed a test paper strip indicator useful for routine naked-eye visual determination of halides. This test can also be used for halide anion determination in solutions using densitometer. The methodology described in this paper can be used for a simple, inexpensive, and fast routine analysis both in a laboratory as well as in a field setting.

Reconfiguring the band-edge states of photovoltaic perovskites by conjugated organic cations

The band edges of metal-halide perovskites with a general chemical structure of ABX3 (A, usually a monovalent organic cation; B, a divalent cation; and X, a halide anion) are constructed mainly of the orbitals from B and X sites. Hence, the structural and compositional varieties of the inorganic B–X framework are primarily responsible for regulating their electronic properties, whereas A-site cations are thought to only help stabilize the lattice and not to directly contribute to near-edge states. We report a π-conjugation–induced extension of electronic states of A-site cations that affects perovskite frontier orbitals. The π-conjugated pyrene-containing A-site cations electronically contribute to the surface band edges and influence the carrier dynamics, with a properly tailored intercalation distance between layers of the inorganic framework. The ethylammonium pyrene increased hole mobilities, improved power conversion efficiencies relative to that of a reference perovskite, and enhanced device stability.