Journal of Chemical Sciences最新文献

The compound, Bi₂ZnB₂O₇, stabilized in the melilite structure, has been prepared and characterized. The partial substitution of transition elements (Co²⁺, Ni²⁺ and Cu²⁺ ions) in place of tetrahedral Zn²⁺ ions gave rise to colored compounds. The origin of the color in the compounds was understood based on the allowed d-d transitions. The near-IR reflectivity studies indicate reasonable NIR reflectivity with values in the range of 50–65%. The tetrahedral B³⁺ ions were partially replaced by Al³⁺ ions, giving rise to a new melilite analogue, Bi₂Zn(B_1.5Al_0.5)O₇. The Bi³⁺ ions, substituted by rare-earth ions (Eu³⁺, Tb³⁺ and Tm³⁺), resulted in compounds exhibiting intense red, green and blue emissions. The life-time studies indicated an average life time in the milliseconds region for all three substituted compounds. The substitution of the same ions in place of Y³⁺ ions in (Bi_1.9Y_0.1)ZnB₂O₇ compounds also resulted in a similar behaviour. The compounds, Bi₂ZnB₂O₇, Bi₂Zn(B_1.5Al_0.5)O₇, (Bi_1.75Y_0.25)ZnB₂O₇ and (Bi_1.75La_0.25)ZnB₂O₇, were examined for their dielectric behaviour at room temperature, which gave reasonably good values with minimal dielectric loss. The present studies clearly indicates that the melilite structure could be adaptable, though in a limited way, resulting in new colored compounds and excellent luminescence behaviour.

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The compound, Bi₂ZnB₂O₇, was explored towards new colored compounds by substituting divalent transition metal ions Co²⁺/Ni²⁺/Cu²⁺ in place of Zn²⁺ ion in the compound. Substitution of rare-earth ions at the bismuth site gives rise to intense characteristic emission.

A bis-pyridinium calix[4]pyrrole derivative has been synthesized and investigated for its supramolecular interactions with nerve agent surrogates. The receptor promotes the degradation of organophosphorus nerve agent surrogates by facilitating the release of fluoride and cyanide leaving groups. The released anions are subsequently detected via fluorescence response, enabling dual functionality in degradation and sensing. The binding interactions and mechanistic insights were elucidated through NMR spectroscopy, fluorescence titration, and computational studies, confirming the receptor’s role in modulating leaving group dissociation. These findings contribute to the development of supramolecular strategies for chemical defence and environmental detoxification.

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A bis-pyridinium calix[4]pyrrole derivative promotes the degradation of organophosphorus nerve agent surrogates by facilitating the release of fluoride and cyanide leaving groups. The released anions are subsequently detected via fluorescence response, enabling dual functionality in degradation and sensing. This supramolecular approach provides insights into molecular recognition and chemical detoxification strategies.

Supercapacitors are among the most promising electrochemical energy-storage devices, bridging the gap between traditional capacitors and batteries in terms of power and energy density. Their charge-storage performance is largely influenced by the properties of electrode materials, electrolytes and the underlying charge-storage mechanisms. This review provides an overview of the fundamental principles of electrochemical energy storage in supercapacitors, highlighting various energy-storage materials and strategies for enhancing their performance, with a focus on manganese- and nickel-based materials. Key factors, such as electrode surface area, porosity and electrical conductivity are identified as critical contributors to performance. Approaches, such as nanostructuring, chemical activation and integration with conductive graphitic carbon or conducting polymers are extensively utilized to optimize these properties. The charge-storage performance of nanostructured Mn- and Ni-based materials investigated in our laboratory and the charge storage in nanoporous electrode are presented. Finally, the challenges and prospects of these materials for practical applications, including wearable and flexible supercapacitors, are discussed.

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Electrochemical energy storage with supercapacitors using rationally designed electrode materials is reviewed.

Krossing et al. reported a new method for the synthesis and characterization of a cationic [Mn(CO)₅(n-pentane)]⁺ complex in both solution and solid state. The elegant strategy significantly improved the lifetime of the σ-pentane complex in solution at room temperature and allowed crystallization at 0 °C.

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This news story article summarizes the development of various strategies for the characterization (NMR, X-ray) of sigma-alkane complexes. Most notably, a recently discovered route by Krossing and coworkers to make a n-pentane C-H bond ligated onto a highly electron-deficient cationic manganese(I) carbonyl centre is highlighted.

We have reported an effective, seed-assisted organic structure directing agent (OSDA) free synthesis of ferrierite (FER) zeolites. In the current study, we have observed effects of physicochemical properties of two different seeds over synthesis of FER zeolites. The physicochemical properties of seeds, such as particle size and phase purity impart significantly over crystallization time and overall synthesis duration, costs of process and crystalline nature of FER zeolites. It is noteworthy that particle size of seed mainly affects the kinetics of crystallization for concerned FER zeolites. The synthesized zeolites were well characterized by XRD, FESEM, TEM, Raman spectroscopy, ²⁷Al and ²⁹Si MAS NMR, EDAX and BET surface area analyser to get more insights. We also evaluated, the catalytic activity of synthesized FER zeolites in oleic acid isomerization study to derive branched-chain fatty acids formation and attempted their structure and catalytic activity relationship with respect to purity of phases in seed.

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Two novel phenyl or biphenyl-based organogelators G1 and G2 were designed and synthesized. Owing to the non-coplanar geometry of the two benzene rings in biphenyl group, gelling performance of G1 was dramatically better than that of G2. Hydrogen bonding, π–π stacking and van der Waals interactions were emerged as the dominant intermolecular forces governing the self-assembly-driven gelation of G1. G1-DMSO gel could act as a multi-stimuli-responsive sensor for detecting Cu²⁺ and present selective gel–sol transformation and colorimetric changes. Furthermore, the selective ion-recognition properties of G1-DMSO gel for Cu²⁺ were investigated by UV–Vis spectra and ESI-MS. It was found that the detection limit for Cu²⁺ was 9.1445 × 10⁻⁶ M and the binding stoichiometric ratio of G1 to Cu²⁺ was 1:1.

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A microwave-assisted and solvent-free protocol for secondary and benzyl alcohols oxidation to the corresponding ketones and aldehydes, using the inexpensive and widely available Cu(NO₃)₂·2.5H₂O salt as catalyst and aqueous tert-butyl hydroperoxide (TBHP) as oxidant, has been developed. The present strategy allows the isolation of the oxidation products with yields up to 80% for the majority of the tested substrates. Extremely short reaction times and the usage of low-power microwave irradiation are factors that contribute to the smoothness of the process and are shown as an asset of the described experiment. Remarkably, the approach features a one-pot procedure, an earth-abundant copper catalyst, a wide substrate scope (22 alcohols) and a high compatibility with several functional groups.

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As an ecological, widely available and economical material, the copper salt Cu(NO3)2∙2.5H2O show a high performance as catalyst in the oxidation of a series of secondary and benzyl alcohols. The developed protocol, using TBHP as oxidant and assisted by microwave radiation, proceeds without the use of an organic solvent and is very chemoselective tolerating the presence of several functional groups.

This study uses computational methods to explore the triple hydrogen bonding between cytosine and guanine. It specifically focuses on two tautomers: the GC tautomer, which forms during DNA replication, and the tautomer resulting from double proton transfer, denoted as G*C*. The latter tautomer is linked to genetic mutations. The geometric, vibrational, and electronic structures of both tautomers have been calculated using DFT-B3LYP and MP2 levels of theory. The results are then compared to those of the non-interacting bases. The findings indicate that hydrogen bonding is moderately strong for both tautomers, with electrostatic interaction being the primary component. While the variations in the HOMO energy contribute to the stabilization of the triple hydrogen bond in G*C*, the kinetics of the reaction from GC to G*C* is hindered by a relatively high potential barrier. This barrier is mainly caused by a significant increase in nuclear repulsion within G*C*, which is not adequately counterbalanced by the favourable changes in HOMO energies.

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General methods for the highly site-selective monocoupling of alkyl 2,4- and 2,5-dihalobenzoates have been discovered. By switching from PdCl₂(PCy₃)₂/P(p-MeOPh)₃ to Pd(OAc)₂/L9, the preferred coupling site can be shifted from the C2-position to the C4 or C5-position. The formation of the substituted alkyl monohalobenzoate derivatives is highly site-selective and tolerant to both electron-withdrawing and electron-donating groups on aryl and heteroaryl titanium reagents and the reaction gives twenty-four substituted alkyl monohalobenzoate derivatives (except for 4ea, the other were novel compounds) were prepared and their structure was confirmed by FTIR, spectroscopy, ¹H and ¹³C NMR, and mass spectrometry. This simple synthetic route is designed to improve the rapid construction of mutiple aryl cross-coupling products.

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The same substrate alkyl 2,4- and 2,5-dihalobenzoates can selectively generate C2-position and C4- or C5-position products by switching catalytic system from PdCl₂(PCy₃)₂/P(p-MeOPh)₃ to Pd(OAc)₂/L9. The reaction gives twentyfour substituted alkyl monohalobenzoate derivatives, and the simple synthetic route is designed to improve the rapid construction of mutiplearyl cross-coupling products.

Optimizing metal nanoparticles (NPs) efficiency through uniform dispersion and downsizing to smaller clusters/atoms holds substantial potential to enhance catalytic activity, thereby improving the sensitivity and selectivity of the sensor. Herein, we report an ultra-high dispersion of Pd (downsized to <1 nm), achieved by synthesizing Pd/NC-ZnO via a reverse sintering route derived from Pd@ZIF-8. As a proof-of concept, uniform dispersion of Pd in Pd/NC-ZnO demonstrated a chemiresistive hydrogen (H₂) sensor with response of 4.6 ± 0.2% and response/recovery times of 6.1 ± 0.3/5.8 ± 0.3 s, respectively towards 1% H₂ at 120 °C, while Pd@ZIF-8, the precursor material remained innocent for sensing H₂. The sensor exhibited selective detection towards H₂ among typically interfering gases and was active for sensing at room temperature despite low loading of Pd (0.09 wt.%). This work highlights judicious usage of Pd by means of high dispersion and small-sized clusters/atoms stabilized by ideal supports to achieve low-cost, rapid H₂ sensors.

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Despite low Pd loading (0.09 wt.%), ultra-high dispersion of Pd through reverse sintering from Pd@ZIF-8 enabled low-cost and rapid H₂ detection. The sensor Pd/NC-ZnO showed selective detection towards H₂ among typically interfering gases and was active for sensing at room temperature.