https://doi.org/10.1039/D4NJ05047A
Abstract: 1-Ethyl-3-methylimidazolium dinitramide (EMImDN), an energetic ionic liquid, was synthesized and characterized by IR, 1H NMR, 13C NMR, 15N NMR, and 17O NMR techniques. The thermal properties of EMImDN were investigated through DSC and TG analyses. The TG curve revealed three consecutive exothermic decomposition events with peak temperatures at 223 oC, 277 oC and 308 oC, accompanied by an 80 % mass loss between 180 oC and 280 oC. The thermal decomposition kinetics were analyzed using the Kissinger method and Flynn-Wall-Ozawa isoconversional method. The activation energies for the three decomposition stages were calculated to be 41.1, 35.9 and 43.2 kcal/mol respectively by Kissinger method and 39.0, 36.8 and 42.6 kcal/mol respectively by FWO method. Pyrolysis GC-MS analysis identified the decomposition products, and the decomposition mechanism was predicted to involve dealkylation of the imidazole ring via bimolecular nucleophilic substitution (SN2). The proposed decomposition mechanism was further supported by density functional theory (DFT) calculations at B3LYP/6-311+G(d,p) level. Additionally, the molar enthalpy of formation of EMImDN (+54.5 kcal/mol), determined through combustion calorimetry, underscores the energetic nature of this ionic liquid. Notably, a 10 wt.% solution of NH3BH3 in EMImDN exhibited hypergolicity with red fuming nitric acid. Preliminary investigations into the interactions of EMImDN with HNO3 and NH3BH3 provide insights into the initial stages of this hypergolic reaction.
https://doi.org/10.1039/d4dt02703e
Abstract
Activating atmospheric dinitrogen (N2), a molecule with a remarkably strong triple bond, remains a major challenge inchemistry. This theoretical study explores the potential of superbase phosphines, specifically those decorated withimidazolin-2-imine ((ImN)3P) and imidazolin-2-methylidene ((ImCH)3P) to facilitate N2 activation and subsequent hydrazine(H2NNH2) formation. Using density functional theory (DFT) at the M06L/6-311++G(d,p) level, we investigated the interactionsbetween these phosphines and N2. Mono-phosphine-N2 complexes exhibit weak, noncovalent interactions (-0.6 to -7.1kcal/mol). Notably, two superbasic phosphines also form high-energy hypervalent complexes with N2, albeit at significantlyhigher energies. The superbasic nature and potential for hypervalency of these phosphines lead to substantial N2 activationin bis-phosphine-N2 complexes, where N2 is “sandwiched” between two phosphine moieties through hypervalent P-N bonds.Among the phosphines studied, only (ImN)3P forms an exothermic sandwich complex with N2, stabilized by hydrogenbonding between the ImN- substituents and the central N2 molecule. A two-step, exothermic hydrogen transfer pathwayfrom (ImN)3P to N2 results in the formation of a bis-phosphine-diimine (HNNH) sandwich complex. Subsequent hydrogentransfers lead to the formation of a bis-phosphine-hydrazine (H2NNH2) complex, a process that, although endothermic,exhibits surmountable activation barriers. The relatively low energy requirements for this overall transformation suggest itspotential feasibility under optimized conditions. This theoretical exploration highlights the promise of superbase phosphinesas a strategy for metal-free N2 activation, opening doors for the development of more efficient and sustainable nitrogenfixation and utilization methods.
https://doi.org/10.1016/j.jiec.2024.11.025
Abstract
The development of cost-effective water-treatment methods to remove toxic industrial contaminants is of burgeoning demand today. This paper discusses the superior performance of Ce doped ZnO for the photocatalytic degradation of toxic cationic and anionic dyes. The excellent degradation ability of this easily manoeuvrable solid photocatalyst developed by the facile and low-cost electrochemical method, for the simultaneous removal of multiple dyes, avoiding the need for any post treatments is successfully demonstrated with the synthetic dyes methylene blue, methyl orange, congo red and their mixture. The pH dependence of the photocatalytic efficiency is correlated with its zeta potential. The improved photocatalytic efficiency is attributed to the Ce4+↔Ce3+ redox couple acting as trap centers enhancing the production of superoxide radicals and the reduction of carrier recombination. The scavenger and cyclic stability tests confirm respectively the dominant role of superoxide radicals in photocatalysis and the reusability of the photocatalyst. The photocatalyst is characterized in detail by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Rutherford backscattering, high-resolution transmission electron microscopy, selected area electron diffraction, surface charge analysis and diffuse reflectance Spectroscopy. The study highlights the prospect of Ce doped ZnO nanostructured film as a high-performing photocatalyst for water treatment.
https://doi.org/10.1002/pssa.202400612
Abstract
A highly efficient, solid, and easily maneuverable adsorbent and photocatalyst, Li-incorporated titanate nanotubes that manifest adsorption efficiency of 98.1% and photocatalytic efficiency of 99.6% in 60 min and 97.8% and 98.5%, respectively, in a shorter duration of 20 min, is synthesized by a facile two-stage electrochemical technique. The modified nanotubes exhibit good cyclic stability of 93.7% photodegradation of malachite green dye after three continuous cycles. The adsorption data show the highest correlation for second-order pseudo kinetics and Freundlich isotherm, suggesting multilayer chemisorption with an adsorption capacity of kF ≈ 219.51 mg1–1/nL1/ng−1. Fourier transform infrared spectroscopy (FTIR) analysis of the adsorbent before and after the adsorption corroborates the findings. X-Ray photoelectron spectroscopy reveals the formation of a larger number of oxygen vacancies (Ti3+/Ti2+) that facilitate more carrier release for the production of reactive oxygen species during photocatalysis. X-Ray diffraction and transmission electron microscopy analysis confirm a secondary rutile phase formation on Li doping that promotes heterogeneous multilayer adsorption. Field-emission spectroscopic studies reveal a change in the morphology of the doped tubes with porous aggregate formation on the surface. The structural, morphological, and compositional change brought about by Li incorporation facilitates the use of titania nanotubes as an efficient adsorbent cum photocatalyst in the removal of malachite green dye.
Abstract
The study investigates the phenomenon of bond stretch isomerism (BSI) in complexes formed between alkali metals (Li, Na, K) and various non-aromatic, aromatic hydrocarbons, as well as heteroaromatic systems. The research employs density functional theory (DFT) calculations to optimize complex geometries and analyze their electronic structures using molecular electrostatic potential (MESP), charge, and spin density analyses. The results reveal that these complexes can exist in two distinct configurations: ‘loose’ long-bond isomers (lbi) that retain the original hydrocarbon geometry and ‘tight’ short-bond isomers (sbi) that undergo geometrical distortion upon complexation, with sbi generally being more stable. The interconversion between lbi and sbi occurs through a transition state. The study highlights the crucial role of electron transfer in BSI, with sbi involving valence electron transfer from the metal to the hydrocarbon, leading to zwitterionic radical complexes. In contrast, lbi exhibit a slight electron density transfer from the hydrocarbon to the metal. The presence of low-energy transition states between lbi and sbi suggests a dynamic shuttling mechanism for alkali metals, particularly Li, on hydrocarbon surfaces. The study identifies Li complexes as potential candidates for anode materials in batteries due to their stability and electron transfer properties, offering valuable insights into the design of advanced materials for energy storage applications.
https://doi.org/10.1021/acsaom.4c00330.
Abstract
Two large-flexible porphyrinoids [40]pentathiadecaphyrin(1.0.1.0.1.0.1.0.1.0) S5N5 and [48]dodecaphyrin (1.0.1.0.1.0.1.0.1.0.1.0) S6N6 were obtained through Lewis acid catalyzed condensation of thiophene containing diheterole. The single crystal X-ray structure of S6N6 revealed a twisted “figure eight” conformation whereas the optimized structure of S5N5 displayed a coplanar arrangement of thiophene and pyrrole rings. Various spectral and theoretical studies along with the photophysical investigation of the SnNn (n = 3–6) series suggested that the higher order systems (S5N5 and S6N6) were deemed to be nonaromatic due to their nonplanar conformations. The transient absorption studies revealed a strong dependence on the electronic structure with conformational flexibility due to the expansion of the macrocyclic core. The internal conversion processes become significantly fast in higher order macrocycles SnNn (n = 5–6). These macrocycles are also shown to be promising candidates for nonlinear optical materials.
https://doi.org/10.1021/acs.joc.4c01635
Abstract
Members of a new class of bifunctional amino quaternary phosphonium salts have been synthesized and utilized as catalysts in aldol condensation reactions, as demonstrated herein. These secondary amines feature a phosphonium ion connected by a carbon chain, enabling the quaternary phosphonium ion to engage in distinct cooperative noncovalent interactions. These interactions work in tandem to stabilize different transition state complexes, exclusively controlling competing amine-catalyzed aldol pathways via the Mannich mechanism. Comprehensive mechanistic investigations were conducted through theoretical calculations. This study uncovers a proximity-driven catalytic mechanism in which the distance between the N and the P+ of the bifunctional catalyst emerges as a critical factor determining catalytic efficacy. The method has been demonstrated through its application to the total synthesis of several bioactive natural products.
https://doi.org/10.1002/ejoc.202400450.
Abstract
An efficient method for the conversion of biphenyl acrylamides to dibenzoazepinones with −SCF3 incorporation is described. This operationally simple radical cascade reaction employs CAN as an oxidant and exhibits good functional group tolerance. Substrates featuring −OCH3, −CH3, −Br or −Cl at the para-position of the aromatic ring exhibits a preference for an ipso-cyclization due to the intervention of DMSO in the reaction. Density functional theory (DFT) calculations provide valuable insights into the reaction’s energetics and product selectivity.
https://doi.org/10.1088/1361-6528/ad3649.
Abstract
The removal of pollutants from water bodies is crucial for the well-being of humanity and is a topic of global research. Researchers have turned their attention to green synthesized nanoparticles for wastewater treatment due to their eco-friendly nature, biocompatibility, and cost-effectiveness. This work demonstrates the efficient removal of organic dye and both gram-positive and gram-negative bacteria from water bodies using copper-doped cerium oxide nanoparticles synthesized with MurrayaKoenigii extract. Characterized via various methods, the 15% copper doped cerium oxide nanoparticles (Cu 15% NPs) exhibited maximum Congo red dye adsorption (98% degradation in 35 min). Kinetic analysis favoured a pseudo-second-order model, indicating the chemical nature of adsorption. Equilibrium adsorption isotherms aligned with the Langmuir model, indicating homogenous monolayer dye adsorption on the doped adsorbent. The maximum uptake of adsorbate, Qm obtained from Langmuir model for Cu 15% NPs was 193 mg g−1. The study also showed enhanced antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa for Cu-doped ceria, attributed to generation of reactive oxygen species (ROS) induced by the redox cycling between Ce3+ and Ce4+. This substantiated that the green synthesized copper doped cerium oxide nanoparticles are potential candidates for adsorptive removal of Congo red dye and as antibacterial agents.
Abstract
The study investigates the phenomenon of bond stretch isomerism (BSI) in complexes formed between alkali metals (Li, Na, K) and various non-aromatic, aromatic hydrocarbons, as well as heteroaromatic systems. The research employs density functional theory (DFT) calculations to optimize complex geometries and analyze their electronic structures using molecular electrostatic potential (MESP), charge, and spin density analyses. The results reveal that these complexes can exist in two distinct configurations: ‘loose’ long-bond isomers (lbi) that retain the original hydrocarbon geometry and ‘tight’ short-bond isomers (sbi) that undergo geometrical distortion upon complexation, with sbi generally being more stable. The interconversion between lbi and sbi occurs through a transition state. The study highlights the crucial role of electron transfer in BSI, with sbi involving valence electron transfer from the metal to the hydrocarbon, leading to zwitterionic radical complexes. In contrast, lbi exhibit a slight electron density transfer from the hydrocarbon to the metal. The presence of low-energy transition states between lbi and sbi suggests a dynamic shuttling mechanism for alkali metals, particularly Li, on hydrocarbon surfaces. The study identifies Li complexes as potential candidates for anode materials in batteries due to their stability and electron transfer properties, offering valuable insights into the design of advanced materials for energy storage applications.
