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.
