Raman spectroscopic identification of the S4N- and S3- ions in blue solutions of sulfur in liquid ammonia

1-Ethyl-3-methylimidazolium Acetate as a Reactive Solvent for Elemental Sulfur and Poly(sulfur nitride)

We investigate the reactive dissolution process of poly(sulfur nitride) (SN)x in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [EMIm][OAc] in comparison to the process of elemental sulfur in the same IL. It has been known from the literature that during the reaction of S8 with [EMIm][OAc], the respective thione is formed via a radical mechanism. Here, we present new results on the kinetics of the formation of the respective imidazole thione (EMImS) via the hexasulfur dianion [S6]2- and the trisulfur radical anion [S3]•-. We can show that [S6]2- is formed first, which dissociates then to [S3]•-. Also, long-term stable radicals occur, which are necessary side products provided in a reaction scheme. During the reaction of [EMIm][OAc] with (SN)x chains, two further products can be identified, one of which is the corresponding imine. The reactions are followed by time-resolved NMR spectroscopic methods that showed the corresponding product distributions and allowed the assignment of the individual signals. In addition, continuous-wave (CW) EPR and UV/vis spectroscopic measurements show the course of the reactions. Another significant difference in both reactions is the formation of a long-term stable radical in the sulfur-IL system, which remains active over 35 days, while for the (SN)x-IL system, we can determine a radical species only with the spin trap 5,5-dimethyl-1-pyrrolin-N-oxide, which indicates the existence of short-living radicals. Since the molecular dynamics are restricted based on the EPR spectra, these radicals must be large.

Balancing Electrolyte Donicity and Cathode Adsorption Capacity for High-Performance LiS Batteries

LiS batteries with high theoretical capacity are attracting attention as next-generation energy storage systems. Much effort has been devoted to the introduction of cathode materials with strong adsorption to sulfide species, but it is presented that this selection should be refined in the application of high donicity electrolytes. The oxides with different adsorption capacities are explored while controlling the electrolyte donicity, confirming the trade-off effect between the donicity and the adsorption capacity for sulfur conversion. Specifically, a cathode substrate containing oxide nanoparticles of MgO, NiO, Fe₂ O₃ , Co₃ O₄ , and V₂ O₅ is prepared with spectra in adsorption capacity as well as low and high donicity electrolytes by controlling the concentration of LiNO₃ salt. Strong adsorbent oxides such as Co₃ O₄ and V₂ O₅ cause competitive adsorption of electrolyte salts in high donicity electrolytes, resulting in poor cell performance. High cell performance is achieved on weakly adsorbing oxides of MgO or NiO with high donicity electrolytes; the MgO-containing cathode cell delivers a high discharge capacity of 1394 mAh g^-1 at 0.2 C. It is believed that understanding the interactions between electrolytes and adsorbent substrates will be the cornerstone of high-performance LiS batteries.

Anticancer activity of indapamide adsorbed on gold nanoparticles: DFT, in-silico, and in-vitro analysis

The adsorption properties of the lung cancer agent indapamide (IND) on gold nanoparticles (AuNPs), were studied with the help of surface-enhanced Raman scattering techniques. The structure-activity of the IND and INDA molecule has been studied using DFT/B3LYP methodology. NBO analysis reveals that, both the molecules are stabilized by a C─H^… O intramolecular hydrogen bonding, apart from the conjugative and intramolecular charge transfer interactions. The analysis of the electron density of frontier molecular orbital analysis gives a comparative idea of the reactivity, the low kinetic stability, and low value of energy gap indicating the electron transport in the molecule and thereby its bioactivity. The molecular electrostatic potential, local and global reactivity indicators predict the reactive site of the molecules. FT-IR, FT-Raman, and surface-enhanced Raman scattering have been investigated and compared with the theoretical prediction. Effective in-silico (molecular docking) biological activity screening of the molecules was checked on lung cancer cells. In-vitro (surface-enhanced Raman scattering techniques and MTT assay) analysis confirms the results from the in-silico analysis. This study promotes the potential of SERS agents for targeted drug delivery and photothermal therapy and the novelty of the IND and INDA molecule against lung cancer activity.

A Robust and Biocompatible Bismuth Ellagate MOF Synthesized Under Green Ambient Conditions

The first bioinspired microporous metal-organic framework (MOF) synthesized using ellagic acid, a common natural antioxidant and polyphenol building unit, is presented. Bi2O(H2O)2(C14H2O8)·nH2O (SU-101) was inspired by bismuth phenolate metallodrugs, and could be synthesized entirely from nonhazardous or edible reagents under ambient aqueous conditions, enabling simple scale-up. Reagent-grade and affordable dietary supplement-grade ellagic acid was sourced from tree bark and pomegranate hulls, respectively. Biocompatibility and colloidal stability were confirmed by in vitro assays. The material exhibits remarkable chemical stability for a bioinspired MOF (pH = 2-14, hydrothermal conditions, heated organic solvents, biological media, SO2 and H2S), attributed to the strongly chelating phenolates. A total H2S uptake of 15.95 mmol g-1 was recorded, representing one of the highest H2S capacities for a MOF, where polysulfides are formed inside the pores of the material. Phenolic phytochemicals remain largely unexplored as linkers for MOF synthesis, opening new avenues to design stable, eco-friendly, scalable, and low-cost MOFs for diverse applications, including drug delivery.

Critical Role of Anion Donicity in Li2S Deposition and Sulfur Utilization in Li-S Batteries

Lithium-sulfur batteries offer a high theoretical gravimetric energy density and low cost, but the full utilization of the sulfur electrode has been limited by the premature passivation of insulating lithium sulfide (Li₂S). Anion has been one of the major parameters to improve Li-S batteries in addition to solvent, additives, and electrode structures. Here, we reveal the role of anion donicity on the passivation of Li-S battery and its underlying working mechanism. We show that anions with high donicity effectively reduce the charge-transfer resistance during the cycling of Li-S cells and alleviate the Li₂S passivation by transforming the dense film Li₂S to porous three-dimensional flake Li₂S. UV-vis spectroscopy revealed that anions with higher donicity exhibit higher Li₂S₄ solubility, which is consistent with their stronger bonding to Li⁺, as revealed by nuclear magnetic resonance and density functional theory calculations. Our study reveals the role of anion donicity in Li₂S passivation and its underlying mechanism, offering rational design consideration for electrolyte salts in achieving high sulfur utilization and high energy efficiency for Li-S batteries.

The role of polysulfide dianions and radical anions in the chemical, physical and biological sciences, including sulfur-based batteries

Polysulfide dianions and radical anions play a crucial role in biological chemistry, geochemical processes, alkali metal–sulfur batteries, organic syntheses, coordination chemistry, and materials sciences.

Photoinduced Sulfur-Nitrogen Bond Rotation and Thermal Nitrogen Inversion in Heterocumulene OSNSO

An exotic ternary S, N, O heterocumulene OSNSO in syn-syn (A) and syn-anti (B) conformations has been generated in the gas phase through flash vacuum pyrolysis of CF₃S(O)NSO at 700 K. Upon visible light irradiation (570 ± 20 or 532 nm), both A and B, isolated in cryogenic matrices (N₂, Ne, Ar, and Kr, <30 K), convert to a higher-energy anti-anti conformer (C). The reverse conformational transformation occurs either through S═N bond rotation (C to A and B) under visible light irradiation (400 ± 20 nm) at 2.8 K or through thermal nitrogen inversion (C to A) in the temperature range of 20-30 K, for which an exceptionally low activation barrier of 1.18 ± 0.07 kcal mol^-1 has been experimentally determined.

Fundamental chemistry of binary S,N and ternary S,N,O anions: analogues of sulfur oxides and N,O anions

The fundamental chemistry and significance of S,N and S,N,O anions and their conjugate acids in a variety of settings are discussed.

Sulfuration of the C(sp2)–H bond of enaminones: a protocol for the synthesis of thioether using elemental sulfur as a sulfurating reagent

Sulfuration reaction of the C(sp²)–H bond of enaminones with elemental sulfur in the presence of CuBr/K₃PO₄ was carried out. It provided an efficient method for the synthesis of thioethers and selenides in moderate to good yields.

In situ Raman spectroscopy of sulfur speciation in lithium-sulfur batteries

In situ Raman spectroscopy and cyclic voltammetry were used to investigate the mechanism of sulfur reduction in lithium-sulfur battery slurry cathodes with 1 M lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME)/1,3-dioxolane (DIOX) (1/1, v/v). Raman spectroscopy shows that long-chain polysulfides (S8(2-)) were formed via S8 ring opening in the first reduction process at ∼2.4 V vs Li/Li(+) and short-chain polysulfides such as S4(2-), S4(-), S3(•-), and S2O4(2-) were observed with continued discharge at ∼2.3 V vs Li/Li(+) in the second reduction process. Elemental sulfur can be reformed in the end of the charge process. Rate constants obtained for the appearance and disappearance polysulfide species shows that short-chain polysulfides are directly formed from S8 decomposition. The rate constants for S8 reappearance and polysulfide disappearance on charge were likewise similar. The formation of polysulfide mixtures at partial discharge was found to be quite stable. The CS2 additive was found to inhibit the sulfur reduction mechanism allowing the formation of long-chain polysulfides during discharge only and stabilizing the S8(2-) product.