Search Results (49)

The enrichment of ⁶Li isotopes from a natural stage of 7.6% to above 59% is required for the development of next-generation green technologies capable of sustaining climate change mitigation and energy-mix targets. In this study, we developed two categories of custom laboratory-made organic membranes, membranes that were non-impregnated before electromigration (AI-1) and membranes impregnated with LiNTf₂ (AI-2), to evaluate their performance in lithium isotope separation. Both types of membranes were exposed in synthesis to ionic liquid and crown ether. The objective of the study was to test the performance of membranes in separating lithium isotopes from a lithium-loaded organic phase in an aqueous solution with variable potentials and time intervals. The results show that the impregnated AI-2 membranes increased the enrichment of ⁶Li in the early stages, and the effect decreased after 25 h. The efficiency of lithium isotope enrichment was positively related to the potential profile applied, migration time, and concentration of organic solution in the anode chamber. The 0.5 mol/L Bis-(trifluoromethane) sulfonimide lithium salt (Li[NTf₂]) with 0.1 M tetra butyl ammonium perchlorate (TBAP) in acetonitrile (CH₃CN) ionic solution significantly improved Li isotope separation compared with an aqueous environment with higher salt concentrations. The maximum isotopic separation coefficient (α) for AI-1.2 (15-crown-5 ether and 1 mol/L LiNTf₂ in TBAP solution after 48 h of electromigration) gradually increased to 1.0317. Our results demonstrated that in the laboratory-made setup described, the migration efficiency and Li isotope separation in the catholyte environment needed a minimum of 9 V and a migration time of 6 h, respectively; these values varied with the concentration of the organic solution in the anode chamber. The ability of laboratory-engineered membranes to impart isotope selectivity and enhance permselectivity or selectivity towards singly charged ions was demonstrated through the functionality of single-collector inductively coupled plasma mass spectrometry (ICP-MS). This technology is particularly valuable and commercially feasible for future lithium isotope research in nuclear technology. Full article

The complex of hypofluorous acid with acetonitrile—HOF•CH₃CN—is the only substance possessing a truly electrophilic oxygen. This fact makes it the only tool suitable for transferring oxygen atoms to sites that are not accessible to this vital element. We will review here most of the known organic reactions with this complex, which is easily made by bubbling dilute fluorine through aqueous acetonitrile. The reactions of HOF•CH₃CN with double bonds produce epoxides in a matter of minutes at room temperature, even when the olefin is electron-depleted and cannot be epoxidized by any other means. The electrophilic oxygen can also substitute deactivated tertiary C-H bonds via electrophilic substitution, proceeding with full retention of configuration. Using this complex enables transferring oxygen atoms to a carbonyl and oxidizing alcohols and ethers to ketones. The latter could be oxidized to esters via the Baeyer–Villiger reaction, proving once again the validity of the original Baeyer mechanism. Azines are usually avoided as protecting groups for carbonyl since their removal is problematic. HOF•CH₃CN solves this problem, as it is very effective in recreating carbonyls from the respective azines. A bonus of the last reaction is the ability to replace the common ¹⁶O isotope of the carbonyl with the heavier ¹⁷O or ¹⁸O in the simplest and cheapest possible way. The reagent can transfer oxygen to most nitrogen-containing molecules. Thus, it turns practically any azide or amine into nitro compounds, including amino acids. This helps to produce novel α-alkylamino acids. It also attaches oxygen atoms to most tertiary nitrogen atoms, including certain aromatic ones, which could not be obtained before. HOF•CH₃CN was also used to make five-member cyclic poly-NO derivatives, many of them intended to be highly energetic materials. The nucleophilic sulfur atom also reacts very smoothly with the reagent in a wide range of compounds to form sulfone derivatives. While common sulfides are easily converted to sulfones by many orthodox reagents, electron-depleted ones, such as R_f-S-Ar, can be oxidized to R_f-SO₂-Ar only with this reagent. The mild reaction conditions also make it possible to synthesize a whole range of novel episulfones and offer, as a bonus, a very easy way to make S^xO₂, x being any isotope variation of oxygen. These mild conditions also helped to oxidize thiophene to thiophen-S,S-dioxide without the Diels–Alder dimerizations, which usually follow such dioxide formation. The latter reaction was a prelude to a series of preparations of [all]-S,S-dioxo-oligothiophenes, which are important for the efficient preparation of active layers in field-effect transistors (FETs), as such oligomers are considered to be important for organic semiconductors for light-emitting diodes (LEDs). Several types of these oligothiophenes were prepared, including partly or fully oxygenated ones, star-oligothiophenes, and fused ones. Several [all]-S,S-dioxo-oligo-thienylenevinylenes were also successfully prepared despite the fact that they also possess carbon–carbon p centers in their molecules. All oxygenated derivatives have been prepared for the first time and have lower HOMO-LUMO gaps compared to their parent compounds. HOF•CH₃CN was also used to oxidize the surface of the nanoparticles of oligothiophenes, leaving the core of the nanoparticle unchanged. Several highly interesting features have been detected, including their ability to photostimulate the retinal neurons, especially the inner retinal ones. HOF•CH₃CN was also used on elements other than carbon, such as selenium and phosphor. Various selenides were oxidized to the respective selenodioxide derivatives (not a trivial task), while various phosphines were converted efficiently to the corresponding phosphine oxides. Full article

Interaction of [Sn(OtBu)₄] with the acid 2,2′-diphenylgylcine, Ph₂C(X)CO₂H (X = NH₂), affords the complex {Sn[Ph₂C(NH₂)(CO₂)]₄}·2MeCN (1·2MeCN) after work-up, whereas when X = OH (benzilic acid), the complex {Sn[Ph₂C(O)(CO₂)]₂(CH₃CO₂H)₂} (2) is isolated. In 1·2MeCN, the four 2,2′-diphenylglycinate ligands adopt three different coordination modes (two N,O-chelates, an O,O-chelate, and a monodentate carboxylate ligand), whilst in 2, two cis-O,O-chelate ligands are present along with two acetic acid ligands, the latter being derived from hydrolysis of acetonitrile. Both 1 and 2 have been screened as catalysts for the ring opening polymerization of ε-caprolactone and δ-valerolactone; for comparison, the commercial catalyst [Sn(Oct)₂], where Oct = 2-ethylhexanoate, and the precursor [Sn(OtBu)₄] have been screened under similar conditions. The products were of low to high molecular weight for PCL and low to moderate molecular weight for PVL, with wide Ð values, and they comprised several types of polymer families, including OH-terminated, OH/OMe-terminated, and cyclic polymers. For both monomers, kinetic profiles indicated that [Sn(Oct)₂] outperformed 1, 2, and [Sn(OtBu)₄], though under certain conditions, 1 and 2 afforded high-molecular weight products with better control. Full article

Transition-metal-catalyzed nitrene transfer reactions are typically performed in organic solvents under inert and anhydrous conditions due to the involved air and water-sensitive nature of reactive intermediates. Overall, this study provides insights into the iron-based ([Fe^II(PBI)₃](CF₃SO₃)₂ (1), where PBI = 2-(2-pyridyl)benzimidazole), catalytic and stoichiometric aziridination of styrenes using PhINTs ([(N-tosylimino)iodo]benzene), highlighting the importance of reaction conditions including the effects of the solvent, co-ligands (para-substituted pyridines), and substrate substituents on the product yields, selectivity, and reaction kinetics. The aziridination reactions with 1/PhINTs showed higher conversion than epoxidation with 1/PhIO (iodosobenzene). However, the reaction with PhINTs was less selective and yielded more products, including styrene oxide, benzaldehyde, and 2-phenyl-1-tosylaziridine. Therefore, the main aim of this study was to investigate the potential role of water in the formation of oxygen-containing by-products during radical-type nitrene transfer catalysis. During the catalytic tests, a lower yield was obtained in a protic solvent (trifluoroethanol) than in acetonitrile. In the case of the catalytic oxidation of para-substituted styrenes containing electron-donating groups, higher yield, TON, and TOF were achieved than those with electron-withdrawing groups. Pseudo-first-order kinetics were observed for the stoichiometric oxidation, and the second-order rate constants (k₂ = 7.16 × 10⁻³ M⁻¹ s⁻¹ in MeCN, 2.58 × 10⁻³ M⁻¹ s⁻¹ in CF₃CH₂OH) of the reaction were determined. The linear free energy relationships between the relative reaction rates (logk_rel) and the total substituent effect (TE, 4R-PhCHCH₂) parameters with slopes of 1.48 (MeCN) and 1.89 (CF₃CH₂OH) suggest that the stoichiometric aziridination of styrenes can be described through the formation of a radical intermediate in the rate-determining step. Styrene oxide formation during aqueous styrene aziridination most likely results from oxygen atom transfer via in situ iron oxo/oxyl radical complexes, which are formed through the hydrolysis of [Fe^III(N•Ts)] under experimental conditions. Full article

The mononuclear and dinuclear ruthenium(III) complexes trans-Ph₄P[Ru^III(acac)₂Cl₂] (1), Ph₄P[{Ru^III(acac)Cl}₂(μ-Cl)₃] (2) and trans-Ph₄P[Ru^III(acac)₂(NCS)₂]·0.5C₆H₁₄ (3·0.5C₆H₁₄) were synthesized. Single crystals of 1, 2·H₂O and 3·CH₃CN suitable for X-ray crystal structure analyses were obtained through recrystallization from DMF for 1 and 2·H₂O and from acetonitrile for 3·CH₃CN. An octahedral Ru with bis-chelate-acac ligands and axial chlorido or κ-N-thiocyanido ligands (for 1 and 3·CH₃CN) and triply µ-chlorido-bridged dinuclear Ru₂ for 2·H₂O were confirmed through the structure analyses. The Ru–Ru distance of 2.6661(2) of 2·H₂O is indicative of the existence of the direct metal–metal interaction. The room temperature magnetic moments (μ_eff) are 2.00 and 1.93 μ_B for 1 and 3·0.5C₆H₁₄, respectively, and 0.66 μ_B for 2. The temperature-dependent (2–300 K) magnetic susceptibility showed that the strong antiferromagnetic interaction (J ≤ −800 cm⁻¹) is operative between the ruthenium(III) ions within the dinuclear core. In the ¹H NMR spectra measured in CDCl₃ at 298 K, the dinuclear complex 2 showed signals for the acac ligand protons at 2.50 and 2.39 ppm (for CH₃) and 5.93 ppm (for CH), respectively, while 1 and 3·0.5C₆H₁₄ showed signals with large paramagnetic shifts; −17.59 ppm (for CH₃) and −57.01 ppm (for CH) for 1 and −16.89 and −17.36 ppm (for CH₃) and −53.67 and −55.53 ppm (for CH) for 3·0.5C₆H₁₄. Cyclic voltammograms in CH₂Cl₂ with an electrolyte of ⁿBu₄N(ClO₄) showed the Ru^III → Ru^IV redox wave at 0.23 V (vs. Fc/Fc⁺) for 1 and the Ru^III → Ru^II waves at −1.39 V for 1 and −1.25 V for 3·0.5C₆H₁₄ and the Ru^III–Ru^III → Ru^III–Ru^IV and Ru^III–Ru^III → Ru^III–Ru^IV waves at 0.91 V and −0.79 V for 2. Full article

In an attempt to better understand the physics governing the apparition of reverse-light-induced excited spin state trapping (LIESST) phenomena in spin crossover (SCO) compounds, we have studied the LIESST effect and the possibility of a reverse-LIESST effect in the SCO complex Zn_1−xFex(6-mepy)₃tren(PF₆)₂·CH₃CN, x = 0.5%. ((6-mepy)₃tren = tris{4-[(6-methyl)-2-pyridyl]-3-aza-butenyl}amine)). This complex was chosen as a good candidate to show reverse-LIESST by comparison with its unsolvated analogue, since the introduction of acetonitrile in the structure leads to the stabilisation of the high-spin state and both exhibit a very abrupt thermal spin transition. Indeed, the steep thermal spin transitions of two differently polarised crystals of Zn_1−xFex(6-mepy)₃tren(PF₆)₂·CH₃CN, x = 0.5% have been characterised in detail in a first step using absorption spectroscopy and no influence of the polarisation was found. These were then fitted within the mean field model to obtain the variation in the enthalpy and entropy and the critical temperatures associated with the process, which are significantly lower with respect to the unsolvated compound due to the incorporation of acetonitrile. In a second step, the light-induced low-spin-to-high-spin transition at low temperatures based on LIESST and its subsequent high-spin-to-low-spin relaxation at different temperatures were characterised by time-resolved absorption spectroscopy, with exponential behaviour in both cases. The stabilisation of the high-spin state due to the presence of acetonitrile was evidenced. Finally, light-induced high-spin-to-low-spin state transition at low temperature based on reverse-LIESST was attempted by time-resolved absorption spectroscopy but the Fe(II) concentration was too low to observe the effect. Full article

Laser ablated Be atoms have been reacted with acetonitrile molecules in 4 K solid neon matrix. The diberyllium products BeBeNCCH₃ and CNBeBeCH₃ have been identified by D and ¹³C isotopic substitutions and quantum chemical calculations. The stabilization of the diberyllium species is rationalized from the formation of the real Be−Be single bonds with bond distances as 2.077 and 2.058 Å and binding energies as −27.1 and −77.2 kcal/mol calculated at CCSD (T)/aug-cc-pVTZ level of theory for BeBeNCCH₃ and CNBeBeCH₃, respectively. EDA-NOCV analysis described the interaction between Be₂ and NC···CH₃ fragments as Lewis “acid−base” interactions. In the complexes, the Be₂ moiety carries positive charges which transfer from antibonding orbital of Be₂ to the bonding fragments significantly strengthen the Be−Be bonds that are corroborated by AIM, LOL and NBO analyses. In addition, mono beryllium products BeNCCH₃, CNBeCH₃, HBeCH₂CN and HBeNCCH₂ have also been observed in our experiments. Full article

The reactions of alkenes with phenyl-N-triflylimino-λ³-iodane PhI=NTf (1) have been studied in different conditions. In methylene chloride, in the presence of N-halosuccinimides, the products of mono and bis-triflamidation were obtained. In MeCN, the product of bromotriflamidation (with NBS) with solvent interception or of bis-triflamidation (with NIS) is formed. The reaction with trans-stilbene in acetonitrile with NBS gave rise to cyclization to 2-methyl-4,5-diphenyl-1-triflyl-4,5-dihydro-1H-imidazole. In contrast, with NIS as an oxidant, both in CH₂Cl₂ and MeCN, the major product was 2,3-diphenyl-1-triflylaziridine formed in good yield. With NBS, aziridine is also formed but as a minor product, the major one being a mixture of diastereomers of the product of bromotriflamidation. The reaction of compound 1 with vinylcyclohexane in methylene chloride affords the mixtures of regioisomers of the products of halotriflamidation, whereas in acetonitrile, the products of solvent interception and cyclization to the imidazoline are formed. A mechanism explaining the formation of all isolated products is proposed. Full article

Electrochemical oxidation of 1-R-substituted silatranes 1 (R = Me, vinyl, (CH₂)₂CN, CH₂Ph, CH₂(C₁₀H₇), Ph, C₆H₄Me, p-Cl-C₆H₄, Cl)—classical representatives of pentacoordinated silicon compounds—and the formation of their short living cation radicals upon reversible or quasi-reversible one-electron withdrawal were studied by means of cyclic and square-wave voltammetry, faradaic impedance spectroscopy and real-time temperature-dependent EPR spectroelectrochemistry supported by DFT B3PW91/6-311++G(d,p) (C-PCM, acetonitrile) calculations. The main reaction responsible for the decay of 1^+• is shown to be their deprotonation, and ways of increasing the stability of these species are proposed. Full article

Aim: Bosutinib (BST) is an anti-cancer medicine that is used to treat a variety of different types of cancer. Using the HPLC method of analysis and the Quality by Design (QbD) strategy, the study aimed to precisely quantify the drug in tablet form and in rat plasma. Methodology: For the developed method’s validation, the chromatographic settings were fine-tuned by making use of the Box–Behnken Design (BBD). In the BBD, two dependent variables and three independent variables were selected. Isocratically, samples were eluted, having eluent phase composition of ammonium acetate (CH₃COONH₄) buffer pH 3.0 and acetonitrile (CH₃CN) (60:40% v/v), in Raptor C-18 column at temperature 25 ${}^{\circ }$C with a flow rate of 1 mL/min for 5 min. The wavelength of detection was set at 260 nm. In this study, encorafenib (ENC) was employed as an internal standard. Result: A sharp and resolved peak of BST and ENC at a retention time of 1.92 min and 4.01 min, respectively, was observed by the developed method. The limits of quantification and detection of the newly established method were found to be 1.503 $\mathsf{\mu }$g/mL⁻¹ and 0.496 $\mathsf{\mu }$g/mL⁻¹. The calibration curve’s observed linearity range was between 2 and 20 $\mathsf{\mu }$g/mL⁻¹, with an r² of 0.999. The developed and optimized method was verified in compliance with the ICH guidelines. The results of all validation parameters were within the acceptable range, for example, % RSD of system suitability (0.63–4.46), % RSD of linear regression (1.659), interday and intraday precision % RSD value (1.723–1.892), and (1.762–1.923), respectively, and accuracy (1.476–1.982). Conclusion: The quantity of BST in tablet dosage form and in rat plasma samples was determined using a simple, quick, and robust method that was devised and validated. Full article

We investigate the corrosion behavior on the microstructure of CoCrFeMnNi high-entropy thin film potentiodynamic alloys electrodeposited on aluminum support. Using electrolytes based on dimethyformamide (DMF), (HCON(CH₃)₂), dimethylsulfoxide (DMSO, (CH₃)₂SO), an acetonitrile (AN, CH₃CN) organic system (4:1 vol. ratio), LiClO₄ in different concentrations and CoCl₂, CrCl₃ × 6H₂O, FeCl₂ × 4H₂O, MnCl₂ × 4H₂O and NiCl₂ × 6H₂O in different conditions, the HEA components were co-deposited on an aluminum foil substrate. Using the CALPHAD method and the MatCalc PC software, the structure of the HEA system under study was investigated by calculating the characteristic kinetic and thermodynamic criteria. The influence of each metal from HEA inside the solid solution zone and over the formation of the solid solution phase were obtained from the ratio between the derived parameters. The electrochemical measurements, which demonstrate that on an aluminum support the HEA thin films have lower corrosion resistance, were performed at ambient temperature in an aerated artificial solution. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to investigate the microstructure of HEA thin films before and after corrosion in artificial seawater. This complex study demonstrates that the electrodeposition of HEA thin films on an aluminum support is more difficult and that the resistance to corrosion is much lower compared to that in the previous work on HEA deposits on a copper support. Full article

A theoretical modelling of the interaction process between a protonated complex of carboxonium derivative [2,6-B₁₀H₈O₂CCH₃*H^fac]⁰ and acetonitrile molecule CH₃CN was carried out. As a result of the process, a trisubstituted [B₁₀H₇O₂CCH₃(NCCH₃)]⁰ derivative was formed. This reaction has an electrophile-induced nucleophilic substitution (EINS) mechanism. The main intermediates and transition states of the substitution process were established. As in the case of all previously investigated EINS processes, the key intermediate was an anion with a dihydrogen H₂ fragment attached to one boron atom (B(H₂) structure motif). The process of nucleophilic substitution can proceed on a different position of the cluster cage. The main potential pathways were assessed. It was established that substitution on the B₄ position of the cluster cage was the most energetically favourable, and the [2,4,6-B₁₀H₇O₂CCH₃(NCCH₃)]⁰ isomer was formed. Full article

Diiron μ-aminocarbyne complexes [Fe₂Cp₂(NCMe)(CO)(μ-CO){μ-CN(Me)(R)}]CF₃SO₃ (R = Xyl, [1a^NCMe]CF₃SO₃; R = Me, [1b^NCMe]CF₃SO₃; R = Cy, [1c^NCMe]CF₃SO₃; R = CH₂Ph, [1d^NCMe]CF₃SO₃), freshly prepared from tricarbonyl precursors [1a–d]CF₃SO₃, reacted with NaOCN (in acetone) and NBu₄SCN (in dichloromethane) to give [Fe₂Cp₂(kN-NCO)(CO)(μ-CO){μ-CN(Me)(R)}] (R = Xyl, 2a; Me, 2b; Cy, 2c) and [Fe₂Cp₂(kN-NCS)(CO)(μ-CO){μ-CN(Me)(CH₂Ph)}], 3 in 67–81% yields via substitution of the acetonitrile ligand. The reaction of [1a^NCMe–1c^NCMe]CF₃SO₃ with KSeCN in THF at reflux temperature led to the cyanide complexes [Fe₂Cp₂(CN)(CO)(μ-CO){μ-CNMe(R)}], 6a–c (45–67%). When the reaction of [1a^NCMe]CF₃SO₃ with KSeCN was performed in acetone at room temperature, subsequent careful chromatography allowed the separation of moderate amounts of [Fe₂Cp₂(kSe-SeCN)(CO)(μ-CO){μ-CN(Me)(Xyl)}], 4a, and [Fe₂Cp₂(kN-NCSe)(CO)(μ-CO){μ-CN(Me)(Xyl)}], 5a. All products were fully characterized by elemental analysis, IR, and multinuclear NMR spectroscopy; moreover, the molecular structure of trans-6b was ascertained by single crystal X-ray diffraction. DFT calculations were carried out to shed light on the coordination mode and stability of the {NCSe-} fragment. Full article

The reactions of the diiron aminocarbyne complexes [Fe₂Cp₂(NCMe)(CO)(μ-CO){μ-CN(Me)(R)}]CF₃SO₃ (R = Me, 1a^NCMe; R = Cy, 1b^NCMe), freshly prepared from the tricarbonyl precursors 1a–b, with primary amines containing an additional function (i.e., alcohol or ether) proceeded with the replacement of the labile acetonitrile ligand and formation of [Fe₂Cp₂(NH₂CH₂CH₂OR’)(CO)(μ-CO){μ-CN(Me)(R)}]CF₃SO₃ (R = Me, R’ = H, 2a; R = Cy, R’ = H, 2b; R = Cy, R’ = Me, 2c) in 81–95% yields. The diiron-oxazolidinone conjugate [Fe₂Cp₂(NH₂^OX)(CO)(μ-CO){μ-CN(Me)₂}]CF₃SO₃, 3, was prepared from 1a, 3-(2-aminoethyl)-5-phenyloxazolidin-2-one (NH₂^OX) and Me₃NO, and finally isolated in 96% yield. In contrast, the one pot reactions of 1a-b with NHEt₂ in the presence of Me₃NO gave the unstable [Fe₂Cp₂(NHEt₂)(CO)(μ-CO){μ-CN(Me)(R)}]CF₃SO₃ (R = Me, 4a; R = Cy, 4b) as unclean products. All diiron complexes were characterized by analytical and spectroscopic techniques; moreover, the behavior of 2a–c and 3 in aqueous media was ascertained. Full article