Ring Oxygen Atom Research Articles

Mechanisms of interface electrostatic potential induced asphalt-aggregate adhesion

The electrostatic potential at the interface of the asphalt molecular and aggregate oxides is the primary factor generating the adhesion between the asphalt-aggregate contact surfaces. However, the route of electrostatic potential affecting the asphalt-aggregate adhesion is yet to be determined at the molecular level. This study proposed that the electron accumulation at the interface of the asphalt molecular and aggregate oxides generates a significant electrostatic potential hence to induce the adhesion between the asphalt and aggregate in asphalt pavement. A microscopic molecular dynamics (MD) simulation incorporated with macroscopic adhesion work experiments is conducted to analyze the interface adhesive performance between the asphalt and aggregate. The adhesion work experiment demonstrated the effect of aggregate surface oxides on asphalt adhesion at the macro level and further verified the simulation results. The result demonstrated that a notable electron accumulation can be observed by MD at the interface of asphalt molecular and multiple oxides which generates the electrostatic potential. The strong electrostatic attractions and hydrogen bonds between alkaline oxides (MgO, CaO, CaCO3) and asphalt molecules enhance the relative concentration distribution, diffusion coefficient, and adhesion of asphalt on the aggregate surface. The significant electrostatic potential difference at the interface of the asphalt molecular and the oxide enables a strong adhesion between them due to the near-surface failure potential. Besides, the negative charge accumulation on both the benzene ring structure and oxygen atoms in the asphalt molecules results in poor adhesion at the interface of asphalt molecules and multiple oxides. It was found that a high correlation exists between the MD prediction and experimental testing results. Thus, this research provides a valuable tool for guiding the pairing and selection of asphalt with various minerals for pavement design, construction, and maintenance agencies.

Modular Access to Functionalized Oxetanes as Benzoyl Bioisosteres.

Bioisosterism is a valuable principle exploited in drug discovery to fine-tune physicochemical properties of bioactive compounds. Functionalized 3-aryl oxetanes, as an important class of bioisosteres for benzoyl groups (highly prevalent structures in approved drugs), have been rarely utilized in agrochemicals and pharmaceuticals due to significant synthetic challenges. Here, we present a modular synthetic strategy based on the unexplored yet readily available reagents, oxetanyl trichloroacetimidates, inspired by Schmidt glycosylation, enabling easy access to a library of functionalized oxetanes. This operationally simple protocol leverages the vast existing libraries of aryl halides and various nucleophiles. The power and generality of this approach is demonstrated by late-stage functionalization of complex molecules, as well as the rapid synthesis of oxetane analogues of bioactive molecules and marketed drugs. Preliminary mechanistic study suggests that the oxygen atom in the oxetane ring plays a crucial role in stabilizing the carbocation intermediates.

Synthesis, structural investigations, in vitro cytotoxicity, apoptotic activity, cell cycle analysis, and molecular modeling studies of nano‐sized Zn(II) Schiff base complex

A new novel tetradentate ligand, [(1E,1′E)‐N,N′‐(1,2‐phenylene)bis(1‐(5‐(2‐fluorophenyl)furan‐2‐yl)methanimine) (PFPFMI), and its nano‐sized [Zn(PFPFMI)Cl2].3H2O complex were synthesized. The geometry of PFPFMI and its Zn(II) complex was described through CHN analyses, Fourier‐transform infrared spectroscopy (FTIR), UV–visible, X‐ray diffraction (XRD), thermal gravimetric analysis (TGA), and mass spectral data tests. The spectral data of the nano‐sized [Zn(PFPFMI)Cl2].3H2O complex indicates that the PFPFMI ligand functions as a tetradentate (N2O2) coordination through two azomethine nitrogen groups (N) and two furan ring oxygen (O) atoms. Density functional theory (DFT) calculations were performed using the molecular studio software to investigate the optimal geometry of PFPFMI and its [Zn(PFPFMI)Cl2].3H2O complex. The SEM, TEM, XRD, AFM, and energy dispersive X‐ray analysis (EDX) analyses of the studied complex unveil distinct and strong diffraction peaks, indicating its crystalline nature and providing evidence of its nano‐sized particle sizes. Additionally, the inhibition zone diameter was used to assess the in vitro antimicrobial action of PFPFMI and the particular complex against Gram‐positive bacteria Streptococcus pneumonia and Bacillus subtilis, Gram‐negative bacteria Pseudomonas aeruginosa, Salmonella typhi, and Escherichia coli, as well as fungi Aspergillus fumigatus, Geotricum candidum, Syncephalastrum racemosum, and Candida tropicalis. The [Zn(PFPFMI)Cl2].3H2O complex exhibits higher activity than the ligand PFPFMI. In vitro cytotoxicity of the synthesized [Zn(PFPFMI)Cl2].3H2O complex was explored using MCF7 (breast cancer), HCT116 (colon cancer), A549 (lung cancer), HePG‐2 (liver cancer), A375 (melanoma cancer), and normal lung fibroblast (WI38) cell lines. Based on IC50 and selective index (SI) values, it was shown that the complex exhibited higher potency against MCF7 cell lines. Moreover, the Zn(II) complex exhibited the ability to induce DNA damage in MCF7 cells, resulting in dose‐dependent cell apoptosis. Subsequent investigations revealed that complex 2 also induced cell cycle arrest in the G2 and S phases.

Removal of caffeine from aqueous and vacuum environments using Si12C12, Si11GeC12, Si11BC12 fullerenes: A DFT and TDDFT studies

Caffeine (CFI) adsorption upon the perfect, boron-doped (Si11BC12 and Si12BC11), and germanium-doped (Si11GeC12 and Si12GeC11) silicon carbide (SiC) fullerenes have been studied to assess the feasibility of caffeine removal from aqueous and vacuum environments by using density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The adsorption energy and charge transfer of caffeine through its nitrogen atom of the imidazole ring upon the surface of Si12C12 nano-cage is stronger than that of the oxygen atoms of the pyrimidinedione ring with moderate adsorption energy. The theoretical infrared (IR) spectrum shows that the vibrational frequency of CFI changes after interacting with the pure Si12C12 fullerene, and this change is comparable to the experimental data. According to the TDDFT method, Ultraviolet–Visible (UV–Vis) techniques reveal that the optical features of the pure, Si11BC12, Si11GeC12 fullerenes changed after interacting with CFI. The density of state (DOS) analysis confirmed that the caffeine adsorption via imidazole ring with a robust electron hybridization can be remarkably altered the electronic features of Si12C12 fullerene, being too sensitized to the binding of caffeine. The results demonstrate that CFI adsorption on Si12C12 is stronger than on Si11BC12 and Si11GeC12 fullerenes. The presence of a boron (B) atom in the Si11BC12 fullerene improves the dipole moment and optical properties as compared to the Si11GeC12 fullerene. Upon caffeine adsorption, the Si12C12 and Si12BC11 fullerenes could be promising adsorbents for caffeine removal and detection because of the strong interaction, increasing dipole moment, and short recovery time.

Structure elucidation {single X-ray crystal diffraction studies, Hirshfeld surface analysis, DFT} and antibacterial studies of 1,2-benzothiazine metal complexes

The 2-benzyl-4‑hydroxy-1,1-dioxo-1,2-benzothiazine-3-carboxylic acid methyl ester i.e., ligand 1 was utilized to synthesize Mn(II) 2, Co(II) 3, Ni(II) 4, Cu(II) 5 and Zn(II) 6 derived metal complexes in mild basic conditions. The structural investigation was carried out by UV–vis, FT-IR, NMR spectroscopy, CHN analysis, conductivity measurement, ESI-MS analysis and magnetic susceptibility techniques. The X-ray diffraction analysis confirmed the octahedral and distorted square pyramidal geometries of the cobalt and copper complexes. The ligand 1 coordinated with metal centres through enolic oxygen atoms of the thiazine ring and ester group while methanol coordinated with metal center via oxygen atom. The Hirshfeld surface analysis (HSA) was utilized to determine the intermolecular interactions. In support of the experimental data, DFT studies were also performed for the cobalt and copper complexes. The NBO analysis resulted in the large stabilization values 11.91 and 12.35 kcal/mol for the cobalt and copper complexes. The global reactivity indicated the higher values of hardness and the large values of FMO analysis which support the higher stability of the metal complexes. The synthesized compounds were also evaluated against six bacterial strains to check their antibacterial potential. It was observed from results that highest activity was depicted by copper complex 5 against B. subtilis and the zone of inhibition is 23.4 ± 0.6 mm which is comparable to ampicillin (standard drug).

Recent Advances Related to Anomeric and Exo-anomeric Effects in Carbohydrate Chemistry

The anomeric effect in carbohydrate chemistry is known as the interaction between the OHd substituent at the anomeric position to favor an axial orientation rather than an equatorial one, despite the increased 1,3-diaxial interactions. In the anomeric effect, a sugar ring is stabilized by an electronegative substituent at the C1 carbon, also known as the anomeric carbon. The stabilization is thought to result from interactions between lone electron pairs on oxygen and a C1 antibonding orbital. On the other hand, the anomeric effect can be of two types: endo-anomeric and exo-anomeric. The effect is called endo-anomeric when the lone pair comes from the oxygen atom in the sugar ring and exo-anomeric when the lone pair comes from oxygen in a substituent on C1. Several factors influence the anomeric effect. In this way, this review aims to describe the recent advances in main theories, observations, and advances achieved in the last decades related to the anomeric effect.
 GRAPHICAL ABSTRACT

2-Oxoquinoline-based-thiosemicarbazones as multitargeting neurotherapeutics against Alzheimer's disease: In vitro and in silico studies of MAO and ChE inhibitors.

Alzheimer's disease (AD) presents a multifactorial neurological disorder with multiple enzyme involvement in its onset. Conventional monotherapies fall short in providing long-term relief, necessitating the exploration of alternative multitargeting approaches to address the complexity of AD. Therefore, the design, synthesis, and in vitro and in silico evaluation of 2-oxoquinoline-based thiosemicarbazones 9a-r as multipotent analogs, able to simultaneously inhibit the cholinesterase (ChE) and monoamine oxidase (MAO) enzymes for the potential treatment of AD, are reported. In the in vitro experimental evaluation of MAO and ChE inhibition, all tested compounds demonstrated remarkable potency exhibiting nonselective inhibition of both MAO-A and MAO-B, and selective inhibition of acetylcholinesterase (AChE) over butyrylcholinesterase (BChE), with 9d, 9j, and 9m evolving as lead compounds for MAO-A, MAO-B, and AChE, displaying IC50 values of 0.35 ± 0.92, 0.50 ± 0.02, and 0.25 ± 0.13 μM, respectively. Moreover, the kinetic studies revealed that all tested compounds inhibited all three enzymes through a competitive mode of inhibition. Furthermore, the molecular docking studies of the most active compounds revealed several crucial interactions, particularly hydrogen bonding interactions. These interactions were observed between the nitrogen and sulfur atoms of thiosemicarbazone and the nitrogen and oxygen atoms of the quinoline ring with various amino acids, suggesting the strong interactions of these compounds with the enzymes.

The interaction of triglycidyl phosphate with europium nitrate and properties of obtained metal-containing polymer

The interaction of phosphorus-containing epoxy trifunctional monomer – triglycidyl phosphate (TGPhT), with europium (III) nitrate hexahydrate is studied. A dissolution of europium salt added into TGPhT is occurred due to the interaction of the cation with phosphoryl groups and oxygen atoms of the epoxy ring, that is accompanied by the opening reaction and led to the formation of a polymer. The interaction of triepoxide with salt is investigated by FTIR-spectroscopy and differential scanning calorimetry (DSC). The thermal stability of the samples is determined by combined method of thermogravimetry and differential scanning calorimetry (TG/DSC), coupled with a quadrupole mass spectrometry to identify the gaseous products evolved during the thermal analysis of the samples. The kinetic parameters of the curing reaction are computed by using Thermokinetics software. The interaction of TGPhT with europium nitrate is suggested to occur through opening of epoxy rings in the presence of europium ions via the mechanism of cationic polymerization. The cured epoxy polymer exhibits luminescent properties.

4-(4-methoxyphenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazin-5(6H)-one: Synthesis, crystal structure, Hirshfeld surface analysis, noncovalent, ADMET studies and biological evaluation

Oxadiazines are heterocyclic compounds containing two nitrogen and one oxygen atom in a six-membered ring. The synthesis and crystal structure of 4-(4-methoxyphenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazin-5(6H)-one (MPMP-OXA) was reported. The organic crystal structure of the synthesized compound was fully characterized by various spectroscopic techniques (Fourier Transform Infrared Spectroscopy, NMR and LC/MS-TOF) and single-crystal X-ray diffraction studies. The MPMP-OXA crystal structure crystallizes in the triclinic system and space group P-1 with a = 5.9395(15) Å, b = 11.471(3) Å, c = 11.901(3) Å, α = 70.075(4)°, β = 83.454(4)°, γ = 78.016(4)°, V = 744.9(3) Å3, Z = 2 cell parameters. This work is aimed to study the weak interactions in the crystal packing of a new synthesized oxadiazine derivate. The contributions of the most important intermolecular interactions in the crystal structure were investigated by 3D-Hirshfeld surface (HS) and 2D-fingerprint analysis. The CH···O interactions as the most important contributors to the crystal packing between the oxygen of the oxadiazine ring and the hydrogen atom of phenyl ring appear as bright red spots visible on the HS surface. The hydrogen-bonded interaction of MPMP-OXA has been investigated using noncovalent interactions approach. The molecular docking studies for the synthesized compound were performed to gain insight into the inhibition nature of this molecule against DNA Gyrase B Candida and 3-chymotrypsin-like protease (SARS-CoV main protease) proteins and resulted in good activities for new anti-agents. Lastly, Bioavailability, druggability as well as absorption, distribution, metabolism, excretion, and toxicity parameters (ADMET), and gastrointestinal absorption (BOILED-Egg method) properties of newly synthesized compound using smile codes were performed in detail.

Pathway exploration in low-temperature oxidation of a new-generation bio-hybrid fuel 1,3-dioxane

The joint and flexible utilization of renewable electricity, ligno-cellulosic biomass, and/or CO2 point sources to produce so-called bio-hybrid fuels is a promising solution to achieve carbon neutrality while still meeting the energy demand of the transportation sector. One of the new-generation bio-hybrid fuels is 1,3-dioxane. It has a special chemical structure with two oxygen atoms in a six-membered ring. In this work, the low-temperature oxidation of 1,3-dioxane was studied theoretically and experimentally. Potential energy surfaces of the products of the O2 recombination with the three radicals formed from the H-atom abstraction of 1,3-dioxane were calculated at the DLPNO-CCSD(T)/CBS//B2PLYP-D3/cc-pVTZ level. The reaction rate coefficients were calculated with the RRKM/master equation method (T = 500–2000 K, p = 0.01–100 atm). To validate the proposed pathways, low-temperature oxidation experiments of 1,3-dioxane were performed in a jet stirred reactor (JSR) coupled with a synchrotron photon ionization time of flight molecular beam mass spectrometer (T = 590 K, p = 1 bar). Key intermediates in the investigated pathways were captured and identified by the combination of measured photon ionization efficiency curves and calculated ionization energies. Compared to cyclohexane, which has no oxygen in the six-membered ring, 1,3-dioxane has much weaker C-H bonds for the carbon between the two oxygen atoms, thus enabling faster internal H-atom migration from ROO to QOOH. Furthermore, oxidation of 1,3-dioxane tends to favor cyclic ethers + OH (chain propagation) instead of alkenes + HO2 (chain termination), explaining its high reactivity in the low-temperature regime.

Experimental and Computational Studies on the Biotransformation of Pseudopyronines with Human Cytochrome P450 CYP4F2.

The secondary metabolite pseudopyronine B, isolated from Pseudomonas mosselii P33, was biotransformed by human P450 enzymes, heterologously expressed in the fission yeast Schizosaccharomyces pombe. Small-scale studies confirmed that both CYP4F2 and CYP4F3A were capable of oxidizing the substrate, with the former achieving a higher yield. In larger-scale studies using CYP4F2, three new oxidation products were obtained, the structures of which were elucidated by UV-vis, 1D and 2D NMR, and HR-MS spectroscopy. These corresponded to hydroxylated, carboxylated, and ester derivatives (1-3) of pseudopyronine B, all of which had been oxidized exclusively at the ω-position of the C-6 alkyl chain. In silico homology modeling experiments highlighted key interactions between oxygen atoms of the pyrone ring and two serine residues and a histidine residue of CYP4F2, which hold the substrate in a suitable orientation for oxidation at the terminus of the C-6 alkyl chain. Additional modeling studies with all three pseudopyronines revealed that the seven-carbon alkyl chain of pseudopyronine B was the perfect length for oxidation, with the terminal carbon lying close to the heme iron. The antibacterial activity of the substrates and three oxidation products was also assessed, revealing that oxidation at the ω-position removes all antimicrobial activity. This study both increases the range of known substrates for human CYF4F2 and CYP4F3A enzymes and demonstrates their utility in producing additional natural product derivatives.

Solvation of dibenzo-18-crown-6 ether in water-aprotic solvents

The Gibbs free energies of transfer of dibenzo-18-crown-6 ether from dimethyl sulfoxide and N,N-dimethylformamide to their mixtures with water (ΔtrG0(DB18C6)solv→χW) were determined by the interphase distribution method. The enthalpies of dissolution of DB18C6 were determined by the calorimetric method at 25.00 ± 0.01 °C. The analysis of the influence of solvent composition and properties on the thermodynamic characteristics of DB18C6 solvation was carried out. It was found that a change in the solvent composition in both cases does not lead to significant changes in the crown ether solvation state. A compensation effect in enthalpy and entropy contributions to ΔtrG0(DB18C6) was observed. It has been shown that the priority contribution to the change in the thermodynamic characteristics of DB18C6 solvation is made by the resolvation of the crown ring oxygen atoms. The resolvation of DB18C6 occurs at χW > 0.6 mol fr. Proper data are compared with data reported in the literature.

Structural analysis of dexrazoxane: Exploring tautomeric conformations

Structural analysis of dexrazoxane, as a cardioprotective agent, was done in this work by exploring formations of tautomeric conformations and investigating the corresponding effects. Density functional theory (DFT) calculations were performed to optimize the structures to evaluate their molecular and atomic descriptors. In addition to the original structure of dexrazoxane, eight tautomers were obtained with lower stability than the original compound. Movements of two hydrogen atoms in between nitrogen and oxygen atoms of heterocyclic ring put such significant effects. Moreover, electronic molecular orbital features showed effects of such tautomerism processes on distribution patterns and surfaces, in which evaluating the quadrupole coupling constants helped to show the role of atomic sites for resulting the features. As a consequence, the results indicated that the tautomeric formations could significantly change the features of dexrazoxane reminding the importance of carful medication of this drug for patients.

Cyanide Anion Determination Based on Nucleophilic Addition to 6-[(E)-(4-Nitrophenyl)diazenyl]-1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole] Derivatives

This work provides a novel approach for the instant detection of CN− anions based on chromogenic 6-[(E)-(4-nitrophenyl)diazenyl]-1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole] derivatives. New colorimetric detectors were synthesized and characterized. These compounds exhibited a substantial color change from orange to magenta and blue when treated with cyanide ions in a CH3CN solution buffered with sodium phosphate and demonstrated high selectivity to CN− anions. Common anions were tested, and they did not interfere with cyanide detection, except for carbonates and hydrosulfites. The simple preparation of a molecular sensor and the easily noticeable color change makes this a practical system for the monitoring of CN− ions. This color change is explained by nucleophilic substitution of the pyrane ring oxygen atom at the indoline C-2 atom by the cyanide anion. This generates the appearance of intensively colored 4-(4-nitrophenylazo)phenolate chromophore and allows for determining very low levels of CN− anion.

Evidence for supramolecular catalysis in the synthesis of cyclic organic carbonates over zeolite Y impregnated with metal iodides

• Styrene carbonate was produced over zeolite Y impregnated with KI. • The conversion and selectivity increase with the loading of impregnated KI. • Calculations showed the epoxide attack by iodide as the rate-determining step. • Calculations indicated a perfect fit of the transition state inside the zeolite cage. • Results were consistent with an enzyme-like behavior in accelerating the reaction. The reaction of epoxides with CO 2 to afford cyclic organic carbonates was studied over zeolite Y impregnated with metal iodides. The experimental results indicated that formation of styrene carbonate is significantly higher on zeolite Y impregnated with KI compared to KI alone. The conversion and selectivity increase with the loading of impregnated KI on the zeolite, although the epoxide/iodide molar ratio were in the range of 86 to 220, among the highest ever reported for this reaction. A periodical DFT study indicated that metal halides are stabilized upon embedding inside the zeolite Y cavity and interact with the framework counter cations. The theoretical study of the reaction pathway, considering the CO 2 cycloaddition to ethylene oxide as model, indicated that the opening of the epoxide ring is the rate-determining step, in agreement with the experimental results that showed a correlation between conversion and the KI loading. The energy of activation is lower on the zeolite/metal halide systems, explaining the higher activity of the metal halides when embedded within the zeolite cavity. The calculations indicated that the reaction occurs on two opposite framework aluminum sites having the embedded metal halide between them. Whereas the epoxide interacts with the framework counter cation of one site, the metal iodide interacts with the counter cation of an opposite site, providing the perfect alignment for the nucleophilic attack and leading to the preferred geometry for the transition state, which resembles a S N 2 type mechanism, with nucleophilic attack of the iodide occurring on the opposite side of the ring oxygen atom. This remarkable behavior is characteristic of enzymatic reactions and stresses the importance of host-guest supramolecular catalysis occurring on zeolitic systems. Graphical Abstract .

Highly Stereoselective Asymmetric Total Synthesis of (−)-Jimenezin via Sequential Intramolecular Amide Enolate Alkylation

A highly stereoselective asymmetric total synthesis of (-)-jimenezin (1), a potent anticancer acetogenin, was efficiently completed with the key feature being a sequential intramolecular amide enolate alkylation (IAEA). Our investigation to probe the origin of the complete stereoselectivity in the second IAEA step to form the conformationally flexible tetrahydrofuran with perfect stereocontrol identified the presence of the oxygen atom in the adjacent tetrahydropyran ring to be crucial.

Iron(III) and copper(II) complexes derived from the flavonoids morin and quercetin: Chelation, crystal structure and DFT studies

The [Fe(morin)3] structure represents the first example of a single-crystal x-ray structure of any metal ion coordinated to a flavonoid. In this case it is iron(III) coordinated to three equivalents of morin via chelation producing a distorted octahedral coordination geometry around the iron centre. The crystals were successfully grown from a mixture of toluene and ethyl acetate. The complex crystallizes in a monoclinic space group P21/c, with coordination via the carbonyl and hydroxy oxygen atoms of morin's ring C. There was disorder with the solvent molecules and these were squeezed out using the program SQEEZE. The experimental studies were supported by relative energy and electron density distributions of the associated complexes predicted by Density Functional Theory calculations performed at the M06-2X/def2-SVP level of theory.Furthermore, the Job's plots (method of continuous variance) method was used to establish the stoichiometry of both quercetin and morin with the metal ions copper(II) and iron(III). Copper(II) shows a stoichiometry of 1:2 for both flavonoids and iron(III) shows a stoichiometry of 1:3 for both which is in agreement with the crystal structure which has been obtained. The synthesized chelating complexes were characterized by FT-IR, mass spectrometry and microanalyses.

Hygroscopic metal-organic framework MIL-160(Al): In-situ time-dependent ATR-FTIR and gravimetric study of mechanism and kinetics of water vapor sorption

Metal-organic frameworks (MOFs) are advanced highly porous coordination polymers of high interest to separations, environmental remediation, catalysis, and biomedicine. While many MOFs are unstable in water and aqueous solutions, aluminum MOFs (Al-MOFs) offer an unprecedented stability. First, we synthesize unusual highly hygroscopic Al-MOF MIL-160(Al), purify it and assign FTIR peaks to specific groups as potential water binding sites. Further, we introduce a novel method of in-situ time-dependent ATR-FTIR spectroscopy to detect specific binding sites in MIL-160(Al) and investigate the progress of reaction. Specifically, we combine in-situ time-dependent ATR-FTIR spectroscopy with using water as “spectroscopic probe” to determine binding sites in MIL-160(Al) and their evolution during the reaction. The in-situ time-dependent ATR-FTIR spectra provide evidence of water bonding to: the μ-OH group, the carboxylate anion COO– in 2,5-FDCA2- linker, oxygen atom in the furan ring of the linker, and the C–C and C–H bonds of the furan ring of the linker. Then, we conduct mechanistic and kinetic study of sorption of water vapor on MIL-160(Al) in air using the combination of two complementary in-situ time-dependent methods: the ATR-FTIR spectroscopy and gravimetric analysis. Water vapor sorption on MIL-160(Al) results in the solid-state adsorption complex with up to four water molecules per unit of MIL-160(Al). Chemical kinetics of water sorption on MIL-160(Al) follows a pseudo-first order rate law and it is consistent with dynamics and timescale revealed by in-situ time-dependent ATR-FTIR. The combination of two in-situ time-dependent methods, the ATR-FTIR spectroscopy and gravimetry, forms a new powerful experimental approach to facilely study mechanisms, stoichiometry and chemical kinetics of various solid–gas reactions in the ambient and controlled environments.

Computational study for the electrophilic reactivity prediction of crown ethers

Crown ethers are kinds of macrocyclic compounds with high selectivity to metal cations, which can be used as ion sensors, ion analytical reagents and ionophores for biological applications. The chemical reactivity of 1,8-dihydroxyl-4,4,5,5-tetramethylbenzo-14-crown-4 had been investigated at the level of M062X/def2TZVP with Gauss16. The conformations were studied though the high-temperature annealing process with Gromacs. The applicability of Frontier molecular orbital theory, Conceptual density functional theory and Molecular electrostatic potential analysis for the reactivity prediction were discussed. The analysis results show that the methods reflecting the electronic softness property such as Fukui function, global softness, relative nucleophilicity, are suitable for the prediction of electrophilic substitution reaction sites. The electrophilic substitution reaction sites of different conformations are at the C25 or C26 atom, which has the largest HOMO orbital compositions. The oxygen atoms of the main ring and the hydroxyl groups are the binding sites of metal cations. The lowest electrostatic potential is −74.81 kcal/mol on the vdW surface of (1R, 8S) 1,8-dihydroxyl-4,4,5,5-tetramethylbenzo-14-crown-4 contributing to the lone pair electrons and π-electron cloud. The hydroxyl groups and the benzene ring can decrease the surface potential and increase the reactivity.

Preparation of thermally stable magnetic poly(urethane-imide)/nanocomposite containing β-cyclodextrin cavities as new adsorbent for lead and cadmium

In this work, the thermally stable magnetic poly(urethane-imide) nanocomposite (β-CDPUIm-MNPs (9)) was prepared by reaction of β-cyclohexatriene with diisocyante (5) as a new synthetic cross linker agent and its adsorption behavior for removal of heavy metal ions from water was examined and compared with bare poly(urethane-imide). This poly(urethane-imide) based nanocomposite was employed for the removal of Pb(II) and Cd(II) metals from the waste water for the first time and it has proved to have an excellent efficiency probably due to the presence of nitrogen and oxygen atoms in the imide ring. β-CDPUIm-MNPs (9) displayed highly effective adsorption performance to lead and cadmium and showed maximum adsorptions during 20 min. For optimization of lead and cadmium ions adsorption, the effects of different factors like pH, contact time, and initial amounts of Pb(II) and Cd(II) ions were studied. Results showed that pH has a great influence on the adsorption behavior and also maximum adsorption capacity was obtained at pH 7. Examination of the isotherm and adsorption kinetics showed that equilibrium adsorptions and kinetic are well-modeled by applying Langmuir isotherm model and pseudo-second-order kinetics, respectively. The maximum adsorption capacities of β-CDPUIm-MNPs (9) for Pb(II) and Cd(II) ions based on Langmuir isotherm calculation were 344.830 and 303.030 mg/g, respectively. Regenerated β-CDPUIm-MNPs (9) were used as adsorbent and show high adsorption capacity without any reductions of magnetic intensity and aggregation of adsorbents under five repeating cycles.