Frontier Molecular Orbital Calculations Research Articles

Influence of tartaric acid on the electron transfer between oxyanions and lepidocrocite

Iron oxide minerals control the environmental behavior of trace elements. However, the potential effects of electron transfer directions by iron oxides between organic acids and trace elements remain unclear. This study investigates the redox capacity of tartaric acid (TA) with chromate (Cr(Ⅵ)) or arsenate (As(V)) on lepidocrocite (Lep) from the perspective of electron transfer. The results demonstrated the configurations of TA (bidentate binuclear (BB)), As(V) (BB), and Cr(Ⅵ) (BB and protonated monodentate binuclear (HMB)) on Lep. Frontier molecular orbital calculations and X-ray photoelectron spectroscopy (XPS) binding energy shifts further indicated different electron transfer directions between TA and the oxyanions on Lep. The iron of Lep might act as electron acceptors when TA is adsorbed, whereas the iron and oxygen of Lep act as electron donors when As(V) is adsorbed. The iron of Lep might accept electrons from its oxygen and subsequently transfer these electrons to Cr(Ⅵ). Macroscopic validation experiments showed the reduction of Cr(VI), whereas no reduction of As(V). The XPS analysis showed a peak shift, with the possible formation of As–Fe–TA ternary complexes and electron transfer on Lep. These findings indicate that mineral interfacial electron transfer considerably influences the transport and transformation of oxyanions.

Intermolecular interactions in 4-bromoaryl derived aldimines: X-ray structure, Hirshfeld surface analysis, DFT and molecular docking studies

A convenient and facile synthesis of (E)-N-(4-bromophenyl)-1-phenylmethanimine (b), (E)-N-(4-bromophenyl)-1-(2,4-dinitrophenyl) methanimine (c) and (E)-4-(((4-bromophenyl)imino) methyl)-2-methoxyphenol (d) was accomplished by refluxing 4-bromo aniline(a) with an appropriate aldehyde in solvent methanol. X-ray crystallography, theoretical computations, and spectroscopic techniques were utilized to describe and detect interactions between and among various groups of synthesized imines (b-d). Compound b-d crystallize in monoclinic crystal systems with space groups Pnma, P21, P21/c, and P21/c, respectively, whereas compound a crystallize in orthorhombic crystal systems. To identify the intermolecular interactions, Hirshfeld surface analysis was also used, emphasizing the importance of hydrogen bonding, van der Waals forces, and the impact of substituents. Hirshfeld surface fingerprint plots were used to study crystal packing motifs. Energy frameworks examined the electrostatic energy input that stabilizes solid state structures. Additionally, studies pertaining to the optimization of the structure, frontier molecular orbital (highest occupied–lowest unoccupied) and molecular electrostatic potential calculations were conducted. Lastly, using the membrane protein of the naturally occurring fungus Candida albicans SC5314, molecular docking investigations of compounds a–d were conducted (PDB-ID 7RJE)

DFT study on the effects of substituents on the structure and properties of dithiophosphate collectors

AbstractThe structures and properties of seven substituted dithiophosphate (DTP) collectors containing three types of functional groups (O2PS2, C2PS2, and N2PS2) were studied using density functional theory. The collectors studied were dibutyl dithiophosphate (DNBDTP), diisobutyl dithiophosphate (DIBDTP), dibutoxyethyl dithiophosphate (DBOEDTP), xylenol dithiophosphate (DMPDTP), diisobutyl dithiohypophosphite (3418A), diphenylamine dithiophosphate (DTADTP), and dicyclohexylamine dithiophosphate (DCADTP). The structural analysis showed that the PS bond lengths in the C2PS2 and N2PS2 types are longer than those in the O2PS2 type, indicating that the strength of the PS bond is weaker in the former two. The frontier molecular orbital studies showed that the energy differences between the highest occupied molecular orbitals (HOMO) of 3418A (C2PS2 type) and DCADTP (N2PS2 type) and the lowest unoccupied molecular orbital (LUMO) of galena are significantly lower than those of the other collectors, suggesting that C2PS2 type and N2PS2 type with cyclohexane could enhance the interaction with galena. Using the Fukui function to calculate the nucleophilicity and electrophilicity of the sulfur atom indicated that the S atom exhibits nucleophilicity, especially in DMPDTP and DTADTP, which contain benzene rings, and the S atom exhibits strong nucleophilicity without electrophilicity. However, due to the lack of contribution from S atoms to the LUMO orbitals, the S atoms in these two compounds are not participate in any LUMO reactions. The adsorption results demonstrated that 3418A (C2PS2 type) and DCADTP (N2PS2 type) exhibit the strongest adsorption on Pb2+ ions, while DMPDTP (C2PS2 type) and DTADTP (O2PS2 type) which contain benzene rings, as well as DBOEDTP (C2PS2 type) which does not contain a benzene ring, exhibit weaker interaction compared to the other compounds. These are consistent with the results of the frontier molecular orbital and electrophilic nucleophilicity calculations.

XRD/DFT, Hirshfeld surface analysis and molecular modelling simulations for unfolding reactivity of newly synthesized vanillin derivatives: excellent optical, NLO and protein binding efficiency

New vanillin derivatives, namely, ethyl (4-formyl-2-methoxyphenoxy)acetate (2a) and 2-(4-formyl-2-methoxyphenoxy)-N-phenylacetamide (2b), respectively, were synthesized and characterized by NMR (1H and 13C), IR, mass spectra and confirmed by single-crystal X-ray analysis. Hirshfeld surface (HS) analysis was performed to probe intra- and intermolecular interactions and surface reactivity. 2D fingerprint plots (FP) were used to study the nature and percentage contribution of intermolecular interactions leading to the formation of the crystal unit. Density functional theory (DFT) simulations were used to obtain the electronic structure and reactivity of the new molecules. Natural population analysis (NPA) and frontier molecular orbital (FMO) calculations reveal significant charge transfer and a reduced HOMO-LUMO gap up to 4.34 eV for 2b. Bader’s quantum theory of atoms in molecules (QTAIM) study is utilized to understand the surface topological and bonding nature of 2a and 2b. The performed molecular electrostatic potential (MESP) and density of states (DOS) study further suggest sites likely to be attractive to incoming reagents. At the same time, hyperpolarizability (βo) is used to characterize the nonlinear optical properties, and TD-DFT study shows the excitation energy and absorption behavior. In silico studies were performed, including docking, binding free energies (MMBGSA) and molecular dynamics simulations. Compounds 2a and 2b were docked with RdRp of SARS-Cov-2, and the MMBGSA for 2a and 2b were −30.70 and −28.47 kcal/mol, respectively, while MD simulation showed the stability of protein-ligand complexes. Communicated by Ramaswamy H. Sarma

Synthesis of Hybrid Porphyrin(2.1.2.1)s and Their Complexation.

Novel hybrid porphyrin(2.1.2.1)s and their boron and copper complexes were synthesized using the "toy bricks" synthetic method. Crystal data, frontier molecular orbital calculations, and electrostatic potential surface maps reveal that hybridization in the porphyrin(2.1.2.1) donor-acceptor unit controls the selective coordination of BF2.

Quantum Chemical and Biological Properties of Coumarin Derivative Compound

This work presents the characterization of 8-t-buthyl-4-methyl-2H- chromen 2-one by quantum chemical calculations and spectral techniques. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C NMR chemical shift values of title compound in the ground state have been calculated using the density functional method (B3LYP) with the 6-31G(d) basis set. The theoretical vibrational frequencies and chemical shift values show good agreement with experimental values. In addition, DFT calculations of molecular electrostatic potentials and frontier molecular orbitals of the title were carried out at the B3LYP/6-31G(d) level of theory. The title compound was screened for antibacterial, antifungal and antioxidant activities.

Theoretical and experimental study of 5-ethoxymethylfurfural and ethyl levulinate production from cellulose

Theoretical simulations and experiments were taken to explore the mechanism of cellulose conversion into 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) catalyzed by a mixed acid of Lewis acid and Brønsted acid. Up to 64.8 % total yield of EMF and EL can be obtained when the ratios of Lewis/Brønsted acid and water/ethanol (v/v) were 1:2 and 3:7 respectively. The results showed that Lewis acid and water could reduce the activation energy of EMF formation from 75.6 to 47.9 kJ mol−1, and mixed acids and water/ethanol system were beneficial to the accumulation of EMF. Moreover, the results of molecular dynamics (MD) simulation indicated that Lewis acid could promote the distribution of Bronsted acid around the β-1,4 glycosidic bond of cellobiose. The combination of DFT and frontier molecular orbital (FMO) calculation demonstrated that the breakage of the β-1,4 glycosidic bond was the main rate-limiting step of cellulose hydrolysis. Meanwhile, the mixed acid and water/ethanol system could accelerate the hydrolysis due to the reducing energy barrier and HOMO-LUMO gap. This study gave a deep insight into the mechanism of Lewis acid with Brønsted acid on cellulose conversion into EMF and EL.

Unraveling the molecular structure, spectroscopic properties, and antioxidant activities of new 2,4-dinitrophenylhydrazone derivatives through a comprehensive investigation

The synthesis and characterization of novel 2,4-dinitrophenylhydrazone (2,4-DNPH) derivatives were investigated using a comprehensive combination of experimental and theoretical approaches. Spectroscopic techniques such as 1H NMR, IR, Raman, and UV–Vis were employed to probe the structural and chemical properties of the synthesized compounds. These compounds were tested for their in vitro anti-oxidant activity. All the synthesized derivatives showed good to excellent activities. Density functional theory (DFT) calculations at the B3LYP functional with 6-31G and 6–311++G(d,p) basis sets were performed to reveal the molecular nature of the synthesized derivatives. Conformational analysis confirmed the stability of the optimized structures. The DFT simulations revealed the presence of hydrogen bonding between the N–H and nitro groups and further explored the charge transfer within the molecule as well as the sites that are favorable for electrophilic and nucleophilic attacks. The frontier molecular orbital (FMO) calculations provided insights into various reactivity parameters, such as ionization potential, electron affinity, electronegativity, chemical hardness, and chemical softness. Overall, this study provides a deeper understanding of the molecular structure, spectroscopic properties, and reactivity of these new 2,4-dinitrophenylhydrazone derivatives, which could have potential applications in the field of biochemistry.

Assessment of the hypoglycemic and anti-hemostasis effects of Paederia foetida (L.) in controlling diabetes and thrombophilia combining in vivo and computational analysis

Paederia foetida is valued for its folk medicinal properties. This research aimed to assess the acute toxicity, hypoglycemic and anti-hemostasis properties of the methanolic extract of P. foetida leaves (PFLE). Acute toxicity of PFLE was performed on a mice model. Hypoglycemic and anti-hemostasis properties of PFLE were investigated on normal and streptozotocin-induced mice models. Deep learning, molecular docking, density functional theory, and molecular simulation techniques were employed to understand the underlying mechanisms through in silico study. Oral administration of PFLE at a dosage of 300 µg/kg body weight (BW) showed no signs of toxicity. Treatment with PFLE (300 µg/kg/BW) for 14 days resulted in a hypoglycemic condition and a 30.47% increase in body weight. Additionally, PFLE mixed with blood exhibited a 44.6% anti-hemostasis effect. Deep learning predicted the inhibitory concentration (pIC50, nM) of Cleomiscosins against SGLT2 and FXa to be 7.478 and 6.017, respectively. Molecular docking analysis revealed strong binding interactions of Cleomiscosins with crucial residues of the target proteins, exhibiting binding energies of −8.2 kcal/mol and −7.1 kcal/mol, respectively. ADME/Tox predictions indicated favorable pharmacokinetic properties of Cleomiscosins, and DFT calculations of frontier molecular orbitals analyzed the stability and reactivity of these compounds. Molecular simulation dynamics, principal component analysis and MM-PBSA calculation demonstrated the stable, compact, and rigid nature of the protein-ligand complexes. The methanolic PFLE exhibited significant hypoglycemic and anti-hemostasis properties. Cleomiscosin may have inhibitory properties for the development of novel drugs to manage diabetes and thrombophilia in the near future.

Controllable synthesis of 3D superhydrophilic Cd(II) ion-imprinted polymer microspheres based on OV-POSS and bifunctional monomers synergy with superior selectivity for Cd(II) adsorption

Novel 3D porous Cd(II) ion-imprinted polymer (Cd(II)-IIP) microspheres based on octavinyl polyhedral oligomeric silsesquioxane (OV-POSS) were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization technique combined with the synergistic effect of N-hydroxymethylacrylamide (NMA) and 1-vinylimidazole (1-VI) as bifunctional monomers. RAFT polymerization could achieve a controllable synthesis of polymer networks on OV-POSS. The structure, composition and properties of Cd(II)-IIP were systematically investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscope, water contact angle and thermogravimetric analysis. The results showed that the adsorbent, with a water contact angle of 0 ° and superhydrophilicity, has a high potential for application in aqueous phase systems. Different parameters influencing the sorption performance of Cd(II)-IIP, such as OV-POSS ratio, functional monomers ratio, adsorbent dosage, pH and adsorption time were optimized. Under optimal conditions, the maximum adsorption amount of Cd(II)-IIP for Cd(II) was 80.21 mg/g, and the adsorption equilibrium state could be reached within 40 min. The sorption kinetics proved that the sorption was chemisorption and the rate-limiting step was intraparticle diffusion. Thermodynamic studies showed that Cd(II) sorption was a spontaneous endothermic process. Importantly, XPS analysis, density functional theory (DFT) and frontier molecular orbital (FMO) theory calculations showed that the sorption of Cd(II)-IIP was attributed to the coordination of O and N atoms with Cd(II) on NMA and1-VI, respectively. Actual water sample analysis results indicated that Cd(II)-IIP was an adsorbent of great application potential.

Revaluation of copper(II)-Schiff base complex for sensing of d-penicillamine and development of a molecular logic gate: A combined approach

d-penicillamine (D-PA) being a tri-functional organic compound (thiol, amine, and carboxylic acid) is used as a chelating drug for many serious diseases like Wilson’s disease. Due to its serious adverse effects, regular monitoring of blood and urine for D-PA is required during the clinical application of the drug. The dye-containing Cu(II)-Schiff base complex is revisited for easy monitoring of D-PA and the development of a new molecular logic gate through extensive studies. Revaluation is carried out in light of extensive experimental evidence and theoretical rationalization which help to achieve the target. The synthesized Cu(II)-salicylaldehyde rhodamine B hydrazone complex is characterized through FTIR, NMR, Mass spectrometry, UV–Vis, and fluorescence titrations. The crystal structure of the complex is optimized through DFT studies and found distorted square planar. Calculations of Frontier Molecular Orbitals (FMOs) assist to understand the electronic and optical properties of the complex. The recognition of D-PA (LOD = 2.60 × 10-8 M) is executed both colorimetrically and fluorometrically through the “Turn-off” mechanism. The NAND-type molecular logic gate has been developed.

Density Functional Theory (DFT) Study of Methyl 2-methoxycyclohex-3-ene-1-carboxylate for structure optimization, transition state, vibrational, electronic and PES scan

The current investigation is carried out to study stability of Diels-Alder adduct methyl 2-methoxycyclohex-3-ene-1 where (a) and (e) represent axial and equatorial orientation of group .The region-selective mechanism of Diels-Alder reaction between 1-methoxy 1,3butadiene (1) and methyl acrylate (2) to give methyl 2-methoxycyclohex-3-ene-1-carboxylate (3) is studied using Density Functional Theory (DFT). There are three possible stereo-chemical products possible for this reaction such as axial-axial (a,a), equatorial-equatorial (e,e) and axial-equatorial (a,e). Density Functional Theory was carried out to study the optimized molecular structure and the Potential Energy Surface (PES) Scan. The Frontier Molecular Orbital (FMO) energy calculations were carried out and HOMO LUMO energy gap was calculated to analyse the stability and reactivity. The Molecular Electrostatic Potential (MEP) study was carried out to analyse the surface of the molecule. FTIR spectra show the vibrational analysis of molecule.

N'-(3,4-dimethoxybenzylidene)-4-methylbenzenesulfonohydrazide derivatives: Synthesis, quantum chemical method, in silico ADMET, molecular docking and molecular dynamic simulations

A new N'-(3,4-dimethoxybenzylidene)-4-methylbenzenesulfonohydrazide derivatives were prepared from a condensation reaction between 4-methylbenzenesulfonohydrazide and 3,4-dimethoxybenzaldehyde. The structure of DMSH was elucidated using various spectral techniques including FT-IR, 1HNMR and 13CNMR. The structure of DMSH bond parameters also confirmed by single crystal XRD analysis of related derivatives and optimized bond parameters are calculated by density functional theory (DFT) method at B3LYP/6–311 G (d, p) level of theory. The optimized geometrical parameters obtained by DFT calculation are in good agreement with single crystal XRD data. The experimentally observed FT-IR bands were assigned to different normal modes of the molecule. The results show a good agreement with each other when these computed bond parameters are compared to XRD values of related compounds. The stability, chemical reactivity and charge transfer within the molecule was explained by frontier molecular orbital calculations. Atomic charges on the various atoms of DMSH obtained by Mulliken population analysis. Potential reactive sites of the DMSH compound have been identified by MEP which is mapped to the electron density surfaces. The reported molecule is used as a potential NLO material since it has a high μβ0 value. The theoretical UV–vis spectrum of the compound is used to study the visible absorption maxima (λ max). The molecular docking mechanism between DMSH ligand and COVID-19/6WCF and COVID-19/6Y84 receptors were studied to investigate the binding modes of this compound at the active sites. Molecular docking outcomes have shown that the DMSH molecule can be considered as a potential agent against COVID-19/6WCF-6Y84 receptors. In addition, the theoretical parameters of the bioactive molecules were calculated to establish their drug-likeness qualities and ADME/T analysis was carried out to examine the drug properties of the synthesized compound. Molecular dynamics simulation was performed for COVID-19 main protease (Mpro: 6WCF/6Y84) to understand the elements governing the inhibitory effect and the stability of interaction under dynamic conditions. The resultant complex structures were subjected to 100 ns simulation run to estimate their binding stabilities using GROMACS. The molecular dynamics simulation studies provided essential evidence that the systems were stable during the progression of 100 ns simulation run.

MOF-derived bimetallic coordination polymer@cobalt-aluminum layered double hydroxide for highly selective CO2 adsorption: Experiments, mechanisms

Selective capture of CO2 is one of the most effective strategies for combating the greenhouse effect. In this study, we report the synthesis of a novel adsorbent—an amine-based cobalt-aluminum layered hydroxide with a hafnium/titanium metal coordination polymer (denoted as Co-Al-LDH@Hf/Ti-MCP-AS)—through the derivatization of metal–organic frameworks (MOFs) for selective CO2 adsorption and separation. Co-Al-LDH@Hf/Ti-MCP-AS achieved the maximum CO2 adsorption capacity of 2.57 mmol g−1 at 25 °C and 0.1 MPa. The adsorption behavior followed the pseudo-second-order kinetics and Freundlich isotherm models, indicating that chemisorption occurs on a non-homogeneous surface. Co-Al-LDH@Hf/Ti-MCP-AS also exhibited selective CO2 adsorption in CO2/N2 and excellent stability over six adsorption–desorption cycles. An in-depth analysis of the adsorption mechanism through X-ray photoelectron spectroscopy and density-functional theory and frontier molecular orbital calculations revealed that adsorption occurs through acid–base interactions between amine functional groups and CO2 and that the tertiary amines (N3) have the highest affinity toward CO2. Our study provides a novel strategy for designing high-performance adsorbents for CO2 adsorption and separation.

Synthesis of water-soluble novel bioactive pyridine-based azo coumarin derivative and competitive cytotoxicity, DNA binding, BSA binding study, and in silico analysis with coumarin

The diazo coupliling reaction of 3- amino pyridine with coumarin in water medium produces water soluble 6-[3-pyridyl]azocoumarin. The synthesised compound has been fully charecterised by IR, NMR, and Mass spectroscopy. The frontier molecular orbital calculations reveal that 6-[3-pyridyl]azocoumarin is more biologically and chemically active in comparison to coumarin. The cytotoxicity evaluation confirms that 6-[3-pyridyl]azocoumarin is more active than coumarin against human brain glioblastoma cell lines, LN-229 with IC50 value 9.09 μM (IC50 value for coumarin is 9.9 μM). The compound (I) has been synthesized by coupling of diazotized solution of 3-aminopyridine with coumarin in an aqueous medium at ∼ pH 10. The structure of the compound (I) has been characterized using UV–vis, IR, NMR, and Mass spectral studies. Frontier molecular orbital calculations reveal that 6-[3-pyridyl]azocoumarin (I) is more active chemically and biologically in comparison to coumarin. IC50 value 9.09 and 9.9 μM of 6-[3-pyridyl]azocoumarin and coumarin respectively obtained in cytotoxicity evaluation confirms the enhanced activity of the synthesized compound against human brain glioblastoma cell lines, LN-229. The synthesized compound also shows strong binding interactions with DNA and BSA in comparison with coumarin. The DNA binding study shows groove binding interaction of the synthesized compound with CT-DNA. The nature of interaction, binding parameters and structural variations of BSA in the presence of the synthesized compound and coumarin have been evaluated using several usefull spectroscopy approaches such as UV –Vis, time resolved and stady state flurescence. The molecular docking interaction has been carried out to justify the experimental binding interaction with DNA and BSA.

Aminosilane-functionalized Ti-based metal–organic framework for efficient and selective CO2 adsorption

Carbon dioxide capture and storage (CCS) is considered as a promising strategy for reducing CO2 emissions. However, the further development of CO2 adsorption materials with high selectivity and high adsorption capacity is the top priority of this technology. In this study, we used the μ-OH sites of the MIL-125 metal–organic framework (MOF) to modify it with aminosilane to synthesize a new MOF adsorbent (SAP-MIL-125) with improved CO2 adsorption capacity at room temperature. Although there are no open metal sites on the MIL-125 surface, it is possible to load aminosilanes onto it. Under the same adsorption conditions, the CO2 adsorption by SAP-MIL-125 was significantly improved compared to that of the original MIL-125. Adsorption isotherm and kinetics models were used to clarify that the adsorption mechanism of CO2 on SAP-MIL-125 was non-homogeneous layer chemisorption. SAP-MIL-125 has excellent selectivity toward CO2 (compared to N2) and good stability over five adsorption–desorption cycles. The adsorption of CO2 by SAP-MIL-125 is a spontaneous exothermic process. An in-depth investigation of the adsorption mechanism suggests that the acid–base interactions of carbamates is the mechanism of CO2 adsorption. Density functional theory and frontier molecular orbital calculations showed that the main adsorption sites for the modified adsorbent were nitrogen-containing groups on the surface of aminosilanes, with the primary amines having the highest affinity for CO2. In conclusion, a novel material modification method for MOFs is provided, which was used to fabricate a CO2 adsorbent with great potential for development.

Revealing specific transformation pattern of sulfonamides during wastewater biological treatment processes by molecular networking nontarget screening

Biotransformation of emerging contaminants (ECs) is of importance in various natural and engineered systems to eliminate the adverse effects of ECs toward organisms. In wastewater, structurally similar ECs may transform through similar reactions triggered by common enzymes. However, the transformation pattern for them was scarcely studied. To fill the research gaps, five sulfonamides were chosen as the targeted ECs with similar structure to explore the transformation pattern in wastewater biological treatment experiments at lab scale. Through molecular networking based nontarget screening, 45 transformation products (TPs) of sulfonamides were identified and 14 of them were newly found. On the basis, five specific transformation patterns were summarized for sulfonamides by transformation pathways comparing, reaction frequency analyzing and dominant TPs comparing. Results suggested that pterin-chelation and formylation (dominant transformation pathway) and acetylation, methylation and deamination reactions were commonly occurred for sulfonamides in wastewater. Among them, the role of formylation as the dominant transformation pathway for sulfonamides transformed in wastewater was firstly reported in present study. Subsequent frontier molecular orbital calculation suggested the active site of amino (N1H2-) may contribute the specific transformation pattern of sulfonamides. Present study reveals the specific transformation pattern of sulfonamides from the aspect of TPs and transformation pathways. In the future, knowledge on the specific transformation pattern can be used to regulate and enhance the removal of a class of ECs with similar structure rather than just one of ECs.

Adsorption of amphetamine on deep eutectic solvents functionalized graphene oxide/metal-organic framework nanocomposite: Elucidation of hydrogen bonding and DFT studies

The efficient and selective removal of amphetamine (AMP) from water bodies is significant for environmental remediation. In this study, a novel strategy for screening deep eutectic solvent (DES) functional monomers was proposed based on density functional theory (DFT) calculations. Using magnetic GO/ZIF-67 (ZMG) as substrates, three DES-functionalized adsorbents (ZMG-BA, ZMG-FA, and ZMG-PA) were successfully synthesized. The isothermal results showed that the DES-functionalized materials introduced more adsorption sites and mainly contributed to the formation of hydrogen bonds. The order of the maximum adsorption capacity (Qm) was as follows: ZMG-BA (732.110 μg⋅g−1) > ZMG-FA (636.518 μg⋅g−1) > ZMG-PA (564.618 μg⋅g−1) > ZMG (489.913 μg⋅g−1). The adsorption rate of AMP on ZMG-BA was the highest (98.1%) at pH 11, which could be explained by the less protonation of –NH2 from AMP being more favorable for forming hydrogen bonds with the –COOH of ZMG-BA. The strongest affinity of the –COOH of ZMG-BA for AMP was reflected in the most hydrogen bonds and the shortest bond length. The hydrogen bonding adsorption mechanism was fully explained by experimental characterization (FT-IR, XPS) and DFT calculations. Frontier Molecular Orbital (FMO) calculations showed that ZMG-BA had the lowest HOMO-LUMO energy gap (Egap), the highest chemical activity and the best adsorption capability. The experimental results agreed with the results of theoretical calculations, proving the validity of the functional monomer screening method. This research offered fresh suggestions for the functionalized modification of carbon nanomaterials to achieve effective and selective adsorption for psychoactive substances.

Kinetics and mechanism studies of efficient degradation of 1-hexyl-3-methylimidazolium by zero-valent iron activated persulfate

In recent years, ionic liquids (ILs) have captured much attention of environment researchers due to their widespread use and potential biotoxicity. In this work, Fe0 activated persulfate (Fe0/PS) oxidation system was systematically examined for its performance to degrade 1-hexyl-3-methylimidazolium (HMIm), a typical imidazole-based ILs, with the study of degradation kinetics, pathways, mechanisms and ecotoxicity. Under the conditions of pH 3.0, Fe0/PS/HMIm molar ratio of 200:50:1, the removal efficiency of HMIm reached 93.5 % within 10 min. With the increased of the cycle index, the degradation performance became better. The degradation of HMIm was inhibited to some extent in real waters, where the presence of inorganic ions may competitively consume or suppress the production of active species. As evidenced by the results of EPR technology and quenching experiments, •OH, SO4•−, 1O2, and O2•− were generated and involved in the degradation of HMIm, with the corresponding contribution of 9.4 %, 71.4 %, 14.0 %, and 28.7 %, respectively. Twenty-seven oxidation products were identified by HPLC-QTOF-MS analysis, and side chain breakage, hydroxylation, 1O2 initiated oxidation and sulfate addition were the main reactions leading to the four primary products. Based on the frontier molecular orbital calculation, the imidazole ring of HMIm was determined as the main active sites for free radical attack. According to ECOSAR assessment, the products in the four oxidation pathways showed a decreased toxicity than HMIm. This study demonstrates that Fe0/PS is an effective and environmentally friendly method to eliminate HMIm, which also provide some technical reference for the treatment of ILs polluted waters.

New Schiff base ligand and some of its coordination compounds: Synthesis, spectral, molecular modeling and biological studies

Schiff bases are important compounds due to their various applications, especially from the biological point of view. A series of metal complexes derived from the 2-((4-oxopentan-2-ylidene)amino)benzoic acid (H2L) with Co(II), Zn(II), Cu(II) and Ni(II) were isolated and characterized. The elemental, mass and thermal analyses confirmed the suggested 1:1 (M:L) stoichiometric. The IR and 1H NMR spectra indicated that the new Schiff's base ligand coordinated to the metal ion as binegative tridentate chelator through azomethine nitrogen along with the deprotonated carboxylate and enolized carbonyl oxygen atoms. The DFT calculations of frontier molecular orbitals for the synthesized compounds were carried out and their HOMO-LUMO energy gap (ΔEH-L) displayed good agreement with the experimentally determined optical band gap (Eg). Furthermore, the antimicrobic activity of the isolated compounds against four microorganism, Staphylococcus aureus, Vibrio cholerae, Aspergillus Niger and Aspergillus flavus were screened and indicated that the Ni(II) and Zn(II) complexes were the most active.