Theoretical Density Functional Theory Study Research Articles

A novel molecularly imprinted electrochemical sensor based on MnO-Fe3O4@C was designed with DFT theoretical study for the detection of thiamphenicol in food

In this study, a new molecularly imprinted electrochemical sensor is presented for thiamphenicol (TAP) based on MnO-Fe3O4@C and a molecularly imprinted polymer (MIP). In the synthesis process of MIP, the density functional theory (DFT) was applied to simulated the interaction between different functional monomers and template molecules, and screen the optimal functional monomers and the ratio of optimal template molecules to functional monomers, which guided the electrochemical in-situ polymerization of MIP. The composite materials were evaluated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and the electrochemical performance of molecular imprinted electrode was evaluated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, there is a strong linear correlation between the current response and TAP concentration in the 0.01–1 μM (R2=0.9988) and 1–40 μM (R2=0.9954) range. The lowest detection limit (S/N = 3) was 0.007 μM. Besides, the sensor has good reproducibility, stability and anti-interference ability, and has successfully detected analytes in milk and egg samples, which provides application prospects for constructing selective detection of TAP in food samples.

Experimental and theoretical quantum chemical studies of 2-(2-acetamidophenyl)-2-oxo-N-(pyridin-2-ylmethyl)acetamide and its copper(II) complex: molecular docking simulation of the designed coordinated ligand with insulin-like growth factor-1 receptor (IGF-1R)

Newly synthesized ligand 2-(2- acetamidophenyl)-2-oxo-N-(pyridin-2-ylmethyl)acetamide and its copper(II) complex were characterized by elemental analyses, FT-IR, UV–Vis., ESR, 1H-NMR, and thermal analysis along with the theoretical quantum chemical studies. Combined experimental and theoretical DFT (density functional theory) studies showed the ligand to be a tridentate ligand with three coordinate bonds. The complex was suggested to be in a distorted octahedral structure with dx2-y2 ground state. The activation energy, ΔE*; entropy ΔS*; enthalpy ΔH* and order of reaction has been derived from differential thermogravimetric (DTA) curve, using Horowitz–Metzeger method. The nujol mull electronic spectrum of the ligand and Cu(II) complex have been recorded and the difference of the excited and ground state densities has also been theoretically calculated and plotted to investigate the movement of electrons on excitation. The Cu(II) complex was evaluated for its antibacterial activity against two bacterial species, namely Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Antifungal screening was performed against two species (Condida albicans and Aspergillus flavus). The complex under investigation was found to possess notable biological activity. Molecular docking investigation predicted different types of non-covalent interactions of the synthesized ligand towards Insulin-like growth factor 1 receptor (ID: 5FXR).

Computational study of charge transfer iso-surface in first three excited states, electron-hole transition effects, chemical nature and bond order analysis investigations of chrysogine

This work presents the theoretical DFT (Density Functional Theory) studies and the biological application of chrysogine, a marine alkaloid. Energy minimisation and additional DFT evaluations were performed for vacuum and solvent media. It has been observed that solvation with polar solvents has resulted in a slight variation in the molecule’s properties. The Multiwfn software was employed to carry out various topological analyses. Among these, the charge transfer studies show that the second and third excited states are the most significant. From the reactivity analysis, the least energy gap (4.9624 eV) is obtained in water, indicating that chrysogine is most reactive in aqueous media. Theoretical UV studies show that the trends in λmax values correspond to n -->π* and n -->σ* electronic transitions within the molecule. An increase in medium polarity has demonstrated in the MEP (Molecular Electrostatic Potential) maps an increase in the potential range from −6.619 × 10−2 a.u. to 6.619 × 10−2 a.u. in the gas phase, to a sharp rise to −8.036 × 10−2 a.u. to 8.036 × 10−2 a.u. in ethanol, −8.098 × 10−2 a.u. to 8.098 × 10−2 a.u. in methanol, −8.130 × 10−2 a.u. to 8.130 × 10−2 a.u. in DMSO, and −8.127 × 10-2 a.u. to 8.127 × 10−2 a.u. in water. The most significant transition contributing to molecular stability from NBO (Natural Bond Orbital) analysis is: (O2-C9) π* → π* (C7-C8) with the energy of 258.13 kcal mol−1. The ADMET profile for the molecule was assimilated with the help of online servers. The molecule was docked against lung cancer target proteins (PDB ID: 1NTK, 3QFB) using software such as AutoDock Tools and PyMOL. The respective illustrations and data were visualised using Discovery Studio Visualizer. Good binding affinities (−5.69 kcal mol−1 for 1NTK and −6.64 kcal mol−1 for 3QFB proteins) and interactions were achieved with the selected targets.

Material Properties ofn‐Type β‐Ga2O3Epilayers with In Situ Doping Grown on Sapphire by Metalorganic Chemical Vapor Deposition

AbstractIn this study, in situ, Si‐doped heteroepitaxial Ga2O3layers are grown onc‐plane sapphire by metalorganic chemical vapor deposition. The X‐ray diffraction peaks of the doped Ga2O3epilayers shows ß‐phase of Ga2O3,and full width at half maximum of Ga2O3crystallinity is decreased at a Tetraethoxysilane (TEOS) molar flow rate of 2.23 × 10−7 mol min−1but increased with higher flow rates. The dopant concentrations of Ga2O3grown at 825 °C with TEOS molar flows of 2.23 × 10−7, 4.47 × 10−7, and 6.69 × 10−7 mol min−1are measured to be 5.5 × 1019, 1.1 × 1020, and 1.4 × 1020 atom cm−3, respectively, using secondary ion mass spectra and Hall measurements revealn‐type nature with carrier concentrations of 6.5 × 1017, 3.2 × 1018, and 3.9 × 1018atom/cm3, respectively. To increase Si dopant activation, Ga2O3growth temperature is raised to 875 °C. The result suggests a higher growth temperature can contribute to a greater probability of Si substitution on Ga lattice sites, which further reduces the resistivity of Ga2O3epilayer. Moreover, results are compared with theoretical Density Functional Theory studies.

A DFT theoretical and experimental study of the effect of indium doping within electrochemical deposited ZnO

The effect of indium doping within ZnO-NRs nanorods on FTO substrates was studied using integrated theory and experiments. The electrochemical deposited In-ZnO NRs were examined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV–vis spectrophotometer, electrochemical cell, and Photocurrent spectroscopy. The obtained electronic and optical characteristics of the developed ZnO and In-ZnO films were validated by density functional theory (DFT) calculations using the TB-mBJ and PBE-GGA approximations. XRD patterns demonstrate that all electrodeposited films were crystalline having a hexagonal wurtzite with a preferred growth orientation (002). Furthermore, the crystallite particle size and (002) diffraction peak intensity of the samples reduces with In doping, suggesting a reduction in crystallinity with increasing indium. SEM images reveal a nicely defined hexagonal shape morphology of pure and In-doped ZnO nanorods, with an approximate mean diameter of ∼100 nm. UV spectrophotometry experiments and DFT calculations showed that the inclusion of In leads to a minor reduction in the optical gap energy. Mott-Schottky analysis displays an improvement in the conductivity attributed to an enhanced electronic injection in In-ZnO the conduction band, thus enhancing the photoelectrochemical properties of the zinc oxide film.

Anti-Tuberculous Drug Copper Pyrazinamide: Synthesis, Characterization, Theoretical DFT, Bioactivity and Toxicity Studies in the Liver

Mycobacterium tuberculosis causes tuberculosis, an infectious disease. Pyrazinamide is a tuberculosis treatment. Metal–ligand–drug complexation can be used to improve the therapeutic efficacy of drugs. Copper pyrazinamide (CuPZA), a newly synthesized drug, is being considered for tuberculosis treatment. CuPZA was synthesized by soft synthetically reacting Cu (II) metal with pyrazinamide. The metal-drug complexes were characterized using elemental analysis, melting point determination, TGA analysis, FT-IR spectrometer, hot-stage microscopic study and X-ray crystallography. Copper (II) coordination with pyrazinamide was clearly demonstrated by the results of the characterization. For molecular modeling of the CuPZA novel compound, the density functional theory (DFT) method with B3LYP functional and 6-31G(d,[Formula: see text] basis set was used. Chemical reactivity parameters such as the energy gap, global hardness and softness and the electrophilicity index demonstrate that the complex is chemically reactive in aqueous medium. Pharmacokinetic parameters studied revealed that the complex is a promising drug material, with good oral bioavailability and higher activity than first-line tuberculosis medications. The enzymes alanine aminotransferase (AST) and aspartate aminotransferase (ALT) were used to assess liver damage, whereas malondialdehyde (MDA), reduced glutathione (GSH), glutathione-S-transferase (GST) and superoxide dismutase (SOD) were used to assess liver antioxidant status. ALT, AST and GSH levels were not significantly different across all test parameters, but GST activity and MDA levels were significantly higher (p 0.05) in the 20[Formula: see text]mg CuPZA group compared to the control. CuPZA’s LD50 was lower (47.962[Formula: see text]g/ml) than PZA’s (83.624[Formula: see text]g/ml). According to the findings, pyrazinamide does not cause oxidative stress and is thus safer than CuPZA. CuPZA did not reduce antioxidant levels in rats, but it did cause oxidative stress. Furthermore, oxidative stress has no effect on liver enzyme levels, which are indicators of liver damage, indicating that the animals are in the early stages of oxidative stress. Copper pyrazinamide is a promising tuberculosis inhibitor with potential activity greater than first-line tuberculosis treatments. Copper pyrazinamide, on the other hand, should be used for tuberculosis treatment for a shorter period of time than pyrazinamide.

DFT theoretical and experimental studies unraveling the structural and electronic properties of niobium doped calcium apatite ceramics

Calcium apatite ceramics consisting of a biphasic structure of hydroxyapatite (HAP) and tricalcium phosphate (β-TCP) have been widely explored by biomedical communities for hard-tissue engineering applications, especially bone replacement as it has the potential to mimic the properties of the natural bones. Doping of cations in the hydroxyapatite (NbHAP) is expected to promote the alkaline phosphatase activity and thereby generation of new bone, which, however, depends on its structural and electronic properties. In the present investigation, the variation in the structural and electronic properties of NbHAP prepared by the chemical precipitation method is determined theoretically by employing density functional theory (DFT) using the B3LYP functional method in the Gaussian 09 package program and experimentally using various characterization tools. The experimental investigation by X-ray diffraction (XRD) studies revealed notable variation in the β-TCP content in NbHAP when compared to the pristine HAP, while the Inductively Coupled Plasma spectroscopic results revealed the presence of Nb ions in doped HAP and along with the percentage increase in β-TCP content in NbHAP by Ca/P molar ratio variation, when compared with the HAP system. In addition, experimentally determined Raman spectroscopic values revealed the formation of substitution-type solid solutions in the NbHAP system. The doping of niobium ions was shown to cause noticeable variations in the reactivity indices, as indicated by a number of electronic characteristics that were calculated using DFT. Furthermore, variations in the theoretical parameters such as dipole moment, polarizability, and electric susceptibility revealed that NbHAP is better bioceramic material for hard-tissue engineering applications in comparison to HAP.

Structural modification and band gap engineering of carbon nano-onions via sulphur doping: Theoretical DFT study

Density functional theory (DFT) calculations were performed to investigate the structures and electronic properties of S-doped carbon nano-onions (S-CNOs). We report a detailed study of the stoichiometric and defective (monovacancy (MV) and divacancy (DV)) CNOs with different doping contents and distribution patterns. The results indicate the natural tendency of sulphur to occur in groups around the edges of the local deformations and at the defects that are in very good qualitative agreement with the experimental data. [22] More importantly, the five-membered rings containing disulphide bridges are the most stable binding motif in the structure of CNOs. However, the S-S motif can also be located in the six-membered ring either with both two-coordinated S atoms or with one- and three-fold coordinated S atoms. For defective systems, we also studied the energetic stability of the MV- and DV-containing S-CNOs. The results reveal that the most stable position of sulphur is the two-fold coordinated carbon site in the first case, whereas in the second case, it is the one linking octagonal and pentagonal rings. Furthermore, the electronic analysis indicates that the position and concentration of dopant and the type of defect unambiguously influence the band gap energy in both stoichiometric and defective CNOs.

Hybrid copper halide material with perovskite like structure with tetrahedral units; synthesis, characterization and optical properties

Many attempts have been made to substitute lead as the metal cation in perovskite materials but, at the same time, retain its favorable optical and electrical properties. Copper is a naturally abundant metal as well as more environmentally friendly than Pb, thus, can be used as the metal cation in regards to possible substitution candidate perovskites. Herein we report the synthesis and optoelectronic properties of two novel compounds with perovskite-like structure and Cu as the central cation. The analysis includes Powder XRD data and a Density Functional Theory (DFT) study for a thorough understanding of their structure. By Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Vibronic studies (FTIR, Raman), Nuclear Magnetic Resonance (NMR) and Mass spectra we fully explain the chemical analysis of the final material. Complete analysis of their optoelectronic properties is explained and presented with UV–vis measurements. Furthermore, we correlate their properties with their structure with Raman spectroscopy but also via computational theoretical DFT studies.

Experimental and DFT theoretical study for understanding the adsorption mechanism of toxic dye onto innovative material Fb-HAp based on fishbone powder

The massive production of liquid discharges from the textile industry represents a global challenge based primarily on maintaining the equilibrium between ecological safety and commercial gain. In this regard, the physicochemical treatment of fishbone powder leads to hydroxyapatite (Fb-HAp) which is an innovative nanocomposite with effective morphology and specific surface area for the removal of the toxic dye Brilliant Green (BG) in an aqueous solution. The maximum adsorption capacity of BG on the Fb-HAp adsorbent’s surface is 49.1 mg g−1. The kinetics and isotherm of BG dye adsorption on Fb-HAp are best represented by the pseudo-second order’s equation and Langmuir's model, while the thermodynamic parameters show that the reaction is physical, feasible, spontaneous, and endothermic. The adsorption of BG on Fb-HAp experimental values were consistent with the values predicted by the response surface methodology and lead to a maximum removal rate of 99.87% under the conditions of pH 12, adsorbent dose 1 g L−1, and dye’s concentration 10 mg L−1. Quantum chemical calculations were executed using density functional theory (DFT) calculations at B3LYP 6-31G (d,p) to correlate their electronic properties with the experimental results. Based on the high electrophilicity values, low electronegativity, and Monte Carlo results, it is found that the basic form of the BG dye has a large overlap with the Fb-HAp adsorbent compared to the acid form. The low cost of the Fb-HAp material ($1.384 per gram) and its regeneration cycles show that it is environmentally friendly and very effective for dye removal in the textile industry.

Photo- and Electroluminescent Neutral Iridium(III) Complexes Bearing Imidoylamidinate Ligands.

Imidoylamidinate-based heteroleptic bis(2-phenylbenzothiazole)iridium(III) and -rhodium(III) complexes [(bt)2M(N∩N)] (bt = 2-phenylbenzothiazole, N∩N = N'-(benzo[d]thiazol-2-yl)acetimidamidyl (Ir1 and Rh1), N'-(6-fluorobenzo[d]thiazol-2-yl)acetimidamidyl (Ir2), N'-(benzo[d]oxazol-2-yl)acetimidamidyl (Ir3), N'-(1-methyl-1H-benzo[d]imidazol-2-yl)acetimidamidyl (Ir4); yields 70-84%) were obtained by the reaction of the in situ-generated solvento-complex [(bt)2M(NCMe)2]NO3 and benzo[d]thia/oxa/N-methylimidozol-2-amines in the presence of NaOMe. Complexes Ir1-4 exhibited intense orange photoluminescence, reaching 37% at room temperature quantum yields, being immobilized in a poly(methyl methacrylate) matrix. A photophysical study of these species in a CH2Cl2 solution, neat powder, and frozen (77 K) MeOC2H4OH-EtOH glass matrix─along with density-functional theory (DFT), ab initio methods, and spin-orbit coupling time-dependent DFT calculations─verified the effects of substitution in the imidoylamidinate ligands on the excited-state properties. Electrochemical (cyclic voltammetry and differential pulse voltammetry) and theoretical DFT studies demonstrated noninnocent behavior of the imidoylamidinate ligands in Ir1-4 and Rh1 complexes due to the significant contribution coming from these ligands in the HOMO of the complexes. The iridium(III) species exhibit a ligand (L, 2-phenylbenzothiazole)-centered (3LC), metal-to-ligand (L', imidoylamidinate) charge-transfer (3ML'CT,3MLCT) character of their emission. The imidoylamidinate-based iridium(III) species were proved to be effective as the emissive dopant in an organic light-emitting diode device, fabricated in the framework of this study.

Impact of coordination ability of the selected anions on tuning the structure of Hg(II) complexes constructed from a neutral dithione ligand: Iodine uptake and DFT theoretical studies

In view to examine the role of coordination potential of the selected anions on architect of complexes, HgL2](ClO4)2 (C1) and [HgL2](PF6)2 (C2) were synthesized with a HgS4 core structure by a flexible sulfur donor (1,1-bis(3-methyl-4-imidazoline-2-thione)methane ligand(L). The C1 was crystalized via a branched tube method in MeOH/H2O as a solvent. They have been characterized by the FT-IR, elemental analysis, X-ray powder diffraction (PXRD), density functional theory (DFT) calculations, and considered for the iodine adsorption experiments. Although MOFs and CPS were extensively being studied, but mono and binuclear complexes were rarely used as an adsorbent for removal of the iodine. Additionally, to probe the impact of anions on the structure of complexes, and iodine uptake properties, C1 and C2 were compared with the published dimeric ones [Hg2L2Cl4](C3) and [Hg2L2Br4](C4) with a HgX2S2 core structure. All complexes showed a good performance in removal of iodine from the pollutants. This was supported by a sharp decrease in the intensity of a band at 523 nm nominated to the π*g(p) (HOMO) → σ*u(p) (LUMO) transitions in the free I2 molecule. The iodine capture performance of the monomeric complexes is substantially different with the dimeric ones. C1and C2 remove more than 99% of iodine molecules in the solution within 2 h, whereas C3 and C4 need 24 h to achieve the equilibrium point. The DFT studies and band gap calculations confirmed a charge transfer transition from each of the complexes to the σ*u(p) (LUMO) of the adsorbed iodine molecules with a lower energy relative to the free I2 band gap. Nonlinear optical responses (NLO) and charge transfer properties of the C1-C4 complexes were inspected by the DFT calculations.

A DFT theoretical and experimental study about tetracycline adsorption onto magnetic graphene oxide

This work reports the study of tetracycline adsorption on magnetic graphene oxide (GO·Fe3O4) from theoretical and experimental approaches. From the theoretical side, the combination of ab initio and Density Functional Theory (DFT) presents the structural and electronic properties of magnetic nanoadsorbent and tetracycline, revealing chemical adsorption between tetracycline and GO·Fe3O4. From the experimental viewpoint, the synthesis of GO·Fe3O4 was performed via co-precipitation method with control of magnetite (Fe3O4) incorporation on the GO surface. The nanoadsorbents were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The maximum tetracycline adsorption capacity was 531.93 mg g−1 using 50 mg of GO·Fe3O4 1:1, with an initial concentration of TC (1000 mg L−1), pH 7.0 at 293 K. The thermodynamic parameters showed that the process was spontaneous, exothermic, and chemical. Theoretical and experimental studies were coherent and showed that tetracycline adsorption on GO·Fe3O4 occurs by chemisorption mechanism. In summary, magnetic nanoadsorbent (GO·Fe3O4 1:1) proves to be an efficient nanomaterial for removing tetracycline from aqueous solutions, excluding subsequent process steps.

Microwave-assisted synthesis, DFT theoretical study and biological activities evaluation of two phosphonylated m-toluidine derivatives

An easy and efficient microwave-assisted method has been developed for the synthesis of two phosphonylated molecules: α-aminophosphonic acid (MTA) and α-aminophosphonate ester (MTE). To achieve these, we have synthesized the products from m-toluidine, under microwave conditions. All of the obtained compounds were characterized by Microanalysis, UV–Vis, FT-IR, and 1H, 13C and 31P NMR spectroscopic methods. The spectral results are in good line with the proposed structures. Density Functional theory (DFT) calculations were carried out using Gaussian09 program package, using 6–31G++(d,p) basis set. The frontier orbital energies were presented and have been used to predict global reactivity indices. Results showed that MTE is more reactive and less stable than MTA. The Mulliken atomic charges, dipole moment and thermodynamic proprieties were also calculated and discussed. In addition, the target compounds were evaluated for their in vitro antioxidant, antimicrobial and antienzymatic activities. The biological assays indicated that these compounds displayed potent inhibitory activity toward acetylcholinesterase (MTE: 92.71±0.91%, MTA: 67.32±0.52%) and butyrylcholinesterase (MTE: 79.16±0.47% and MTA 34.80±0.76%). It was also found that they act as excellent antiradical agents (ABTS: MTA/226.077±0.29 μg/ml, MTE/ 535,993±0.30 μg/ml and DPPH: MTA/311.853 ± 0.14 μg/ml, MTE/621.627 ± 0.12 μg/ml). In addition, these compounds exhibited the highest antibacterial and antifungal properties.

CO and H2 adsorption on Au-Ni bimetallic surfaces: a combined experimental and DFT theoretical study

Au-Ni bimetallic thin films were grown on refractory metal substrates. CO and H2 adsorption on Au-Ni bimetallic surfaces have been studied by a combination of in situ polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. It is found CO desorption peak shifts from 413 K on pure Ni surfaces to 293 K on the isolated Ni atoms formed by alloying with Au atoms. The sharp decrease of CO desorption temperature on Au-Ni surfaces with increasing Au coverage is caused by the change of the favored CO adsorption sites from bridge/hollow sites on pure Ni surfaces to Ni top sites on Au-Ni bimetallic surfaces. In situ PM-IRRAS shows two CO adsorption bands on Au sites at 2119 cm−1 and 2103 cm−1 on Au-Ni surfaces at 80 K, which are due to CO bound on under-coordinated Au atoms and electron negatively charged Au sites modified with nearby Ni atoms, respectively. Even with the Au-Ni surface temperature at as low as 100 K, CO adsorption induced Ni surface segregation has been observed by in situ PM-IRRAS. Furthermore, DFT calculation results discover the adsorption energy of CO on Ni top sites continues to decrease with increasing Au coverage due to the geometric ensemble effect and the lowered d-band center after Ni alloying with Au. H2 desorption temperature decreases from 363 K on pure Ni thin films to 302 K with increasing Au coverage to 0.6 ML. A new H2 peak appears at around 170 K on the Au-Ni surfaces with Au coverages between 0.6 ML and 0.9 ML. This new H2 TPD peak is assigned to H2 desorption from the totally isolated Ni sites. With Au coverage above 1.5 ML, there is no any H2 desorption detected. The combined surface science studies and DFT calculations provide new insights into the surface structure-activity correlation of Ni-base bimetallic surface alloys.

Novel dual-template molecular imprinted electrochemical sensor for simultaneous detection of CA and TPH based on peanut twin-like NiFe2O4/CoFe2O4/NCDs nanospheres: Fabrication, application and DFT theoretical study

Hollow peanut-shaped NiFe2O4/CoFe2O4 twinned nano-spherical shell composite materials have interconnected electron channels and excellent electrochemical performance, which prompted the use of this unique spatial structure to fabricate efficient electrochemical sensors. In this work, N-doped carbon dots (NCDs) incorporated into magnetic NiFe2O4/CoFe2O4 nanoparticle shell (NiFe2O4/CoFe2O4/NCDs) modified glassy carbon electrode (GCE) was applied to construct a dual-template molecularly imprinted polymer (MIP) based electrochemistry sensor (NiFe2O4/CoFe2O4/NCDs/MIP/GCE) for the simultaneous detection of catechin (CA) and theophylline (TPH). MIP was fabricated by an in-situ electrochemical polymerization strategy based on the theoretical exploration and density functional theory (DFT) computer directional simulation to screen out the optimal functional monomer (L-arginine) and the optimal ratio between the dual template molecules (CA and TPH) and functional monomer. The materials were characterized by SEM, TEM, XRD, XPS, and TGA. Besides, electron binding energy, binding constant, and imprinting factor were investigated. With the optimal conditions, the proposed electrochemical dual detection system showed outstanding analytical performance for the simultaneous sensing of CA and TPH, with an ultralow detection limit (LOD, S/N = 3) of 1.3 nM for CA in 0.01–1 μM (R2 = 0.9956) and 1–50 μM (R2 = 0.9928), as well as a LOD of 20.0 nM for TPH in the linear range of 0.1–100 μM (R2 = 0.9939), respectively. Also, the selectivity and anti-interference performances of the fabricated sensor were performed by differential pulse voltammetry and chronoamperometry, and successfully detected the analyte from tea drinks and human urine samples with the recovery rates ranging from 98.22% to 104.76% and relative standard deviations (RSD) were 1.19%–3.81%, demonstrated the sensor has excellent stability, repeatability, and reproducibility, which paves the way for other platforms to use this nanomaterial for the detection of antioxidant in the filed food safety.

Synthesis, X-ray crystallography characterization, and DFT theoretical studies of a new metal compound [CdCl2(4-aminopyridine)2

• The new polymeric 4-aminopyridine complex was obtained in crystal form in this study. • The FT-IR and single crystal XRD (SC-XRD) spectra of this complex were recorded. • In addition, various theoretical properties of this complex were calculated in the Gaussian 03 program and experimentally elemental and thermal analyzes were performed. • Various data obtained from this complex were also discussed. In this study, the crystal of the new [CdCl 2 (4-aminopyridine) 2 ] n metal compound based on 4-aminopyridine (4AP) and cadmium(II) chloride (CdCl 2 ) was synthesized and some of its spectroscopic and structural properties were investigated. This compound has been experimentally characterized using FT-IR spectroscopy, elemental, thermal analysis, and single crystal X-ray diffraction (SC-XRD) techniques. In addition, molecular modeling of this compound was performed using Density Functional Theory (DFT) B3LYP, LanL2Dz base sets. Some chemical properties of the metal compound were calculated from the resulting HOMO and LUMO values and natural bond orbital (NBO) analysis. General information about the structural and chemical properties of metal compound has been obtained by considering the changes in the characteristic values of 4AP and CdCl 2 molecules. According to the crystallographic data, the [CdCl 2 (4AP) 2 ] n compound has an orthorhombic crystal system and the Fdd2 space group. It has been observed that the crystal structure of the obtained compound consists of N-H∙∙∙Cl and N-H•••N hydrogen bonds between 4AP and CdCl 2 molecules. The thermal behavior of this compound was obtained by examining the temperature dependent change of its mass in nitrogen gas environment.

Synthesis, characterization, electrochemistry, DFT and kinetic study of the oligothiophene-containing complex [Rh((C4H3S-C4H2S)COCHCOCF3)(CO)(PPh3)

The synthesis, electrochemistry, oxidative addition kinetics and computational chemistry study are presented for the [Rh((C4H3S-C4H2S)COCHCOCF3)(CO)(PPh3)] complex. Through chemical and electrochemical oxidation, this rhodium triphenylphosphine complex was converted from rhodium(I) to a rhodium(III) complex. The chemical kinetics, studied by the NMR, UV/Vis and IR, of the oxidative addition of CH3I to [Rh((C4H3S-C4H2S)COCHCOCF3)(CO)(PPh3)] indicated the formation of rhodium(III) alkyl 1, rhodium(III) acyl 1 and rhodium(III) alkyl 2 isomers respectively. A theoretical density functional theory study shed light on the geometry of the different reactants, transition states and reaction products. The second order rate constant of the [Rh((C4H3S-C4H2S)COCHCOCF3)(CO)(PPh3)] + CH3I oxidative addition reaction is 0.0027 mol−1 dm3 s−1 in CHCl3 at 25 °C. A linear relationship was established between the irreversible electrochemical oxidation potential of rhodium(I), Epa(Rh) and the second order rate constant of the oxidative addition reaction for a series of 17 different [Rh(β-diketonato)(CO)(PPh3)] complexes.

Theoretical DFT Studies on Free Base, Cationic and Hydrochloride Species of Narcotic Tramadol Agent in Gas Phase and Aqueous Solution

Theoretical studies based on the density functional theory (DFT) have been performed to study structural and vibrational properties of the free base, cationic, and hydrochloride species of narcotic tramadol agent in the gas phase and aqueous solution. In both media, B3LYP/6-31G* calculations were used while in solution, the self-consistent reaction field (SCRF) method together with the integral equation formalism variant polarised continuum (IEFPCM) and universal solvation model density (SMD) models have been employed because these models consider the solvent effects. The vibrational studies have revealed that the species cationic is present in the solid phase because the most intense band predicted for the hydrochloride in infrared and Raman spectra is not observed in the experimental spectra. The harmonic force fields, together with the normal internal coordinates and scaling factors, have allowed the complete vibrational assignments of 126, 129, and 132 vibration modes expected for the free base, cationic, and hydrochloride species, respectively, by using the SQMFF methodology. The cationic species evidence the most negative solvation energy and higher hydration in solution in agreement with its lower stability, while the hydrochloride species is the most reactive in solution. MK charges and NBO and AIM studies support cationic species' instability due to the positive charge on N atom. Comparisons of the experimental UV spectrum of hydrochloride tramadol with the predicted for the three species suggest that the free base, cationic, and hydrochloride species can be present in solution. Comparisons of predicted infrared, Raman, 1H, and 13C NMR and electronic spectra for the free base, cationic, and hydrochloride species of tramadol with the corresponding experimental ones have evidenced reasonable correlations for the cationic species showing that this species present in the solid phase and in solution.

Relation between structural patterns and magnetism in small iron oxide clusters: reentrance of the magnetic moment at high oxidation ratios.

Due to quantum confinement effects, the understanding of iron oxide nanoparticles is a challenge that opens the possibility of designing nanomaterials with new capacities. In this work, we report a theoretical density functional theory study of the structural, electronic, and magnetic properties of neutral and charged iron oxide clusters FenOm0/± (n = 1-6), with m values until oxygen saturation is achieved. We determine the putative ground state configuration and low-energy structural and spin isomers. Based on the total energy differences between the obtained global minimum structure of the parent clusters and their possible fragments, we explore the fragmentation channels for cationic oxides, comparing with experiments. Our results provide fundamental insight on how the structural pattern develops upon oxidation and its connection with the magnetic couplings and net total moment. Upon addition of oxygen, electronic charge transfer from iron to oxygen is found which weakens the iron-iron bond and consequently the direct exchange coupling in Fe. The binding energy increases as the oxygen ratio increases, rising faster at low oxidation rates. When molecular oxygen adsorption starts to take place, the binding energy increases more slowly. The oxygen environment is a crucial factor related to the stabilities and to the magnetic character of iron oxides. We identified certain iron oxide clusters of special relevance in the context of magnetism due to their high stability, expected abundance and parallel magnetic couplings that cause large total magnetic moments even at high oxidation ratios.