The gas phase hydrogen‐bonded dimers of HOCl: A high‐level quantum chemical study

The O···H? O and Cl···H? O hydrogen bonding interactions were analyzed for HOCl dimers by using B3LYP, MP2, CCSD, and MP4(SDTQ) methods in conjunction with the various basis sets. Five isomers were found for the HOCl dimer. The ZPE and BSSE corrected binding energies were computed at the different levels of theory. At the optimized geometries obtained at CCSD/AUG‐cc‐pVDZ level, energies were re‐evaluated at MP4(SDTQ)/AUG‐cc‐pVTZ and CCSD(T)/cc‐pVTZ levels of theory. We found an average of ?20.9 and ?9.6 kJ/mol for the strength of the O···H and Cl···H hydrogen bonding interactions, respectively. Excitation and vertical ionization energies as well as rotational constants were computed at different levels of theory. The quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis were used to elucidate the nature of the interactions of HOCl dimers. The interaction energies were decomposed by Morokuma methodology. We have computed Δ_fH°(HOCl) and Δ_fH°(HOCl⁺) using the atomization reactions. The Δ_fH°₂₉₈(HOCl) values are ?17.85 and ?18.05 kcal/mol by using CBS‐Q and CBS‐QB3 extrapolation models, respectively, in good agreement with the results given in JANAF tables. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Three-dimensional Brownian diffusion of rod-like macromolecules in the presence of randomly distributed spherical obstacles: molecular dynamics simulation

Brownian diffusion of rod-like polymers in the presence of randomly distributed spherical obstacles is studied using molecular dynamics simulations. It is observed that dependence of the reduced diffusion coefficient of these macromolecules on the available volume fraction can be described reasonably by a power law function. Despite the case of obstructed diffusion of flexible polymers in which reduced diffusion coefficient has a weak dependence on the polymer length, this dependence is noticeably strong in the case of rod-like polymers. Diffusion of these macromolecules in the presence of obstacles is observed that is anomalous at short time scales and normal at long times. Duration time of the anomalous diffusion regime is found that increases very rapidly with increasing both the polymer length and the obstructed volume fraction. Dynamics of diffusion of these polymers is observed that crosses over from Rouse to reptation type with increasing the density of obstacles.     

Solubility and diffusion of CO2 and H2S in the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate

The solubility and diffusion coefficient were determined for carbon dioxide and hydrogen sulfide gases in the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO₄]) at temperatures ranging from (303.15 to 353.15) K and pressures up to 1.6 MPa. The Krichevsky–Kasarnovsky equation was used to correlate solubility data and Henry’s law constants at different temperatures were obtained. The partial molar thermodynamic functions of solution such as Gibbs free energy, enthalpy, and entropy were calculated using the solubility data. A semi-infinite volume approach is used to obtain the diffusion coefficients for CO₂ and H₂S and a correlation equation with temperature is presented for each gas. Comparison showed that H₂S is more soluble than CO₂ and its diffusion coefficient is about two orders of magnitude as that of CO₂ in the ionic liquid studied in this work.     

Voltammetric investigation and amperometric detection of the bisphosphonate drug sodium alendronate using a copper nanoparticles-modified electrode

The electrochemical behavior of sodium alendronate on copper microparticle- and copper nanoparticle-modified carbon paste electrodes was investigated. In the voltammograms recorded using microparticles, a single anodic oxidation peak appeared, while using nanoparticles, two anodic peaks appeared. The anodic currents were related to the electrocatalytic oxidation of alendronate via the active species of Cu(III). The catalytic rate constant for the electrocatalytic oxidation process and the diffusion coefficient of alendronate were obtained to be 1.57 × 10³ cm³ mol⁻¹ s⁻¹ and 2.44 × 10⁻⁶ cm² s⁻¹, respectively. A sensitive and time-saving detection procedure was developed for the analysis of alendronate, and the corresponding analytical parameters were reported. Alendronate was determined with a limit of detection of 11.26 μmol L⁻¹ with a linear range of 50–6,330 μmol L⁻¹. The proposed amperometric method was applied to the analysis of commercial pharmaceutical tablets, and the results were in good agreement with the declared values.     

Extraction of crocin from saffron (Crocus sativus) using molecularly imprinted polymer solid‐phase extraction

A new molecularly imprinted polymer for extraction of crocin from saffron stigmas was prepared using gentiobiose (a glycoside moiety in crocin structure) as a template. Crocin binding to gentiobiose imprinted polymer (Gent‐MIP) was studied in comparison with a blank nonimprinted polymer in aqueous media. Affinity of the Gent‐MIP for the crocin was more than the nonimprinted polymer at all concentrations. In Scatchard analysis, the number of binding sites in each gram of polymer (maximum binding sites) and dissociation constant of crocin to binding sites were 18.4 μmol/g polymer and 11.2 μM, respectively. The Gent‐MIP was then used as the sorbent in an SPE method for isolation and purification of crocin from methanolic extract of saffron stigmas. The recovery of crocin, safranal and picrocrocin was determined in washing and elution steps. The Gent‐MIP had significantly higher affinity for crocin than other compounds and enabled selective extraction of crocin with a high recovery (84%) from a complex mixture. The results demonstrated the possibility of using a part of a big molecule in preparing a molecularly imprinted polymer with a good selectivity for the main structure.     

Unique and multiple PHAM series solutions of a class of nonlinear reactive transport model

The purpose of this paper is to visit a class of nonlinear reactive transport model in the case including advective and diffusive transport with the Michaelis-Menten reaction term. We apply the method so-called predictor homotopy analysis method (PHAM) which has been recently proposed to predict multiplicity of solutions of nonlinear BVPs. Consequently two consequential matters are indicated which confirms the authority of PHAM to identify multiple solutions: (i) The Talylor series solutions are improved by the so-called convergence-controller parameter (ii) The possibility of existence of multiple solutions is discovered in some cases for the model.     

Composition of essential oil and biological activity of extracts of Viola odorata L. from central Iran

Essential oil composition of the leaves of Viola odorata L. growing wild in Kashan, central Iran, was extracted by hydro distillation-solvent extraction method and analysed using GC-MS technique. The analysis revealed the presence of 25 identified compounds, representing 92.77% of the oil with butyl-2-ethylhexylphthalate (30.10%) and 5,6,7,7a-tetrahydro-4,4,7a-trimethyl-2(4H)-benzofuranone (12.03%) being the two main components. Several components were identified for the first time in this chemotype of V. odorata. Antioxidant and antibacterial activities of the oil, methanol and chloroform extracts were also evaluated for the first time in this research work.     

Characterization of a hierarchical network of hyaluronic acid/gelatin composite for use as a smart injectable biomaterial

Hybrid HA/Ge hydrogel particles are embedded in a secondary HA network to improve their structural integrity. The internal microstructure of the particles is imaged through TEM. CSLM is used to identify the location of the Ge molecules in the microgels. Through indentation tests, the Young's modulus of the individual particles is found to be 22 ± 2.5 kPa. The overall shear modulus of the composite is 75 ± 15 Pa at 1 Hz. The mechanical properties of the substrate are found to be viable for cell adhesion. The particles' diameter at pH = 8 is twice that at pH = 5. The pH sensitivity is found to be appropriate for smart drug delivery. Based on their mechanical and structural properties, HA-Ge hierarchical materials may be well suited for use as injectable biomaterials for tissue reconstruction.     

Synthesis, X-ray structure, electrochemistry, and theoretical studies of palladium(II) complex with a tetradentate bis(quinoline-2-carboxamide) ligand

The title complex [Pd(Me₂bqb)] (1), [Me₂bqb^2?C?=?1,2-bis(quinoline-2-carboxamide)-4,5-dimethyl-benzene dianion], has been synthesized and characterized by elemental analyses and spectroscopic methods, and the crystal and molecular structure of [Pd(Me₂bqb)] has been determined by X-ray crystallography. The complex exhibits distorted square-planar PdN4 coordination geometry with two short and two long Pd?CN bonds (Pd?CN ~1.957 and ~2.095 ?, respectively). In addition to the molecular geometry from X-ray experiment, theoretical studies have been carried out on the structure of the complex at the density functional theory (DFT-B3LYP) level in conjunction with effective core potential basis set (LANL2DZ) for Pd atom and 6-311++G(d,p) basis set for N, O, C and H atoms. Electrochemical studies in CH₂Cl₂ solution revealed A reversible redox process corresponding to the Pd^II/Pd^III couple with E _1/2 at 0.924?V (vs. SCE).     

Semi-empirical study of ortho-cresol photo degradation in manganese-doped zinc oxide nanoparticles suspensions

ABSTRACT: The optimization processes of photo degradation are complicated and expensive when it is performed with traditional methods such as one variable at a time. In this research, the condition of ortho-cresol (o-cresol) photo degradation was optimized by using a semi empirical method. First of all, the experiments were designed with four effective factors including irradiation time, pH, photo catalyst's amount, o-cresol concentration and photo degradation % as response by response surface methodology (RSM). The RSM used central composite design (CCD) method consists of 30 runs to obtain the actual responses. The actual responses were fitted with the second order algebraic polynomial equation to select a model (suggested model). The suggested model was validated by a few numbers of excellent statistical evidences in analysis of variance (ANOVA). The used evidences include high Fvalue (143.12), very low P-value (<0.0001), non-significant lack of fit, the determination coefficient (R2 = 0.99) and the adequate precision (47.067). To visualize the optimum, the validated model simulated the condition of variables and response (photo degradation %) by a few number of three dimensional plots (3D). To confirm the model, the optimums were performed in laboratory. The results of performed experiments were quite close to the predicted values. In conclusion, the study indicated that the model is successful to simulate the optimum condition of o-cresol photo degradation under visible-light irradiation by manganese doped ZnO nanoparticles.