Inhibition efficiency and adsorption mechanism of 4-aminobenzoic acid for copper corrosion in nitric acid medium: a combined experimental and theoretical investigation

Structural Chemistry - A combined experimental and theoretical study is presented to predict and analyze the inhibition efficiency and adsorption mechanism of 4-aminobenzoic acid molecule for...     

The kinetics study of the reduction of Fast Green dye with cetylpyridinum chloride as cationic surfactant

The kinetics of the reaction of Fast Green dye (FG) with cetylpyridinum chloride was studied in alkaline medium by UV-Visible spectrophotometer. Reduction of Fast Green dye was carried out by varying the fast green dye concentration, cetylpyridinum chloride concentration and concentration of sodium hydroxide. In the present study the reduction of dye was carried out in order to reduce the color content. The interaction of dye was carried out with reducing analyte (cetylpyridinum chloride). The rate of the reaction was determined by varying the above parameters at different temperatures. It was observed that the reduction followed pseudo first-order kinetics with respect to dye, surfactant, OH⁻ ion concentration according to the following reaction pathway. The mechanism for the photo bleaching of the dye has been proposed and well confirmed by the data simulation procedure. The activation parameters of the reaction like entropy of activation (ΔS) and free energy of activation (ΔG) showed the extremely solvated states of transient complex which was less disorderly arranged than the oxidized form of dye, whereas E _a values reflects a high amount of energy required for the reduction of dye with cetylpyridinum chloride.     

Almost Dunford–Pettis sets in Banach lattices

We introduce and study the class of almost Dunford–Pettis sets in Banach lattices. It also discusses some of the consequences derived from this study. As an application, we characterize Banach lattices whose relatively weakly compact sets are almost Dunford–Pettis sets. Also, we establish some necessary and sufficient conditions on which an almost Dunford–Pettis set is L-weakly compact (respectively, relatively weakly compact). In particular, we characterize Banach lattices under which almost Dunford–Pettis sets in the topological dual of a Banach lattice coincide with that of L-weakly compact (respectively, relatively weakly compact) sets. As a consequences we derive some results.     

Development and Characterization of Novel Biopolymer Derived from Abelmoschus esculentus L. Extract and Its Antidiabetic Potential

Abelmoschus esculentus (Okra) is an important vegetable crop, widely cultivated around the world due to its high nutritional significance along with several health benefits. Different parts of okra including its mucilage have been currently studied for its role in various therapeutic applications. Therefore, we aimed to develop and characterize the okra mucilage biopolymer (OMB) for its physicochemical properties as well as to evaluate its in vitro antidiabetic activity. The characterization of OMB using Fourier-transform infrared spectroscopy (FT-IR) revealed that okra mucilage containing polysaccharides lies in the bandwidth of 3279 and 1030 cm⁻¹, which constitutes the fingerprint region of the spectrum. In addition, physicochemical parameters such as percentage yield, percentage solubility, and swelling index were found to be 2.66%, 96.9%, and 5, respectively. A mineral analysis of newly developed biopolymers showed a substantial amount of calcium (412 mg/100 g), potassium (418 mg/100 g), phosphorus (60 mg/100 g), iron (47 mg/100 g), zinc (16 mg/100 g), and sodium (9 mg/100 g). The significant antidiabetic potential of OMB was demonstrated using α-amylase and α-glucosidase enzyme inhibitory assay. Further investigations are required to explore the newly developed biopolymer for its toxicity, efficacy, and its possible utilization in food, nutraceutical, as well as pharmaceutical industries.     

Butylene copolyesters based on aldaric and terephthalic acids. Synthesis and characterization

The synthesis, characterization, and some properties of new copolyesters analogous to poly(butylene terephthalate) (PBT), based on L ‐arabinaric and galactaric acids, are described. These copolyesters were obtained by polycondensation reaction in the melt of mixtures of methyl 2,3,4‐tri‐O‐methyl‐L ‐arabinarate or methyl 2,3,4,5‐tetra‐O‐methyl‐galactarate and dimethyl terephthalate with 1,4‐butanediol. Their weight‐average molecular weights ranged between 10,000 and 34,000, with polydispersities ranging from 1.4 to 2.2. The composition of all the copolymers was analyzed by NMR, and was found to have a statistical microstructure. All these copolyesters were thermally stable, with degradation temperatures well above 300 °C. The melting temperature and crystallinity decreased in both series, and the glass transition temperature increased and decreased respectively, for the PBTGa and PBTAr series with increasing amounts of aldaric units in the copolyester chain. Only PBT‐derived copolyesters containing a maximum of 30% aldaric units showed discrete scattering characteristic of crystalline material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1168–1177, 2009     

Iron,copper and zinc ammonium-1-hydroxyalkylidene-diphosphonates with zero-, one- and two-dimensional covalent metal–ligand structures extended into three-dimensional supramolecular networks by charge-assisted hydrogen-bonding

Hydrothermal synthesis with MCl₂ (M = Fe, Cu, and Zn) and disodium 5-ammonium-1-hydroxypentylidene-1,1-bisphosphonate, (Na⁺)₂[⁺H₃N(CH₂)₄C(OH)(PO₃²⁻)(PO₃H⁻)] (Na₂HAC₅OHP₂) or sodium 3-ammonium-1-hydroxypropylidene-1,1-bisphosphonate hydrate, Na⁺[⁺H₃N(CH₂)₂C(OH)(PO₃H^–)(PO₃H^–)]·H₂O (NaH₂PAM·H₂O) the sodium salt of pamidronic acid, H₃PAM) yielded the one-dimensional (1D) iron, molecular copper and two-dimensional (2D) zinc compounds 1D-{[Fe(μ₃-η⁵-HAC₅OHP₂)]·H₂O}, 1, [Cu(η²-H₂AC₅OHP₂)₂], 2, 2D-{[Zn₂(μ₅-η⁷-AC₅OHP₂)Cl], 3, and 2D-{[Zn(μ₂-η³-H₂PAM)₂], 4, respectively. The bisphosphonate ligand bridges (μ_n) between 2–5 metal atoms and uses 2–7 oxygen donor atoms towards metal coordination (ηⁿ). The zwitterionic nature of the now bis- or tetrakis-deprotonated ammonium–bisphosphonate is retained in the metal complexes. From the reaction of NiCl₂ and Na₂HAC₅OHP₂ the zwitterionic 5-ammonium-1-hydroxypentylidene-1-phosphonic acid, ⁺H₃N(CH₂)₄CH(OH)PO₃H⁻, 5 was obtained as a product of the ligand P–C bond hydrolysis. Adjacent strands, molecules or layers in 1–4, respectively are organized through the Coulomb attraction between the positive ammonium group and the negative phosphonate groups, supported by hydrogen-bonding. Each protic H atom on the C–OH, NH₃⁺ and –PO₃H⁻ group is involved in charge-assisted hydrogen-bonding. The ammonium-pentylidene groups act as hydrophobic separators between the hydrophilic units with the polar M{C(OH)(PO₃)₂} and {NH₃} units. Bond valence sum calculations support the Fe(II) oxidation state in 1, which was experimentally determined from a quantitative polarographic Fe(II)/Fe(III) speciation analysis as well as a temperature variable magnetic study.     

Separation and identification of a new saponin from the flowers of Guaiacum officinale L

A triterpenoid saponin, guaianin O (1), oleanolic acid 3-O-{α-L-rhamnopyranosyl-(1 → 2)-[β-D-glucopyranosyl-(1 → 3)]-α-L-arabinopyranoside}-28- O-[β-D-glucopyranosyl]-ester, was isolated from the n-butanol extract of flowers of Guaiacum officinale L. The structural elucidation of 1 was accomplished by extensive studies of both one and two dimensional 1H, 13C-NMR spectra, the FAB mass spectrum, and alkaline and acid hydrolyses.     

Synthesis,physico-chemical and spectral investigations of novel homo-bimetallic mixed-ligand complexes: 57Fe Mössbauer parameters of [Fe2(imda)2(H2O)3Cl]

The newly prepared homo-bimetallic complexes [M₂(imda)₂(H₂O)₄], [M₂(imda)₂(Bipy)₂] (M = Co, Ni or Cu) and [Fe₂(imda)₂(H₂O)₃Cl] (H₂imda = iminodiacetic acid and Bipy = 2,2′-bipyridine) have been studied employing IR, FAB-mass, ¹H and ¹³C NMR, EPR and ligand field spectra, which indicated a high-spin state of metal ion with hexa-coordinate environment. ⁵⁷Fe Mössbauer data of the homo-bimetallic complex [Fe₂(imda)₂(H₂O)₃Cl] confirm a high-spin configuration with Fe (±3/2 → 1/2) nuclear transitions and the presence of Kramer's double degeneracy. At RT, the spin–spin interactions of the neighbouring nuclei (Fe³⁺–Fe³⁺ = S_5/2–S_5/2) are anti-ferromagnetically coupled. However, at LNT, the complex acquires a mixed-valent [Fe^III–Fe^II] composition corroborated from the X-band EPR data. CV studies indicated the presence of quasi-reversible redox Cu^II/I, Cu^II/III, Fe^III/II, Fe^III/I and Fe^II/I couples.     

Spectral and physico-chemical investigations of novel homo-dinuclear di-μ2-alkoxo bridged Schiff base complexes: 57Fe Mössbauer parameters of the Fe(III) complex

Spectral and molecular model computations on homo-dinuclear complexes [M₂L₂(H₂O)₂Cl₂] [L = 1-(salicylaldeneamino)-3-hydroxypropane, M = Cr³⁺, Mn³⁺, Fe³⁺, Co³⁺, Ni³⁺ or Cu³⁺] are consistent with a distorted hexa-coordinate geometry. X-band EPR spectral data indicated a rhombic distortion around Cu(II) ion. Magnetic moment and ⁵⁷Fe Mössbauer data confirmed a high-spin state electronic configuration (t_2g³e_g², S = 5/2) and asymmetric ligand environment around Fe(III) with nuclear transitions Fe(±3/2 → 1/2) exhibiting Kramer's double degeneracy. The neighboring Fe(III) nuclei in the homo-dinuclear species are antiferromagnetically coupled.