Scielo RSS <![CDATA[Journal of the Chilean Chemical Society]]> vol. 60 num. 3 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>APPLICATION OF MULTIVARIATE IMAGE ANALYSIS IN QSPR STUDY OF p<i>K</i><sub>a</sub> OF VARIOUS ACIDS BY PRINCIPAL COMPONENTS-LEAST SQUARES SUPPORT VECTOR MACHINE</b>]]> A new implemented quantitative structure-property relationships (QSPR) method, whose descriptors achieved from bidimensional images, was suggested for the predicting of acidity constant (pKa) of various acid. The resulted descriptors were subjected to principal component analysis (PCA) and the most significant principal components (PCs) were extracted. Multivariate image analysis applied to QSPR modeling was done by means of principal component-least squares support vector machine (PC-LSSVM) methods. The resulted model showed high prediction ability with root mean square error of prediction of 0.0195 for PC-LSSVM. <![CDATA[<b>SELF-DECOMPOSITION EFFECT OF GRAPHENE BASED CdSe COMPOSITES FOR ORGANIC DYE IN DARK</b>]]> Herein we obtain CdSe-TiO2 composite, graphene-CdSe composite and graphene-TiO2 composite by using a facile hydrothermal method. The as-prepared composites are characterized by Brunauer emmett Teller (BET) surface area measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS). According to the decomposition results of methylene blue (MB) solution in dark, it can be observed that the graphene-CdSe composites show a very interesting character, self-decomposition effect of MB in dark. <![CDATA[<b>AN ECO-FRIENDLY ONE-POT SYNTHESIS OF 4,4'-(ARYLMETHYLENE)BIS(1H-PYRAZOL-5-OLS) USING [Et<sub>3</sub>NH][HSO<sub>4</sub>] AS A RECYCLABLE CATALYST</b>]]> A simple and efficient procedure for synthesis of 4,4'-(arylmethylene)bis(1H-pyrazol-5-ols) by one-pot three-component condensation of aromatic aldehydes, ethyl acetoacetate, and phenylhydrazine/hydrazine hydrate under solvent-free conditions in the presence of [Et3NH][HSO4] as catalyst is described. The present protocol offers several advantages such as using a reusable and cost-effective ionic liquid, high yields, simple procedure, easy work-up and eco-friendly reaction conditions. <![CDATA[<b>SYNTHESIS, STRUCTURES, AND ANTIBACTERIAL ACTIVITIES OF 3-CHLORO-N'-(2-HYDROXY-5-METHOXYBENZYLIDENE)BENZOHYDRAZIDE AND N'-(2-HYDROXY-5-METHOXYBENZYLIDENE)-3-METHYLBENZOHYDRAZIDE</b>]]> By reaction of 5-methoxysalicylaldehyde with 3-chlorobenzohydrazide and 3-methylbenzohydrazide, respectively, two structurally similar hydrazone compounds, 3-chloro-N'-(2-hydroxy-5-methoxybenzylidene)benzohydrazide (1) and N'-(2-hydroxy-5-methoxybenzylidene)-3-methylbenzohydrazide (2), were synthesized. The compounds were characterized by elemental analyses, infrared and UV-vis spectra, and single crystal X-ray diffraction. The crystal of 1 crystallizes in monoclinic space group P2/n, with unit cell dimensions a = 5.8872(8) Å, b = 31.649(2) Å, c = 7.6309(9) Å, β = 94.427(2)°, V = 1417.6(3) ų, Z = 4, R1 = 0.0462, wR2 = 0.1053. The crystal of 2 crystallizes in orthorhombic space group Pbca, with unit cell dimensions a = 10.415(1) Å, b = 9.781(1) Å, c = 29.548(2) Å, V = 3010.2(5) ų, Z = 8, R1 = 0.0519, wR2 = 0.1577. The compounds were assayed for antibacterial (Bacillus subtilis, Escherichia coli, Pseudomonas fluorescence and Staphylococcus aureus) and antifungal (Aspergillus niger and Candida albicans) activities by MTT method. <![CDATA[<b>SILICA SUPPORTED THALLIUM (III) NITRATE</b>: <b>AN EFFECTIVE OXIDANT FOR OXIDATION OF ALCOHOLS TO THE CARBONYL COMPOUNDS</b>]]> Thallium (III) Nitrate Supported on Silica gel was found to be an efficient reagent system for oxidation of primary and secondary alcohols to their corresponding carbonyl compounds under mild conditions. The striking features of our method are: short reaction times, formation of no over oxidation products due to high selectivity and mild nature of oxidant, easy work-up procedure, high yields and carbon carbon double or triple bond functional group in the alcohol structure does not oxidize to other group. <![CDATA[<b>PHOSPHORUS PROMOTED SO<sub>4</sub><sup>2-</sup>/TiO<sub>2</sub> SOLID ACID CATALYST FOR ACETALIZATION REACTION</b>]]> A novel phosphorus modified SO4(2-)/TiO2 catalyst was synthesized by a facile coprecipitation method, followed by calcination. The catalytic performance of this novel solid acid was evaluated by acetalization. The results showed that the phosphorus was very efficient to enhance the catalytic activity of SO4(2-)/TiO2. The solid acid owned high activity for the acetalization with the yields over 90%. Moreover, the solid acid could be reused for six times without loss of initial catalytic activities. <![CDATA[<b>DEVELOPMENT OF ANTIBACTERIAL MtCu/PLA NANOCOMPOSITES BY CASTING METHOD FOR POTENTIAL USE IN FOOD PACKAGING</b>]]> Polylactic acid (PLA) nanocomposites with two antimicrobial agents based on copper modified montmorillonite (MtCu2+ and MtCu0) were developed in order to obtain a lower environmental impact material with antimicrobial activity for potential use in food packaging. Clay modification was permorfed by cation exchange between MtNa+ and a copper salt obtaining MtCu2+ and its followed reduction with NaBH4 obtaining MtCu0. Then PLA nanocomposite films (MtCu2+/ PLA and MtCu0/PLA), using different concentration of MtCu2+ and MtCu0 (1, 3 and 5 wt.%) were obtained by casting technique. X-ray diffraction (XRD) and Transmission electronic microscopy (TEM) analysis evidenced a certain degree of intercalation of the modified clays in the nanocomposites. Thermal, mechanical and optical properties showed variations by incorporating MtCu2+ and MtCu0 in the polymer matrix. On the other hand, it was possible to evidence antimicrobial activity of the nanocomposites (ASTM Standard E2149) against to Escherichia coli ATCC 25922 and Listeria innocua ATCC 33090 obtaining a 99% maximum of reduction to both bacteria. <![CDATA[<b>SYNTHESIS, CRYSTAL STRUCTURE, DFT AND ANTIBACTERIAL ACTIVITY STUDIES OF (E)-2-BENZYL-3-(FURAN-3-YL)-6,7-DIMETHOXY-4-(2-PHENYL-1H-INDEN-1-YLIDENE)-1,2,3,4-TETRAHYDROISOQUINOLINE</b>]]> The title compound (I), (E)-2-benzyl-3-(furan-3-yl)-6,7-dimethoxy-4-(2-phenyl-1H-inden-1-ylidene)-1,2,3,4-tetrahydroisoquinoline (C37H31NO3), was synthesized and structurally characterized by elemental analysis, ¹H NMR and 13C NMR and single crystal X-ray diffraction. In the compound, the N-containing six-membered ring of the tetrahydroisoquinoline unit adopts a distorted half-chair conformation. In the crystal structure, supramolecular chains mediated by C-H…O contacts along the b-axis are linked into a double layer via C-H…π hydrogen bonds. The resulting double layer stacks along the c-axis without any specific interactions. The molecular geometry was also optimized using density functional theory using (DFT/B3LYP) method with the 6-311G(d,p) basis set and compared with the experimental data. In addition to the optimized geometrical structure, molecular orbital, molecular electrostatic potential (MEP) and chemical reactivity studies of the compound have been investigated by using DFT. The antibacterial activity of the compound for various concentrations were determined against eight test pathogens Bacillus cerus, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Acinetobacter baumannii, Staphylococcus epidermidis, Klebsiella pneumoniae and Proteus vulgaris. The results revealed that the compound exhibited good to moderate antibacterial activity. <![CDATA[<b>SYNTHESIS OF NEW 1,3-THIAZOLE DERIVATIVES; USING 1-(4-CARBAMOYLPHENYL)-3-METHYLTHIOUREA AND 1-METHYL-3-(QUINOLIN-8-YL) THIOUREA AS STARTING MATERIALS</b>]]> A series of novel 1,3-thiazoles have been synthesized in good yields, using dialkyl acetylenedicarboxylate, benzamide and quinoline derivatives of thiourea in ethanol. <![CDATA[<b>CHARACTERIZATION OF THE ANTIFUNGAL ACTIVITY AGAINST <i>BOTRYTIS CINEREA</i> OF SCLAREOL AND 13-<i>EPI</i>-SCLAREOL, TWO LABDANE-TYPE DITERPENOIDS</b>]]> The antifungal activity of Sclareol and 13-epi-Sclareol, two labdane-type diterpenoids, on mycelial growth of the phytopathogenic fungus Botrytis cinerea was evaluated. Diterpenoid fungitoxicity was assessed using the radial growth test method. Both diterpenoids inhibited the mycelial growth of B. cinerea in solid medium; however the inhibitory activity of Sclareol was slightly higher than 13-epi-Sclareol with IC50 value of 237.6 μg/mL and 268.8 μg/mL, respectively. On the other hand, both labdane-type diterpenoids did not alter the plasmatic membrane integrity; however the oxygen consumption of B. cinerea germinating conidia was affected. The evidence suggests that action mechanism of these molecules would be related to the uncoupling of mitochondrial oxidative phosphorylation. Finally, biotransformation of Sclareol by B. cinerea was analysed and the main biotransformed metabolite was identified as 3ß-hydroxysclareol. <![CDATA[<b>SYNTHESIS AND ELECTRICAL CHARACTERIZATION OF ZINC STANNATE (ZTO) PREPARED BY HYDROTHERMAL METHOD</b>]]> Zinc Stannate was prepared at 200 °C by hydrothermal method. The X-Ray diffraction data indicate the obtained compound crystallized in the Fd3m space group characteristic of a cubic spinel structure. SEM-EDX and backscattered electrons show and confirm the purity and homogeneity of the final sample. The ZTO pressed pellet, sintered at 825 °C, for 1 h, reveals a single, slightly flattened, impedance semicircle and homogeneous electrical microstructure. <![CDATA[<b>SYNTHESIS, CRYSTAL STRUCTURES AND PRELIMINARY ANTIBACTERIAL ACTIVITIES OF NICKEL(II) AND ZINC(II) COMPLEXES DERIVED FROM 2-BROMO-6-[(3-CYCLOHEXYLAMINOPROPYLIMINO) METHYL]PHENOL</b>]]> Two centrosymmetric mononuclear nickel(II) and zinc(II) complexes, [NiL2]-2NO3 (1) and [ZnL2(dca)2] (2), where L is the zwitterionic form of 2-bromo-6-[(3-cyclohexylaminopropylimino)methyl]phenol, and dca is the dicyanamide anion, have been synthesized. The complexes have been characterized by physico-chemical methods and single crystal X-ray determination. Complex (1) crystallizes in the monoclinic space group P2Jn with unit cell dimensions a = 7.0091(7) Å, b = 11.137(1) Å, c = 23.997(2) Å, β = 97.390(3)°, V = 1857.7(3) ų, Z = 2, R1 = 0.0617, and wR2 = 0.1632. Complex (2) crystallizes in the triclinic space group P-1 with unit cell dimensions a = 8.762(1) Å, b = 10.386(1) Å, c = 10.687(2) Å, α = 85.209(2)°, β = 83.931(2)°, g = 88.734(2)°, V = 963.6(2) ų, Z = 1, R1 = 0.0374, and wR2 = 0.0873. The Ni atom in (1) is in a square planar geometry, and the Zn atom in (2) is in an octahedral geometry. The preliminary antibacterial activities of the complexes were assayed. <![CDATA[<b>ESSENTIAL OIL CHEMICAL COMPOSITIONS OF THE FRUIT AND SEEDS OF THE ENDEMIC SPECIES <i>PYCNOCYCLA BASHAGARDIANA</i> MOZAFF</b>]]> The essential oil contents in the fruits and the seeds of the endemic species Pycnocycla bashagardiana growing wild in south of Iran was found to be 0.2 % and 0.4% respectively based on the fresh weight. The oils were analyzed by gas chromatography (GC) and GC-mass spectrometry (GC-MS). Twelve and thirty constituents were identified, which approximately constituted 90.5% and 94.0% of the fruits and the seeds oils, respectively. The phenyl propanoid myristicin was found to consist more than 65 % of both oils. <![CDATA[<b>NEW FLUORESCENT CROSSLINKED AROMATIC POLYAMIDES CONTAINING THIOPHENEAND FURANE IN THEIR BACKBONE</b>]]> New fluorescent crosslinked aromatic polyamides containing phenylen, thiophene and furane groups in the main chain were synthesized by self-condensation from 3-(5-aminothiophen-2-yl)propenoic acid, 3-(5-aminofuran-2-yl)propenoic acid and 3-(4-((5-aminothiophen-2-yl)methyleneamino)phenyl)propenoic acid using the phosphorylation method and triphenylphosphite as initiator. The amino compounds were obtained from 3-(5-nitrothiophen-2-yl)propenoic acid, 3-(5-nitrofuran-2-yl)propenoic acid and 3-(4-((5-nitrothiophen-2-yl)methyleneamino)phenyl)propenoic by selective reduction of each nitro group and was confirmed by ¹H-NMR and FT-IR spectroscopy. Crosslinking of polyamides ocurr by mechanism between vinyl side groups reacts with the vinyl carbon of another chain, giving rise to interchain linear crosslinking. Depending on the structure the polymers have higher degree of crosslinking. Some vinyl groups react by thermal treatmentat 200 °C. Partially crosslinked polyamides with high emission fluorescence were obtained. Consequently amide bond formation, crosslinking and conjugation are the main factors that influence the fluorescence process. While polymers have several factors that affect the fluorescence, we believe that the most significant is the crosslinking of vinyl bonds. Subsequent thermal treatment of polyamides provoked crosslinking increase and fluorescence loss. The effect of the chemical structure was correlated with the thermal decomposition. Polyamides were characterized by UV-visible, FT-IR and ¹H-NMR spectroscopy, inherent viscosity and thermogravimetric analysis (TGA). The synthesized polyamides exhibited potential for heat sensitive devices application since the fluorescence can be activated or quenched according to a heating process. <![CDATA[<b>STABILITY OF ARSENIC DURING SOIL TREATMENT AND STORAGE</b>]]> There are many studies in the area of identifying and measuring arsenic (As) and its species in soil samples. However, stability of total As, As(V) and As(III) during sample drying and storage has received little attention. The present study evaluates the stability of total As, As(V) and As(III) in four soils with differing agricultural uses and physicochemical properties. Moisture elimination conditions were evaluated, i.e. lyophilization for 1 day vs. drying at 50°C for 3 days, along with different storage conditions, i.e. room temperature for 2 days vs. -20°C for 2 days. The results show that the recovered levels of native As(V) and As(III) are highest using lyophilization and storage at -20°C. Under these optimal conditions, total As content and the levels of As(V) and As(III) remain stable up to 10 days of storage with an error of ±20%. <![CDATA[<b>DEVELOPMENT OF A SIMPLE AND SPECIFIC UHPLC ASSAY FOR THE DETERMINATION OF ARIPIPRAZOLE AND DEHYDROARDPDPRAZOLE IN RAT PLASMA</b>]]> A new, simple, specific, and rapid ultra high performance liquid chromatography method was developed and validated for the determination of aripiprazole and its active metabolite dehydroaripiprazole in rat plasma. The analysis was performed on a Zorbax Eclipse Plus C18 (50 mm × 2.1 mm, 1.8 μm particles) column using gradient elution with a mobile phase consisting of acetonitrile and acetate buffer (30 mM, pH 5). Plasma samples were analyzed after a simple, one-step protein precipitation with acetonitrile. The method was validated and the specificity, linearity, limit of detection, limit of quantitation, precision, accuracy, recoveries, matrix effect, stability and robustness were determined. The analytes and internal standard were separated in 3.5 min and the total analysis time including the clean-up step was 8 min. Limit of detection was 0.012 μg mL-1 and 0.009 μg mL-1 for aripiprazole and dehydroaripiprazole, respectively. Limit of quantitation was 0.039 μg mL-1 and 0.029 μg mL-1 for aripiprazole and dehydroaripiprazole, respectively. The intra- and inter-day assay variability was less than 2% for the analytes. The proposed method is rapid, reproducible and accurate to quantify both aripiprazole and dehydroaripiprazole. It involves a simple plasma deproteination technique using one step protein precipitation with acetonitrile. This validated method was successfully used to quantify plasma concentrations of the analytes in rat plasma. <![CDATA[<b>REMOVAL OF METAL IONS FROM BÍO BÍO RIVER WATER BY LIQUID-PHASE POLYMER-BASED RETENTION TECHNIQUE</b>]]> Water-soluble poly(2-acrylamidoglycolic acid) (PAAG) was synthesized by radical polymerization and characterized by FTIR spectroscopy and Potentiometrie titration. Subsequently, this polymer was used as extracting reagent of metal ions using LPR technique, through washing and enrichment methods. By the washing method, the selective retention (100 %) of Al3+ was obtained at pH 2.36. The removal of monovalent and divalent ions was maximum for all the metal ions at pH 5. The maximum retention capacity of some metal ions by PAAG was studied by enrichment method using water of Bío Bío river containing metal ions. The higher retention percentage for Al3+ ion indicates that PAAG could be used as an extracting reagent for Al3+ ions from Bío Bío river samples. <![CDATA[<b>A Cu(II) POLYMERIC COMPLEX SURVEYING TRIETHANOLAMINE AND 1,2-DI(4-PYRIDYL)ETHYLENE AS BRIDGING LIGANDS</b>]]> We report the synthesis and crystal structure of a copper (II) polymeric complex (I) prepared by reaction of Cu(ClO4)2 ·5H2O with H3tea (triethanolamine,) and dpe (1,2-di(4-pyridyl)ethylene). in ethanol. The compound is made up of two well differentiated substructures, the first one being a cationic 1D polymer balanced by ClO4- counteranions {[Cu2(H2tea)2(dpe)]·(ClO4)2}n and the second one made is up of two dimers of different occupancies and charge content, viz., [Cu2(Htea)2(dpe)] (neutral, 64% occupancy) and [Cu2(H2tea)2(dpe)]2+ (cationic, 36% occupancy), this latter fraction balancing the charge introduced by ClO4- anions with 72% occupancy. Both substructures differ in that the Hm tea anions in the dimers (m = 1,2) do not bridge cations as their homologue H2tea does in the polymer, but chelate instead one single Cu each. As shown in scheme. The structure of (I) is compared with its close relative [Cu2(H2tea)2(dpe)]·(bpe)·(ClO4)2·H2O (II), where the same original constituents assemble in a slightly different way¹. <![CDATA[<b>KINETICS AND MECHANISTIC STUDY OF OXIDATION OF AMOXICILLIN BY CHLORAMINE-T IN ACID MEDIUM</b>]]> This spectroscopic study presents the kinetics and degradation pathways of oxidation of amoxicillin (AMOX) by chloramines-T (CAT) in acidic medium at a constant ionic strength of 0.105 mol dm-3 at 298 K. Reaction between AMOX and CAT in acidic medium exhibits 1:1 stoichiometry (AMOX:CAT). The reaction is of a first-order in both [CAT] and [AMOX]. The order with respect to acid concentration was fractional. The effects of added products, ionic strength and dielectric constant have been studied. The main oxidation product of AMOX was identified by IR, ¹H NMR and mass spectra. The reaction constants involved in the different steps of the mechanisms were calculated. Activation parameters with respect to slow step of the mechanisms were computed and discussed. <![CDATA[<b>RAPID METHOD OF FRIEDEL-CRAFTS ALKYLATION OF PHLOROGLUCINOL BY MICROWAVE IN DRY MEDIA AND REUSABLE CATALYST</b>]]> A new rapid and efficient method for the synthesis of a series of alkylated phloroglucinols using conventional microwave is reported 4 phloroglucinol derivatives (4, 5, 6 and 7) were synthesized with good yields (~50%) by a Friedel-Crafts reaction through an Electrophilic Aromatic Substitution mechanism between geraniol/prenol and phloroglucinol, using reusable SiO2 and AgNO3 as the best catalyst tested without solvents under microwave irradiation. <![CDATA[<b>SYNTHESIS, SPECTRAL CHARACTERIZATION AND THERMAL BEHAVIOUR OF NEW METAL(II) COMPLEXES WITH SCHIFF BASE DERIVED FROM AMOXICILLIN</b>]]> Metal complexes of Schiff base derived from different antibiotics are widely employed as biological active materials, especially as antibacterial agents. Two new metal (II) complexes with the Schiff, base (HL) derived from amoxicillin and salicylaldehyde were synthesized and investigated using elemental analysis, spectroscopic techniques (IR and UV-Vis), conductometric and magnetic measurements. The IR spectra illustrated a bidentate ligand which coordinates through phenolic oxygen atom and imino nitrogen atom from azomethine bond. UV-Vis spectrophotometry showed the characteristic adsorption bands corresponding to an octahedral geometry for both metal complexes. The general formula established from experimental data was found to be [ML2(H2O)2] (M=Co(II) and Ni(II)). This composition was further confirmed by thermal analysis and their thermal stability in nitrogen atmosphere was investigated. Antibacterial study showed that the efficiency of metal complexes is higher than the one found for the free Schiff base ligand. <![CDATA[<b>SYNTHESES AND CHARACTERIZATIONS OF COPPER COMPLEXES</b>: <b>INTERACTION OF COPPER ACETATE DIHYDRATE WITH 4,4´-BIPYRIDINE</b>]]> Two complexes have been synthesized through the reaction of copper(II) acetate dihydrate with 4,4´-bipyridine. Both were characterized by elemental analysis, magnetic moment, FT-IR spectroscopy, and thermogravimetric analysis. Semiempirical structural DFT studies of [Cu2(CH3COO)4(4,4.bipy)2]n and 4,4´ bipyridine were carried out. 4,4´-Bipyridine acts as bidentate ligand, breaking the Cu2(CH3COO)4 unit and acting as bridge between the metal centers, yielding a polymeric structure bearing monodentate acetate groups. The compounds [Cu2(CH3COO)4(4,4-bipy)2]n and [Cu2(CH3COO)4(4,4-bipy)2(H2O)2]n have magnetic moments of 1.83 and 1.77 B.M, respectively. These values are higher than those of copper (Il) acetate monohydrate (1.4 B.M). <![CDATA[<b>ANALYTICAL TESTING OF THE INTERFERENCE STANDARD METHOD (IFS) FOR METALS IN WINES BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY</b>]]> An analytical testing study of interference standard method (IFS) for metals in wines with low and high residual sugar by inductively coupled plasma mass spectrometry (ICP-MS) was evaluated. Selection of IFS probes was based on the ions formed in the argon plasma, such as natural 38Ar+ or contaminant like 83Kr+ or also ions provided from the matrix sample (for instance, 13C+). The analytical signal was obtained from ratio between the original signals of the analyte and those of the IFS probe species. The accuracy was confirmed using a t-test statistic for comparison between the concentrations obtained by Flame Atomic Absorption Spectrometry (FAAS) and ICP-MS. In a first study, the IFS effect was analyzed by comparing the correlation coefficients obtained with or without dividing the analytical signal by the IFS. Using the 83Kr+ IFS probe provide always better results in the determination of Fe, Mn and Zn compared to 13C+ and 38Ar+.