Browsing by Author "Manriquez, Juan M."

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    An Improved Synthesis of 3,6-Dihydro-as-indacene
    (2021) RDibdalli, Yuvaraja; Faundez, Rodrigo; Preite, Marcelo; Molins, Elies; Chavez, Ivonne; Amshumali, Mungalimane K.; Morales-Verdejo, Cesar; Manriquez, Juan M.
    This contribution describes an updated synthetic route to 3,6-dihydro-as-indacene along with full characterization of all intermediates. The title compound is prepared by Mannich condensation of 2-methylfuran with formaldehyde and dimethylamine hydrochloride, quaternization of the resulting amine with methyl iodide, and conversion into the ammonium hydroxide salt by treatment with silver oxide in water. Subsequent Hoffmann elimination and [6,6]-cycloaddition through pyrolysis produces a furanocyclophane, which after photooxidation, intramolecular cycloaddition, and dehydration with sodium carbonate affords 2,3,6,7-tetrahydro-1,8-dione-as-indacene. Reduction of this diketone gives a mixture of alcohols, which after dehydration under slightly basic or acidic conditions produces 3,6-dihydro-as-indacene. The structure is confirmed by X-ray diffraction, and all intermediates are characterized by means of H-1 and C-13 NMR spectroscopy.
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    Economical and Simple Preparation of Oleyl Bromide from Commercially Available Olive Oil
    (2017) Preite, Marcelo Daniel; Castillo Suzarte, Francisco Javier; Urbina, Claudia M.; Faúndez Gutiérrez, Rodrigo Esteban; Manriquez, Juan M.; Chávez Madariaga, Ivonne
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    New Rh derivatives of s-indacene active in dehydrogenative silylation of styrene
    (ELSEVIER SCIENCE SA, 2006) Esponda, Edgardo; Adams, Christopher; Burgos, Francisco; Chavez, Ivonne; Manriquez, Juan M.; Delpech, Fabien; Castel, Annie; Gornitzka, Heinz; Riviere Baudet, Monique; Riviere, Pierre
    The mono- and bimetallic complexes [(2,6-diethyl-4,8-dimethyl-s-indacenide){Rh(COD)}] (1), anti-[(2,6-diethyl-4,8-dimethyl-s-indacenediide) {Rh(COD)}(2)] (2a), syn-[(2,6-diethyl-4,8-dimethyl-s-indacenediide){Rh(COD)}(2)] (2b) were synthesized and characterized spectroscopically and in the case of complex 2b, by means of X-ray diffraction. The C-13 and Rh-103 NMR studies suggest that the bonding mode of the indacenediide ligand can be described as intermediate between eta(3)- and eta(5)-coordination. This result was confirmed by the crystal structure of 2b as evidenced by the slippage of the rhodium atom towards the periphery of the ligand. Cyclic voltammetry studies revealed a strong intermetallic communication through the fused ring ligand. This property was further illustrated by higher activity and selectivity of binuclear complexes 2 for the catalytic dehydrogenative silylation of styrene. (c) 2006 Elsevier B.V. All rights reserved.
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    Novel Schiff base iron(ii) phthalocyanine with composite MWCNTs on modified GCE: electrochemical sensor development for paracetamol
    (2022) Mounesh; Reddy, K. R. Venugopala; Yuvaraja, D.; Manriquez, Juan M.; Lokesh, K. S.; Amshumali, M. K.
    The synthesis and characterization of novel peripherally tetra-substituted Schiff base iron(ii) phthalocyanines (iron(ii) (2Z)-2-(3-chlorobenzylidene)hydrazinecarbothiocarboxamide phthalocyanine (FeTClBCTCAPc)) are described for the first time in this study. The Schiff base ligand and FeTClBCTCAPc complex are characterized by a combination of IR, H-1 NMR, mass spectroscopy, XRD, TGA and UV-vis spectroscopy techniques. The stepwise fabrication process of the FeTClBCTCAPc@GC electrode with composite MWCNTs and its electrochemical sensing performance towards paracetamol (PA) was evaluated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and differential pulse voltammetry (DPV). Compared with the MWCNT-modified electrode, the FeTClBCTCAPc@MWCNTs/GC electrode shows a better electrocatalytic activity for the oxidation of PA with lower oxidation potential and larger peak current, so the FeTClBCTCAPc@MWCNTs/GC electrode nanocomposite can be used as an enhanced sensing platform for the electrochemical determination of PA. The kinetic parameters of PA electro-oxidation at FeTClBCTCAPc@MWCNTs/GC electrodes were studied in detail, and the determination conditions were optimized. Under the optimal conditions, the oxidation peak current is linear to the PA concentration in the range (detection limit) 50-900 nM (18.5 nM) for CA, 50-500 nM (20.5 nM) for CV, 50-500 nM (15 nM) for DPV, and 50-500 nM (15.5 nM) for LSV. Based on the high sensitivity, stability and good selectivity of the FeTClBCTCAPc@MWCNTs/GC electrode, the proposed method was successfully applied to the determination of PA in commercial tablet samples, and the satisfactory results confirm the applicability of this sensor in practical analysis.
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    pi-donor/acceptor effect on lindqvist type polyoxomolibdates because of various multiple-bonded nitrogenous ligands
    (AMER CHEMICAL SOC, 2007) Mac Leod Carey, Desmond; Munoz Castro, Alvaro; Bustos, Carlos J.; Manriquez, Juan M.; Arratia Perez, Ramiro
    The electronic structures of Lindqvist type functionalized polyoxometalates (POM) ([Mo6O18R](n-) R = O, NO, NAr, NNAr, NNAr2; n = 2, 3) have been investigated using density functional methods. We discuss the role of the replacement of terminal oxo ligands by pi-donor/acceptor multiple-bonded nitrogenous ligands on the basis of geometrical parameters, charge analyses, reactivity indexes, and vibrational spectra. The calculated reactivity indexes (chemical potential, electronegativity, hardness, and electrophilicity) indicate that the most reactive functionalized POMs are those substituted by pi-acceptor ligands. These pi-acceptor ligands induce a decrease in the hardness and an increase in the chemical potential and electrophilicity, thus increasing the reactivity. Our calculations are in reasonable agreement with reported experimental data.