Examinando por Autor "Paredes-García, Verónica"
Mostrando 1 - 8 de 8
Resultados por página
Opciones de ordenación
Ítem Co°superparamagnetic nanoparticles stabilized by an organic layer coating with antimicrobial activity(Royal Society of Chemistry, 2020-09) Santana, Paula A.; Castillo, Carolina A.; Michea, Sebastián A.; Venegas-Yazigi, Diego; Paredes-García, VerónicaCobalt (Co) is one of the most promising materials in nanotechnology due to its superior magnetic properties. However, due to the high cytotoxicity of cobalt, the activity in biological systems has been little studied. In this work, we report the structural, morphological, and magnetic properties of cobalt nanoparticles stabilized with an organic layer (Co0@C-NPs) and its potential antimicrobial activity. The Co0@C-NPs were obtained from solvothermal conditions and characterized by X-ray powder diffraction, electronic microscopy, and magnetic measurements. The organic layer was analysed by thermogravimetric analysis, Scanning Electron Microscopy, Energy Dispersive Spectrometer, and Fourier Transform Infrared Spectroscopy. From the TEM image, an organic coating layer is observed around Co0where this coating prevents NPs from oxidation allowing it to remain stable until 400 °C. Surface composition studies by SEM/EDS allowed the identification of carbon, oxygen, and cobalt elements present in the organic layer. This result was corroborated later by FITR analysis. Preliminary antibacterial properties were also investigated, which showed that the cobalt nanoparticles are active againstStaphylococcus aureusafter 1 h of exposure. The superparamagnetic properties and organic coating Co0@C-NPs could be biocompatible with biological systems, but more research is needed to apply these nanoparticles in biomedical products. © The Royal Society of Chemistry 2020.Ítem First copper(ii) phase M′0.2Mn0.8PS3·0.25H2O and analogous M′ = CoII, NiII and ZnII materials obtained by microwave assisted synthesis(Royal Society of Chemistry, 2015-07) Fuentealba, Pablo; Cortés, Catalina; Audebrand, Nathalie; Le Fur, Eric; Paredes-García, Verónica; Venegas-Yazigi, Diego; Manzur, Jorge; Spodine, EvgeniaM′0.2Mn0.8PS3·0.25H2O materials are obtained by a mild microwave assisted reaction (M′ = CoII, NiII, CuII, ZnII), which permitted us to obtain the first copper(ii) bimetallic phase. All these materials have a lower energy gap and antiferromagnetic interactions with lower values of the Weiss constant, than that of the pristine phase MnPS3. © The Royal Society of Chemistry.Ítem Novel Linear Trinuclear CuII Compound with Trapped Chiral Hemiaminal Ligand: Magnetostructural Study(Multidisciplinary Digital Publishing Institute (MDPI), 2023-07) Cruz, Carlos; Audebrand, Nathalie; Páez-Hernández, Dayán; Paredes-García, VerónicaA new trinuclear CuII compound {[Cu3(HL′)2(H2O)2](ClO4)4}·(H2O)4 (1) was obtained and presented a trapped chiral hemiaminal (HL2′ = [(5-amino-4H-1,2,4-triazol-3-yl)amino](1H-imidazol-4-yl)methanol)). Compound 1 shows an almost flat cationic structure [Cu3(HL′)2(H2O)2]4+ with a Cu3 linear core reached by the double Cu-OR/NN-Cu triazole/alkoxo bridge of the hemiaminal molecule. The CuII spin carriers are antiferromagnetically coupled, presenting a spin doublet ground state (S = 1/2) with a magnetic coupling constant of −179 cm−1. Moreover, DTF calculations show that the planarity of the compound permits a sigma-type overlapping between the unpaired electrons of the spin carriers and the p-type orbitals of the coordinated N and O atoms producing an electronic delocalization through the bridging ligand responsible for the strong antiferromagnetic interactions observed experimentally. © 2023 by the authors.Ítem One pot solvothermal synthesis of organic acid coated magnetic iron oxide nanoparticles(2014 Sociedad Chilena de Química, 2013) Paredes-García, Verónica; Toledo, Néstor; Juliano, Denardin; Venegas-Yazigi, Diego; Cruz, CarlosABSTRACT In this work we present the synthesis and characterization of iron oxide nanoparticles (IONPs), which were structurally and magnetically characterized. The use of iron salts and an organic acid (l-serine or ascorbic acid) as precursors under solvothermal conditions yielded these coated IONPs. The powder X-ray diffraction pattern of FeO-1 and FeO-2 is consistent with hematite (α-Fe2O3) and hematite-maghemite ((α-Fe2O3/γ-Fe2O3) respectively. The TEM analysis permits to estimate an average size of 10 nm for the FeO-1 sample. The magnetic characterization of the samples through the M(H) plots showed a very low coercivity value for both samples, being 53 Oe for FeO-1 and 10 Oe for FeO-2, indicating the very weak ferromagnetic character of the synthesized iron oxide species. Even though both organic acids under solvothermal conditions permit to obtain coated IONPs in one pot reaction, l-serine produces a more narrow-size distribution.Ítem Spin Frustrated Pyrazolato Triangular CuII Complex: Structure and Magnetic Properties, an Overview(MDPI, 2023-06) Cañón-Mancisidor, Walter; Hermosilla-Ibáñez, Patricio; Spodine, Evgenia; Paredes-García, Verónica; Gómez-García, Carlos J.; Venegas-Yazigi, DiegoThe synthesis and structural characterization of a new triangular Cu3–μ3OH pyrazolato complex of formula, [Cu3(μ3−OH)(pz)3(Hpz)3][BF4]2 (1−Cu3), Hpz = pyrazole, is presented. The triangular unit forms a quasi-isosceles triangle with Cu–Cu distances of 3.3739(9), 3.3571(9), and 3.370(1) Å. This complex is isostructural to the hexanuclear complex [Cu3(μ3−OH)(pz)3(Hpz)3](ClO4)2]2 (QOPJIP). A comparative structural analysis with other reported triangular Cu3–μ3OH pyrazolato complexes has been carried out, showing that, depending on the pyrazolato derivative, an auxiliary ligand or counter-anion can affect the nuclearity and/or the dimensionality of the system. The magnetic properties of 1−Cu3 are analyzed using experimental data and DFT calculation. A detailed analysis was performed on the magnetic properties, comparing experimental and theoretical data of other molecular triangular Cu3–μ3OH complexes, showing that the displacement of the μ3−OH− from the Cu3 plane, together with the type of organic ligands, influences the nature of the magnetic exchange interaction between the spin-carrier centers, since it affects the overlap of the magnetic orbitals involved in the exchange pathways. Finally, a detailed comparison of the magnetic properties of 1−Cu3 and QOPJIP was carried out, which allowed us to understand the differences in their magnetic properties. © 2023 by the authors.Ítem Structural and electronic properties of Polyoxovanadoborates containing the [V 12 B 18 O 60 ] core in different mixed valence states(MDPI Multidisciplinary Digital Publishing Institute, 2015-09) Hermosilla-Ibáñez, Patricio; Muñoz-Becerra, Karina; Paredes-García, Verónica; Fur, Eric Le; Spodine, Evgenia; Venegas-Yazigi, DiegoThis review summarizes all published data until April 2015 related to crystalline lattices formed by the [V 12 B 18 O 60 ] core, which generates polyanionic clusters with different degrees of protonation and mixed-valence ratios. The negative charge of this cluster is counterbalanced by different cations such as protonated amines, hydronium, and alkaline, and transition metal ions. The cluster is shown to form extended 1D, 2D, or 3D frameworks by forming covalent bonds or presenting hydrogen bond interactions with the present secondary cations. These cations have little influence on the solid state reflectance UV-visible spectra of the polyanionic cluster, but are shown to modify the FT-IR spectra and the magnetic behavior of the different reported species. ©. © 2015 by the authors.Ítem Substitution effect on the charge transfer processes in organo-imido lindqvist-polyoxomolybdate(MDPI, 2018-12) Hermosilla-Ibáñez, Patricio; Wrighton-Araneda, Kerry; Cañón-Mancisidor, Walter; Gutiérrez-Cutiño, Marlen; Paredes-García, Verónica; Venegas-Yazigi, DiegoTwo new aromatic organo-imido polyoxometalates with an electron donor triazole group ([n-Bu4N]2[Mo6O18NC6H4N3C2H2]) (1) and a highly conjugated fluorene ([n-Bu4N]2[Mo6O18NC13H9]) (2) have been obtained. The electrochemical and spectroscopic properties of several organo-imido systems were studied. These properties were analysed by the theoretical study of the redox potentials and by means of the excitation analysis, in order to understand the effect on the substitution of the organo-imido fragment and the effect of the interaction to a metal centre. Our results show a bathochromic shift related to the charge transfer processes induced by the increase of the conjugated character of the organic fragment. The cathodic shift obtained from the electrochemical studies reflects that the electronic communication and conjugation between the organic and inorganic fragments is the main reason of this phenomenon. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.Ítem Toward a Rational Design of 3d-4f Heterometallic Coordination Polymers based on Mixed Valence Copper Centers(American Chemical Society, 2019-12) Cruz, Carlos; Rubio, Francisco; Venegas-Yazigi, Diego; Audebrand, Nathalie; Calers, Christophe; Spodine, Evgenia; Paredes-García, VerónicaIn the present work, we report two new CuI/CuII-GdIII mixed valence heterometallic coordination polymers (HCP), [Gd(H2O)4CuIICuI(IDC)2] (1) and [Gd2(H2O)2(C2O4)2CuII(IDC)2CuI 2(4,4′-bipy)]·4.5H2O (2) obtained under solvothermal synthesis using 1H-imidazole-4,5-dicarboxylic acid (H3IDC) as a principal N,O-bifunctional organic linker. In both compounds, the stabilization of the CuI cations is achieved only by the coordination of N-Atoms belonging to the organic ligands. While 1 presents a two-dimensional honeycomb network obtained by the coordination of single organic linker (IDC3-), 2 contains three different organic ligands (IDC3-, C2O4 2-, and 4,4′-bipy), which allow the construction of a three-dimensional network. From a magnetic point of view, 1 and 2 behave as simple paramagnets at high temperature, presenting ferromagnetic interactions below 50 K, and a positive magnetic coupling constant of J = 0.60 cm-1 and J = 0.22 cm-1 was obtained for 1 and 2 respectively. To the best our knowledge, 1 and 2 correspond to the second and third reported examples containing a CuI/CuII mixed valence system assembled with GdIII cations, thus enriching the chemistry involved in 3d-4f metal-organic materials. Copyright © 2019 American Chemical Society.