2018 |
Sanchez, B; Calderon, C; Garrido, C; Contreras, R; Campodonico, P R Solvent Effect on a Model Snar Reaction in Ionic Liquid/Water Mixtures at Different Compositions Artículo de revista New Journal of Chemistry, 42 (12), pp. 9645-9650, 2018, ISSN: 1144-0546. Resumen | Enlaces | BibTeX | Etiquetas: aromatic binary-mixtures, catalysis, kinetics liquids, mixed-solvents, molecules, nitro-group, nucleophilic-substitution, preferential solvation, water @article{RN421, title = {Solvent Effect on a Model Snar Reaction in Ionic Liquid/Water Mixtures at Different Compositions}, author = { B. Sanchez and C. Calderon and C. Garrido and R. Contreras and P.R. Campodonico}, url = {/brokenurl#<Go to ISI>://WOS:000435298100034}, doi = {10.1039/c7nj04820c}, issn = {1144-0546}, year = {2018}, date = {2018-01-01}, journal = {New Journal of Chemistry}, volume = {42}, number = {12}, pages = {9645-9650}, abstract = {The reaction of phenyl 2,4,6-trinitrophenyl ether and piperidine was kinetically evaluated in BMIMBF4/water mixtures as the reaction media. This study shows the dramatic effect of the mixture composition on the reacting pair and its reaction rate, highlighting two strongly demarcated zones. The first one, rich in water, is characterized by strong variations in the rate coefficient values, suggesting the presence of preferential solvent effects in the aqueous phase. The second zone shows high rate coefficient values independent of the composition of the solvent mixture, suggesting predominant anion solvent effects. These results were validated using fluorescence spectroscopy and the Kamlet-Taft parameter.}, keywords = {aromatic binary-mixtures, catalysis, kinetics liquids, mixed-solvents, molecules, nitro-group, nucleophilic-substitution, preferential solvation, water}, pubstate = {published}, tppubtype = {article} } The reaction of phenyl 2,4,6-trinitrophenyl ether and piperidine was kinetically evaluated in BMIMBF4/water mixtures as the reaction media. This study shows the dramatic effect of the mixture composition on the reacting pair and its reaction rate, highlighting two strongly demarcated zones. The first one, rich in water, is characterized by strong variations in the rate coefficient values, suggesting the presence of preferential solvent effects in the aqueous phase. The second zone shows high rate coefficient values independent of the composition of the solvent mixture, suggesting predominant anion solvent effects. These results were validated using fluorescence spectroscopy and the Kamlet-Taft parameter. |
2017 |
Orellana, C; Mendizabal, F; González, G; Miranda-Rojas, S; Barrientos-Poblete, L Palmitic Acid and Hexadecylamine Molecules Assdsorbed on Titania Surface in Hybrid Composites. Effect of Surfactants Using Density Functional Theory Artículo de revista Computational and Theoretical Chemistry, 1110 , pp. 50-59, 2017, ISSN: 2210-271x. Resumen | Enlaces | BibTeX | Etiquetas: basis-sets, bsse, calculations, catalysis, clusters, compounds, dft dft, dioxide dispersion enzymatic hexadecylamine, hydrogen-bonds, interactions, laminar n-body noncovalent palmitic photocatalysis properties, sensitized solar-cells, spectroscopic strong term, tio2, titanium @article{orellana2017palmitic, title = {Palmitic Acid and Hexadecylamine Molecules Assdsorbed on Titania Surface in Hybrid Composites. Effect of Surfactants Using Density Functional Theory}, author = { C. Orellana and F. Mendizabal and G. Gonz\'{a}lez and S. Miranda-Rojas and L. Barrientos-Poblete}, url = {/brokenurl#<Go to ISI>://WOS:000401679900007}, doi = {10.1016/j.comptc.2017.04.006}, issn = {2210-271x}, year = {2017}, date = {2017-01-01}, journal = {Computational and Theoretical Chemistry}, volume = {1110}, pages = {50-59}, publisher = {2017 Elsevier B.V.}, abstract = {A complete theoretical characterization of the factors involved in the stabilization of hybrid laminar composites is reported, with the purpose of understanding the main interactions involved in the formation of these types of systems. The models were built using two different surfactants: hexadecylamine (HDA) and palmitic acid (PAc), on a cluster of titania (TiO2) which represents its anatase crystalline phase. We explored the relevance of the titania-surfactant and surfactant-surfactant interactions, and of the protonation state of the palmitic acid in the stabilization of the hybrid laminar composites. The results were rationalized using energy decomposition analysis (EDA) and the non-covalent interaction index (NIC). The interaction energies between HDA and the TiO2 surface without the contribution of the dispersion forces were -25 kcal/mol and -29 kcal/mol for the (1 0 0) and (1 01) surfaces, respectively. These results suggest the formation of a donor-acceptor bond between HDA-TiO2 allowing its stabilization. On the other hand, the interaction energy between PAc and the TiO2 (1 0 1) surface was about -45 kcal/mol without the dispersion term. Thus, the PAc-TiO2 model has a higher covalent character than the HDA-TiO2 interaction, as confirmed by the energy decomposition analyses. The results suggest new hybrid laminar composites which are better when carboxylic acid was used instead of amines. Therefore, the use of surfactants with the carboxyl functional group yielded more stable TiO2 hybrid composites. The interaction energy between surfactant chains was about -13 kcal/mol, confirming the importance of dispersion forces in the stabilization of these types of systems. The study of systems with palmitic acid was complemented by building some anionic models to show the importance of acid protons in those systems. However, when the acidic hydrogens were removed, the interaction energy between the PAc molecules considering the dispersion correction increased to 45 kcal/mol, with a highly repulsive character. These results suggest that the acid hydrogens of the PAc surfactants play a fundamental role in terms of correctly representing the carboxylic acid-TiO2 interface and the stabilization of the laminar hybrid composites.}, keywords = {basis-sets, bsse, calculations, catalysis, clusters, compounds, dft dft, dioxide dispersion enzymatic hexadecylamine, hydrogen-bonds, interactions, laminar n-body noncovalent palmitic photocatalysis properties, sensitized solar-cells, spectroscopic strong term, tio2, titanium}, pubstate = {published}, tppubtype = {article} } A complete theoretical characterization of the factors involved in the stabilization of hybrid laminar composites is reported, with the purpose of understanding the main interactions involved in the formation of these types of systems. The models were built using two different surfactants: hexadecylamine (HDA) and palmitic acid (PAc), on a cluster of titania (TiO2) which represents its anatase crystalline phase. We explored the relevance of the titania-surfactant and surfactant-surfactant interactions, and of the protonation state of the palmitic acid in the stabilization of the hybrid laminar composites. The results were rationalized using energy decomposition analysis (EDA) and the non-covalent interaction index (NIC). The interaction energies between HDA and the TiO2 surface without the contribution of the dispersion forces were -25 kcal/mol and -29 kcal/mol for the (1 0 0) and (1 01) surfaces, respectively. These results suggest the formation of a donor-acceptor bond between HDA-TiO2 allowing its stabilization. On the other hand, the interaction energy between PAc and the TiO2 (1 0 1) surface was about -45 kcal/mol without the dispersion term. Thus, the PAc-TiO2 model has a higher covalent character than the HDA-TiO2 interaction, as confirmed by the energy decomposition analyses. The results suggest new hybrid laminar composites which are better when carboxylic acid was used instead of amines. Therefore, the use of surfactants with the carboxyl functional group yielded more stable TiO2 hybrid composites. The interaction energy between surfactant chains was about -13 kcal/mol, confirming the importance of dispersion forces in the stabilization of these types of systems. The study of systems with palmitic acid was complemented by building some anionic models to show the importance of acid protons in those systems. However, when the acidic hydrogens were removed, the interaction energy between the PAc molecules considering the dispersion correction increased to 45 kcal/mol, with a highly repulsive character. These results suggest that the acid hydrogens of the PAc surfactants play a fundamental role in terms of correctly representing the carboxylic acid-TiO2 interface and the stabilization of the laminar hybrid composites. |
Aliaga, J A; Zepeda, T N; Pawelec, B N; Araya, J F; Antunez-Garcia, J; Farias, M H; Fuentes, S; Galvan, D; Alonso-Nunez, G; González, G Microspherical Res2 as a High-Performance Hydrodesulfurization Catalyst Artículo de revista Catalysis Letters, 147 (5), pp. 1243-1251, 2017, ISSN: 1011-372x. Resumen | Enlaces | BibTeX | Etiquetas: carbon, catalysis, composites, dichalcogenides, disulfide, evolution, heterogeneous hidrodesulfurization, hydrodeoxygenation, hydrogen molybdenum-disulfide, nanoparticles, nanosized rhenium solvothermal sulfide, sulfides, synthesis, technetium transition-metal @article{RN349, title = {Microspherical Res2 as a High-Performance Hydrodesulfurization Catalyst}, author = { J.A. Aliaga and T.N. Zepeda and B.N. Pawelec and J.F. Araya and J. Antunez-Garcia and M.H. Farias and S. Fuentes and D. Galvan and G. Alonso-Nunez and G. Gonz\'{a}lez}, url = {/brokenurl#<Go to ISI>://WOS:000400356200016}, doi = {10.1007/s10562-017-2024-6}, issn = {1011-372x}, year = {2017}, date = {2017-01-01}, journal = {Catalysis Letters}, volume = {147}, number = {5}, pages = {1243-1251}, abstract = {An unsupported microspherical ReS2 catalyst, consisting in self-assembled nano-layers, was evaluated in the hydrodesulfurization (HDS) of 3-methylthiophene showing an excellent catalytic activity. The samples were characterized by X-ray diffraction, scanning electron microscopy, high resolution electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. These techniques revealed that the rhenium disulfide layers are confined to a 3D hierarchical structure with different stacking, slab size and bending, according to the annealing temperature (400 or 800 A degrees C). The presence of a defect-rich structure in the microspheres, with short and randomly-orientated ReS2 slabs, results in the exposure of additional edge sites, which improve the catalytic performance of this material. This microspherical ReS2 composite, with good HDS performance, is a promising catalyst for the desulfurization of fuel oils; the solvothermal reaction conditions are also useful to tune and create exotic morphologies for the design of new ReS2 catalysts.}, keywords = {carbon, catalysis, composites, dichalcogenides, disulfide, evolution, heterogeneous hidrodesulfurization, hydrodeoxygenation, hydrogen molybdenum-disulfide, nanoparticles, nanosized rhenium solvothermal sulfide, sulfides, synthesis, technetium transition-metal}, pubstate = {published}, tppubtype = {article} } An unsupported microspherical ReS2 catalyst, consisting in self-assembled nano-layers, was evaluated in the hydrodesulfurization (HDS) of 3-methylthiophene showing an excellent catalytic activity. The samples were characterized by X-ray diffraction, scanning electron microscopy, high resolution electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. These techniques revealed that the rhenium disulfide layers are confined to a 3D hierarchical structure with different stacking, slab size and bending, according to the annealing temperature (400 or 800 A degrees C). The presence of a defect-rich structure in the microspheres, with short and randomly-orientated ReS2 slabs, results in the exposure of additional edge sites, which improve the catalytic performance of this material. This microspherical ReS2 composite, with good HDS performance, is a promising catalyst for the desulfurization of fuel oils; the solvothermal reaction conditions are also useful to tune and create exotic morphologies for the design of new ReS2 catalysts. |
2016 |
Castillo, C; Buono-Core, G; Manzur, C; Yutronic, N; Sierpe, R; Cabello, G; Chornik, B Molybdenum Trioxide Thin Films Doped with Gold Nanoparticles Grown by a Sequential Methodology: Photochemical Metal-Organic Deposition (Pmod) and Dc-Magnetron Sputtering Artículo de revista Journal of the Chilean Chemical Society, 61 (1), pp. 2816-2820, 2016, ISSN: 0717-9707. Resumen | Enlaces | BibTeX | Etiquetas: catalysis, diffraction, films, moo3, nanostructures, optical-properties, oxidation, oxide-films, oxides, photoelectron resonance, selective size, spectroscopy, sputtering, support, surface-plasmon temperature, thin x-ray xps @article{RN302, title = {Molybdenum Trioxide Thin Films Doped with Gold Nanoparticles Grown by a Sequential Methodology: Photochemical Metal-Organic Deposition (Pmod) and Dc-Magnetron Sputtering}, author = { C. Castillo and G. Buono-Core and C. Manzur and N. Yutronic and R. Sierpe and G. Cabello and B. Chornik}, url = {/brokenurl#<Go to ISI>://WOS:000378145500014}, doi = {10.4067/S0717-97072016000100014}, issn = {0717-9707}, year = {2016}, date = {2016-01-01}, journal = {Journal of the Chilean Chemical Society}, volume = {61}, number = {1}, pages = {2816-2820}, abstract = {Gold nanoparticles (AuNPs) were deposited by DC-magnetron sputtering onto molybdenum trioxide (MoO3) thin films grown by Photochemical Metal-Organic Deposition (PMOD) on Si(100) and borosilicate glass substrates. The chemical, optical and morphology properties of the films were studied by UV/Vis Spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and X-Ray Diffraction (XRD). SEM revealed that AuNPs formed after 5 s of sputtering. AuNPs are spherical and have both an average diameter of 18 nm and a relatively narrow size distribution. As the deposition time increases, larger structures are formed by an aggregation of AuNPs. XPS studies of the AuNP/MoO3 films on Si(100) showed the presence of Mo(VI) and Mo(V), which indicated that the films were primarily non-stoichiometric molybdenum oxides. The occurrence of oxygen vacancies in the substrate play an important role to stabilize the AuNPs.}, keywords = {catalysis, diffraction, films, moo3, nanostructures, optical-properties, oxidation, oxide-films, oxides, photoelectron resonance, selective size, spectroscopy, sputtering, support, surface-plasmon temperature, thin x-ray xps}, pubstate = {published}, tppubtype = {article} } Gold nanoparticles (AuNPs) were deposited by DC-magnetron sputtering onto molybdenum trioxide (MoO3) thin films grown by Photochemical Metal-Organic Deposition (PMOD) on Si(100) and borosilicate glass substrates. The chemical, optical and morphology properties of the films were studied by UV/Vis Spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and X-Ray Diffraction (XRD). SEM revealed that AuNPs formed after 5 s of sputtering. AuNPs are spherical and have both an average diameter of 18 nm and a relatively narrow size distribution. As the deposition time increases, larger structures are formed by an aggregation of AuNPs. XPS studies of the AuNP/MoO3 films on Si(100) showed the presence of Mo(VI) and Mo(V), which indicated that the films were primarily non-stoichiometric molybdenum oxides. The occurrence of oxygen vacancies in the substrate play an important role to stabilize the AuNPs. |
2012 |
Soto-Delgado, J; Aizman, A; Contreras, R; Domingo, L R On the Catalytic Effect of Water in the Intramolecular Diels-Alder Reaction of Quinone Systems: A Theoretical Study Artículo de revista Molecules, 17 (11), pp. 13687-13703, 2012, ISSN: 1420-3049. Resumen | Enlaces | BibTeX | Etiquetas: catalysis, characterization, chemistry density dft dft, diels-alder difference electrophilicity, functionals, index, indices, intramolecular local molecules, polar quantitative reactions, reactivity regioselectivity, solvent, thermochemistry, water @article{sotodelgado2012catalytic, title = {On the Catalytic Effect of Water in the Intramolecular Diels-Alder Reaction of Quinone Systems: A Theoretical Study}, author = { J. Soto-Delgado and A. Aizman and R. Contreras and L.R. Domingo}, url = {/brokenurl#<Go to ISI>://WOS:000311428400087}, doi = {10.3390/molecules171113687}, issn = {1420-3049}, year = {2012}, date = {2012-01-01}, journal = {Molecules}, volume = {17}, number = {11}, pages = {13687-13703}, abstract = {The mechanism of the intramolecular Diels-Alder (IMDA) reaction of benzoquinone 1, in the absence and in the presence of three water molecules, 1w, has been studied by means of density functional theory (DFT) methods, using the M05-2X and B3LYP functionals for exploration of the potential energy surface (PES). The energy and geometrical results obtained are complemented with a population analysis using the NBO method, and an analysis based on the global, local and group electrophilicity and nucleophilicity indices. Both implicit and explicit solvation emphasize the increase of the polarity of the reaction and the reduction of activation free energies associated with the transition states (TSs) of this IMDA process. These results are reinforced by the analysis of the reactivity indices derived from the conceptual DFT, which show that the increase of the electrophilicity of the quinone framework by the hydrogen-bond formation correctly explains the high polar character of this intramolecular process. Large polarization at the TSs promoted by hydrogen-bonds and implicit solvation by water together with a high electrophilicity-nucleophilicity difference consistently explains the catalytic effects of water molecules.}, keywords = {catalysis, characterization, chemistry density dft dft, diels-alder difference electrophilicity, functionals, index, indices, intramolecular local molecules, polar quantitative reactions, reactivity regioselectivity, solvent, thermochemistry, water}, pubstate = {published}, tppubtype = {article} } The mechanism of the intramolecular Diels-Alder (IMDA) reaction of benzoquinone 1, in the absence and in the presence of three water molecules, 1w, has been studied by means of density functional theory (DFT) methods, using the M05-2X and B3LYP functionals for exploration of the potential energy surface (PES). The energy and geometrical results obtained are complemented with a population analysis using the NBO method, and an analysis based on the global, local and group electrophilicity and nucleophilicity indices. Both implicit and explicit solvation emphasize the increase of the polarity of the reaction and the reduction of activation free energies associated with the transition states (TSs) of this IMDA process. These results are reinforced by the analysis of the reactivity indices derived from the conceptual DFT, which show that the increase of the electrophilicity of the quinone framework by the hydrogen-bond formation correctly explains the high polar character of this intramolecular process. Large polarization at the TSs promoted by hydrogen-bonds and implicit solvation by water together with a high electrophilicity-nucleophilicity difference consistently explains the catalytic effects of water molecules. |
Barrientos-Poblete, L; Allende-González, P; Orellana, C; Jara, P Ordered Arrangements of Metal Nanoparticles on Alpha-Cyclodextrin Inclusion Complexes by Magnetron Sputtering Artículo de revista Inorganica Chimica Acta, 380 , pp. 372-377, 2012, ISSN: 0020-1693. Resumen | Enlaces | BibTeX | Etiquetas: catalysis, colloids, gold guest host interaction, magnetron metal metal-guest molecules, monolayer, nanoparticles, nanostructures, particles, size, sputtering, stabilization, supramolecular surface @article{RN81, title = {Ordered Arrangements of Metal Nanoparticles on Alpha-Cyclodextrin Inclusion Complexes by Magnetron Sputtering}, author = { L. Barrientos-Poblete and P. Allende-Gonz\'{a}lez and C. Orellana and P. Jara}, url = {/brokenurl#<Go to ISI>://WOS:000300180100050}, doi = {10.1016/j.ica.2011.10.032}, issn = {0020-1693}, year = {2012}, date = {2012-01-01}, journal = {Inorganica Chimica Acta}, volume = {380}, pages = {372-377}, publisher = {2011 Elsevier B.V.}, abstract = {An ordered self-assembly of copper, silver and gold nanoparticles onto crystal faces of alpha-cyclodextrin/1-octanethiol and 2 alpha-cyclodextrin/1-octylamine inclusion complexes by means of physical vapor deposition (magnetron sputtering) has been achieved. The preferential deposition on the (001) plane of the supramolecular crystal occurs because the -SH and -NH2 groups from the guest molecules found within the alpha-cyclodextrin protrude into that plane. These functional groups form a two-dimensional hexagonal lattice that interacts with the metal nanoparticles, arranging them in an ordered way.}, keywords = {catalysis, colloids, gold guest host interaction, magnetron metal metal-guest molecules, monolayer, nanoparticles, nanostructures, particles, size, sputtering, stabilization, supramolecular surface}, pubstate = {published}, tppubtype = {article} } An ordered self-assembly of copper, silver and gold nanoparticles onto crystal faces of alpha-cyclodextrin/1-octanethiol and 2 alpha-cyclodextrin/1-octylamine inclusion complexes by means of physical vapor deposition (magnetron sputtering) has been achieved. The preferential deposition on the (001) plane of the supramolecular crystal occurs because the -SH and -NH2 groups from the guest molecules found within the alpha-cyclodextrin protrude into that plane. These functional groups form a two-dimensional hexagonal lattice that interacts with the metal nanoparticles, arranging them in an ordered way. |
Cerda-Monje, A; Aizman, A; Tapia, R A; Chiappe, C; Contreras, R Solvent Effects in Ionic Liquids: Empirical Linear Energy-Density Relationships Artículo de revista Physical Chemistry Chemical Physics, 14 (28), pp. 10041-10049, 2012, ISSN: 1463-9076. Resumen | Enlaces | BibTeX | Etiquetas: ab-initio, catalysis, dielectric-constant, diels-alder electrophilicity field-theory, functional index, models molecular-dynamics, reaction, solvation, static theory @article{RN106, title = {Solvent Effects in Ionic Liquids: Empirical Linear Energy-Density Relationships}, author = { A. Cerda-Monje and A. Aizman and R.A. Tapia and C. Chiappe and R. Contreras}, url = {/brokenurl#<Go to ISI>://WOS:000305890300028}, doi = {10.1039/c2cp40619e}, issn = {1463-9076}, year = {2012}, date = {2012-01-01}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {28}, pages = {10041-10049}, abstract = {Multiparameter linear energy-density relationships to model solvent effects in room temperature ionic liquids (RTILs) are introduced and tested. The model incorporates two solvent dependent and two specific solute-solvent parameters represented by a set of electronic indexes derived from the conceptual density functional theory. The specific solute-solvent interactions are described in terms of the electronic chemical potential for proton migration between the anion or cation and the transition state structure of a specific reaction. These indexes provide a quantitative estimation of the hydrogen bond (HB) acceptor basicity and the hydrogen bond donor acidity of the ionic solvent, respectively. A sound quantitative scale of HB strength is thereby obtained. The solvent dependent contributions are described by the global electrophilicity of the cation and nucleophilicity of the anion forming the ionic liquid. The model is illustrated for the kinetics of cycloaddition of cyclopentadiene towards acrolein. In general, cation HB acidity outweighs the remaining parameters for this reaction.}, keywords = {ab-initio, catalysis, dielectric-constant, diels-alder electrophilicity field-theory, functional index, models molecular-dynamics, reaction, solvation, static theory}, pubstate = {published}, tppubtype = {article} } Multiparameter linear energy-density relationships to model solvent effects in room temperature ionic liquids (RTILs) are introduced and tested. The model incorporates two solvent dependent and two specific solute-solvent parameters represented by a set of electronic indexes derived from the conceptual density functional theory. The specific solute-solvent interactions are described in terms of the electronic chemical potential for proton migration between the anion or cation and the transition state structure of a specific reaction. These indexes provide a quantitative estimation of the hydrogen bond (HB) acceptor basicity and the hydrogen bond donor acidity of the ionic solvent, respectively. A sound quantitative scale of HB strength is thereby obtained. The solvent dependent contributions are described by the global electrophilicity of the cation and nucleophilicity of the anion forming the ionic liquid. The model is illustrated for the kinetics of cycloaddition of cyclopentadiene towards acrolein. In general, cation HB acidity outweighs the remaining parameters for this reaction. |
Publicaciones 2011-2020
