Examinando por Autor "Miranda-Rojas, S."
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Ítem Closed-shell d10-d10 in [AuCl(CNR)]n and [AuCl(CO)]n (n = 1, 2; R =-H,-CH3,-Cy) complexes: Quantum chemistry study of their electronic and optical properties(Royal Society of Chemistry, 2022-03) Mendizabal., F.; Miranda-Rojas, S.The electronic structure and spectroscopic properties of [AuCl(CNR)] and [AuCl(CO)] (R =-H,-CH3,-Cy) complexes with d10-d10type interactions were studied at the post-Hartree-Fock (MP2, SCS-MP2, CCSD(T)) and density functional theory levels. It was found that the nature of the intermetal interactions is consistent with the presence of an electrostatic (dipole-dipole) contribution and a dispersion-type interaction. The absorption spectra of these complexes were calculated using the single excitation time-dependent (TD) method at the DFT and SCS-CC2 levels. The calculated values are in agreement with the experimental range, where the absorption and emission energies reproduce the experimental trends, with large Stokes shifts. According to this, intermetallic interactions were found to be mainly responsible for the metal-metal charge transfer (MMCT) electronic transitions among the models studied.Ítem Closed-shell d10–d10 in [AuCl(CNR)]n and [AuCl(CO)]n (n = 1, 2; R = –H, –CH3, –Cy) complexes: quantum chemistry study of their electronic and optical properties(The Royal Society of Chemistry, 2022-03) Mendizabal, F.; Miranda-Rojas, S.The electronic structure and spectroscopic properties of [AuCl(CNR)] and [AuCl(CO)] (R = –H, –CH3, –Cy) complexes with d10–d10 type interactions were studied at the post-Hartree–Fock (MP2, SCS-MP2, CCSD(T)) and density functional theory levels. It was found that the nature of the intermetal interactions is consistent with the presence of an electrostatic (dipole–dipole) contribution and a dispersion-type interaction. The absorption spectra of these complexes were calculated using the single excitation time-dependent (TD) method at the DFT and SCS-CC2 levels. The calculated values are in agreement with the experimental range, where the absorption and emission energies reproduce the experimental trends, with large Stokes shifts. According to this, intermetallic interactions were found to be mainly responsible for the metal–metal charge transfer (MMCT) electronic transitions among the models studied. The [AuCl(CNR)] and [AuCl(CO)] (R = –H, –CH3, –Cy) complexes were modeled and their electronic and optical properties described.Ítem Theoretical exploration of the forces governing the interaction between gold-phthalocyanine and gold surface clusters(Royal Society of Chemistry, 2020) Castro-Latorre, P.; Miranda-Rojas, S.; Mendizabal, F.Here we aim to explore the nature of the forces governing the adsorption of gold-phthalocyanine on gold substrates. For this, we designed computational models of metal-free phthalocyanine and gold-phthalocyanine deposited over a gold metallic surface represented by cluster models of different sizes and geometries. Thereby, we were able to determine the role of the metal center and of the size of the substrate in the interaction process. For this purpose, we worked within the framework provided by density functional theory, were the inclusion of the semi-empirical correction of the dispersion forces of Grimme's group was indispensable. It has been shown that the interaction between molecules and surfaces is ruled by van der Waals attractive forces, which determine the stabilization of the studied systems and their geometric properties. Their contribution was characterized by energy decomposition analysis and through the visualization of the dispersion interactions by means of the NCI methodology. Moreover, calculations of Density of States (DOS) showed that the molecule-surface system displays a metal-organic interface evidenced by changes in their electronic structure, in agreement with a charge transfer process found to take place between the interacting parts.Ítem Unveiling the tartrazine binding mode with ds–DNA by UV–visible spectroscopy, electrochemical, and QM/MM methods(2023-05) Arsenault-Escobar, S.; Fuentes-Galvez, J.F.; Orellana, C.; Bollo, S.; Sierra–Rosales, P.; Miranda-Rojas, S.Here, we studied the interaction between the food colorant tartrazine (TZ) and double stranded DNA (dsDNA), using spectroscopic, electrochemical, and computational methods such as QM/MM combined with TD-DFT. Despite the UV–vis spectroscopy is widely used to study the interaction between molecules, for the case of TZ there are discrepancies in the analyses presented in the literature available, presenting both hyperchromic and hypochromic effects and consequently different rationalizations for their results. Herein we propose the combination of UV–vis experiments with the design of high-level computational models capable of reproducing the experimental behavior to finally define the proper binding mode at the molecular scale together with the rationalization of the experimental optical response due to the complex formation. To complement the UV–vis experiments, we propose the use of electrochemical measurements, to support the results obtained through UV–vis spectroscopy, as it has been successfully used for the determination of interaction modes between small molecules and biomolecules in any condition. Our UV–vis spectroscopy experiments showed only a hypochromic effect of the absorption spectra of TZ after interaction with DNA, indicative of TZ being deeply buried in the DNA structure. The effect of ionic strength in the experimental procedures led to the dissociation of TZ, thus indicating that the interaction mode was groove binding. On the other hand, the electrochemical studies showed an irreversible reduction peak of TZ, which after the interaction with DNA exhibited a positive shift in potential that can be attributed to groove binding. The binding constant for TZ-DNA was calculated as 4.45x104M-1 (UV–vis) and 5.75x104M-1 (electrochemistry), in line with other groove binder azo dyes. Finally, through the QM/MM calculations we found that the minor-groove binding mode interacting in zones rich in adenine and thymine was the model best suited to reproduce the experimental UV–vis response. © 2023 Elsevier B.V.