Browsing by Author "Aliaga, Margarita E."

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    Linear relationship between emission quantum yield and Stokes shift in 3-styryl aza-coumarin based dyes in the presence of cyclodextrins
    (2023) Alcázar, Jackson; García-Río, Luis; Robles, Agustín I.; Dinamarca-Villarroel, Luis; Fierro, Angélica; Santos, José G.; Aliaga, Margarita E.
    The effect of the cyclodextrins inclusion on the Stokes shifts and emission quantum yield of three 3-styryl aza-coumarin dyes (SACs) was experimentally and theoretically studied. Preliminary results show a relationship between the emission quantum yield and the calculated binding constants. Supramolecular inclusion was supported by changes in the fluorescence spectra, high-resolution mass spectrometry and molecular dynamics studies. 2,6-di-O-methyl-b-cyclodextrin (DM-b-CD) presented higher binding constants than b-cyclodextrin (b-CD), along with up to a 6-fold increase in emission quantum yield for the SACs. Additionally, a linear negative correlation was obtained between the Stokes shift and the emission quantum yield. This linear and empirical relationship was explained by the action of a unique intramolecular rotation and charge transfer phenomenon in the dyes, which was modulated by cyclodextrins, and supported by calculations based on density functional theory.
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    Reactivity of benzohydrazide derivatives towards acetylation reaction. Experimental and theoretical studies
    (2010) Campodónico, Paola; Aliaga, Margarita E.; Santos, José G.; Castro, Enrique A.; Contreras, Renato
    We herein report an experimental and theoretical study on the acetylation reaction of benzohydrazide derivatives towards p-nitrophenyl acetate (NPA). The kinetic data are consistent with a stepwise mechanism with the nucleophilic attack as the rate determining step. From the theoretical analysis it is found that benzohydrazide derivatives establish intramolecular proton rearrangement. The enol form appears as the active species for nucleophilic attack. A reaction mechanism incorporating keto-enol pre-equilibria is proposed. The study is completed with a local reactivity analysis describing the most reactive centers for nucleophilic attack together with a site activation analysis describing inductive substituent effect

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