Tesis doctoral inédita leida en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departam... more Tesis doctoral inédita leida en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química. Fecha de lectura: 5-10-199
Han/Hydrogen Bonding and Transfer in the Excited State, 2010
Page 1. 30 Excited-State Double Hydrogen Bonding Induced by Charge Transfer in Isomeric Bifunctio... more Page 1. 30 Excited-State Double Hydrogen Bonding Induced by Charge Transfer in Isomeric Bifunctional Azaaromatic Compounds Dolores Reyman and Cristina Dııaz-Oliva Departamento de Quımica-Fısica Aplicada, Facultad ...
Abstract Fluorescence steady-state and decay measurements of the azaaromatic derivative norharman... more Abstract Fluorescence steady-state and decay measurements of the azaaromatic derivative norharmane were obtained in solvents with different polarities: dichloromethane (DCM) and acetonitrile (ACN), at different temperatures, in the absence and the presence of a donor/acceptor hydrogen bond such as acetic acid. 2D NOESY experiments confirmed that this compound forms a hydrogen-bonding cyclic complex with acetic acid in the ground state. This complex induced a phototautomeric equilibrium, which produced new emission bands at 400 and 500 nm. This tautomeric process was established only in the first excited state via a concerted proton–electron transfer. Indeed, the cyclic complex formed in the ground state evolved to a like-cation upon cooling from room temperature to 225 K, and a new emission band at 450 nm is observed. The fluorescence decay times confirmed these results.
The self-organisation of magnetite nanoparticles (FeNPs) into fractal dendrite-like structures is... more The self-organisation of magnetite nanoparticles (FeNPs) into fractal dendrite-like structures is reported. The fractal alignment was addressed by the diffusion-limited aggregation dynamics of solvent dewetting. Ethylene glycol and folate anion were used as capping agents of the FeNPs. The presence of ethylene glycol is critical for the fractal growth process. X-ray and magnetisation measurements, scanning and transmission electron microscopies, confocal fluorescence and Raman spectroscopies were used to characterise the dendritic structures.
Photoinduced proton transfer reactions of harmane (1-methyl-9H-pyrido[3,4-b]indole) (HAR) in the ... more Photoinduced proton transfer reactions of harmane (1-methyl-9H-pyrido[3,4-b]indole) (HAR) in the presence of a proton donor/acceptor such as dihydrogen phosphate anions in aqueous solution have been studied by stationary and time-resolved fluorescence spectroscopy. The presence of high amounts of dihydrogen phosphate ions modifies the acid/base properties of this alkaloid. Thus, by keeping the pH constant at pH 8.8 and by increasing the amount of NaH(2)PO(4) in the solution, it is possible to reproduce the same spectral profiles as those obtained in high alkaline solutions (pH >12) in the absence of NaH(2)PO(4). Under these conditions, a new fluorescence profile appears at around 520 nm. This result could be related to the results of a recent investigation which suggests that a high intake of phosphates may promote skin tumorigenesis. The presence of β-cyclodextrin (β-CD) avoids the proton transfer reactions in this alkaloid by means the formation of an inclusion complex between β-CD and HAR. The formation of this complex originates a remarkable enhancement of the emission intensity from the neutral form in contrast to the cationic and zwitterionic forms. A new lifetime was obtained at 360 nm (2.5 ns), which was associated with the emission of this inclusion complex. At this wavelength, the fluorescence intensity decay of HAR can be described by a linear combination of two exponentials. From the ratio between the pre-exponential factors, we have obtained a value of K = 501 M for the equilibrium of formation of this complex.
Tesis doctoral inédita leida en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departam... more Tesis doctoral inédita leida en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química. Fecha de lectura: 5-10-199
Han/Hydrogen Bonding and Transfer in the Excited State, 2010
Page 1. 30 Excited-State Double Hydrogen Bonding Induced by Charge Transfer in Isomeric Bifunctio... more Page 1. 30 Excited-State Double Hydrogen Bonding Induced by Charge Transfer in Isomeric Bifunctional Azaaromatic Compounds Dolores Reyman and Cristina Dııaz-Oliva Departamento de Quımica-Fısica Aplicada, Facultad ...
Abstract Fluorescence steady-state and decay measurements of the azaaromatic derivative norharman... more Abstract Fluorescence steady-state and decay measurements of the azaaromatic derivative norharmane were obtained in solvents with different polarities: dichloromethane (DCM) and acetonitrile (ACN), at different temperatures, in the absence and the presence of a donor/acceptor hydrogen bond such as acetic acid. 2D NOESY experiments confirmed that this compound forms a hydrogen-bonding cyclic complex with acetic acid in the ground state. This complex induced a phototautomeric equilibrium, which produced new emission bands at 400 and 500 nm. This tautomeric process was established only in the first excited state via a concerted proton–electron transfer. Indeed, the cyclic complex formed in the ground state evolved to a like-cation upon cooling from room temperature to 225 K, and a new emission band at 450 nm is observed. The fluorescence decay times confirmed these results.
The self-organisation of magnetite nanoparticles (FeNPs) into fractal dendrite-like structures is... more The self-organisation of magnetite nanoparticles (FeNPs) into fractal dendrite-like structures is reported. The fractal alignment was addressed by the diffusion-limited aggregation dynamics of solvent dewetting. Ethylene glycol and folate anion were used as capping agents of the FeNPs. The presence of ethylene glycol is critical for the fractal growth process. X-ray and magnetisation measurements, scanning and transmission electron microscopies, confocal fluorescence and Raman spectroscopies were used to characterise the dendritic structures.
Photoinduced proton transfer reactions of harmane (1-methyl-9H-pyrido[3,4-b]indole) (HAR) in the ... more Photoinduced proton transfer reactions of harmane (1-methyl-9H-pyrido[3,4-b]indole) (HAR) in the presence of a proton donor/acceptor such as dihydrogen phosphate anions in aqueous solution have been studied by stationary and time-resolved fluorescence spectroscopy. The presence of high amounts of dihydrogen phosphate ions modifies the acid/base properties of this alkaloid. Thus, by keeping the pH constant at pH 8.8 and by increasing the amount of NaH(2)PO(4) in the solution, it is possible to reproduce the same spectral profiles as those obtained in high alkaline solutions (pH >12) in the absence of NaH(2)PO(4). Under these conditions, a new fluorescence profile appears at around 520 nm. This result could be related to the results of a recent investigation which suggests that a high intake of phosphates may promote skin tumorigenesis. The presence of β-cyclodextrin (β-CD) avoids the proton transfer reactions in this alkaloid by means the formation of an inclusion complex between β-CD and HAR. The formation of this complex originates a remarkable enhancement of the emission intensity from the neutral form in contrast to the cationic and zwitterionic forms. A new lifetime was obtained at 360 nm (2.5 ns), which was associated with the emission of this inclusion complex. At this wavelength, the fluorescence intensity decay of HAR can be described by a linear combination of two exponentials. From the ratio between the pre-exponential factors, we have obtained a value of K = 501 M for the equilibrium of formation of this complex.
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