Hydrogen bonding effects on the fluorescence properties of 4′-diethylamino-3-hydroxyflavone in water and water-acetone mixtures
| Autor: | Miklós Kubinyi, Zoltán Szakács, Dávid Mester, Dóra Hessz, Márton Bojtár, Mihály Kállay, István Bitter |
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| Rok vydání: | 2018 |
| Předmět: |
Hydrogen bond
Intermolecular force Quantum yield 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Photochemistry 01 natural sciences Fluorescence Atomic and Molecular Physics and Optics 0104 chemical sciences Analytical Chemistry chemistry.chemical_compound chemistry Excited state Acetone Molecule 0210 nano-technology Hydrate Instrumentation Spectroscopy |
| Zdroj: | Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 203:96-105 |
| ISSN: | 1386-1425 |
| Popis: | The fluorescence properties of 4′-diethylamino-3-hydroxyflavone (FET), a dye probe sensitive to the polarity as well as the hydrogen bonding ability of its environment, have been studied in acetone-water mixtures by measuring spectra and decay curves over the whole composition range and analyzing the results on the basis of theoretical calculations. In acetone, like in most of organic solvents, the dye showed dual fluorescence, due to an excited state intramolecular proton transfer (ESIPT), in which a quasi-equilibrium between the two excited species, N* and T*, was reached. In acetone-water mixtures with lower molar fractions of water, where the water molecules are largely dispersed, only one type of hydrate could be detected, a complex with 1:1 composition, showing only N* emission, but with a high (0.45) fluorescence quantum yield. At higher water concentrations, the interaction of FET with the hydrogen-bonded water clusters resulted in fluorescence quenching. In neat water the fluorescence quantum yield fell to ~0.001. Theoretical calculations on a FET-acetone complex, a FET-water complex and a FET-water-acetone triple complex (the latter as model for the samples with low water concentrations) concluded that ESIPT was energetically favored in all the models, but the E(N*)-E(T*) energy difference for the water complexes was much lower. The kinetic barrier of ESIPT was found greatly higher in the FET-water complex than in the isolated solute. The intermolecular hydrogen bonds in the water complexes became significantly stronger following the excitation, stabilizing the N* form of the hydrated dye. |
| Databáze: | OpenAIRE |
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