Proton transfer dynamics in a polar nanodroplet: ESIPT of 4'-n,n-dimethylamino-3-hydroxyflavone in AOT/alkane/water reverse micelles
| Autor: | Debabrata Mandal, Deborin Ghosh, Shaikh Batuta, Naznin Ara Begum |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Chemistry
Intermolecular force 3-Hydroxyflavone Biophysics Solvation Ionic bonding 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics Photochemistry 01 natural sciences Biochemistry Tautomer Enol Micelle Atomic and Molecular Physics and Optics 0104 chemical sciences chemistry.chemical_compound Excited state 0210 nano-technology |
| Zdroj: | Journal of Luminescence. 184:64-73 |
| ISSN: | 0022-2313 |
| Popis: | The excited state intramolecular proton transfer (ESIPT) of the well-known fluorophore 4'-N,N-Dimethylamino-3-hydroxyflavone (DMA3HF) was studied in AOT/n-heptane/water reverse micelle solutions. For DMA3HF molecules located inside the AOT encapsulated polar nanodroplets, ESIPT from excited enol (E*) to tautomer (T*) forms was markedly inhibited, yielding time-constants of ≥100 ps, and followed the same trend as solvent relaxation when the ratio W= [H 2 O]/[AOT] was varied. At W=0, the DMA3HF molecules were attached to the ionic AOT headgroups via strong intermolecular H-bonding, which hindered ESIPT. Addition of water changes the situation radically: water molecules form stronger H-bonds with AOT headgroups, displacing the DMA3HF, which are instead engaged in intermolecular H-bonded complexes of the type [DMA3HF···water]. ESIPT of these complex-bound fluorophores involves substantial rearrangement of H-bonding, and is coupled to solvation dynamics. With increasing W-value, solvation becomes faster, and so does ESIPT, reducing the yield of E* species. At the same time, the local environment within the nanodroplets become more more polar with gradual accumulation of water, which causes a monotonic red-shift of the E* emission peak. |
| Databáze: | OpenAIRE |
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