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Title: | Dramatic Pressure-Dependent Quenching Effects in Supercritical CO2 Assessed by the Fluorescence of 4‘-Dimethylamino-3-hydroxyflavone. Thermodynamic versus Kinetics Control of Excited-State Intramolecular Proton Transfer | Authors: | Barroso, Mónica Chattopadhyay, Nitin Klymchenko, Andrey S. Demchenko, Alexander P. Arnaut, Luís G. Formosinho, Sebastião J. |
Issue Date: | 21-Dec-2006 | Publisher: | American Chemical Society | Citation: | The Journal of Physical Chemistry A. 110:50 (2006) 13419-13424 | Abstract: | Steady-state fluorescence of 4‘-dimethylamino-3-hydroxyflavone (DMA3HF) was observed in supercritical carbon dioxide (scCO2). Excited-state intramolecular proton transfer (ESIPT) occurs resulting in two well-separated emission bands corresponding to the normal and tautomer forms. As the scCO2 density exceeds 0.7 g/mL, the relative intensity of the two bands tends to a constant value, comparable to that observed for organic solvents with ET(30) = 33.0 ± 0.5 kcal/mol, such as toluene and di-n-butyl ether. At lower densities, the substantial decrease of the total fluorescence intensity (a 600-fold decrease as the pressure decreases from 100 to 80 bar) is accompanied by an even more accentuated decrease of the tautomer fluorescence. This can be explained by a shift in the equilibrium between normal and tautomer forms, concomitant with a more efficient quenching of the less solvated fluorophore, that may change the thermodynamic control of the relative population of the two emissive species to a kinetic control. | URI: | https://hdl.handle.net/10316/10640 | ISSN: | 1089-5639 | DOI: | 10.1021/jp0643606 | Rights: | openAccess |
Appears in Collections: | FCTUC Química - Artigos em Revistas Internacionais |
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Dramatic Pressure-Dependent Quenching Effects in Supercritical.pdf | 99.5 kB | Adobe PDF | View/Open |
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