Journal
JOURNAL OF LUMINESCENCE
Volume 129, Issue 4, Pages 382-388Publisher
ELSEVIER
DOI: 10.1016/j.jlumin.2008.11.006
Keywords
2,3-diazabicyclo[2.2.2]oct-2-ene; Fluorescence quenching; Uracil; Electron transfer; Deuterium isotope effect
Categories
Funding
- CSIR
- [SP/S1/H-41/2001]
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The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by a series of uracils has been studied in water and acetonitrile solvents using steady-state and time-resolved fluorescence techniques. The steady-state fluorescence quenching technique has been performed in three different pHs (i.e. 4, 8 and 12). The bimolecular quenching rate constant (k(q)) increases with increase in pH of uracils. In acidic pH, a pure hydrogen atom abstraction is proposed as the quenching mechanism. This is supported by a pronounced solvent deuterium isotope effect. Electron transfer from the anionic form of uracil to the excited state of DBO is proposed as a mechanism for quenching in basic pH on the basis of highly exergonic thermodynamics obtained from the Rehm-Weller equation. The variation of k(q) is explained on the basis of the electronic effect of substitution in uracils as well. (C) 2008 Elsevier B.V. All rights reserved.
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