Unusually slow proton transfer dynamics of a 3-hydroxychromone dye in protic solvents.
The photophysics of a 3-hydroxychromone dye, 2-(2-furyl)-3-hydroxychromone (FHC) was explored in different types of protic solvents by steady-state and time-resolved fluorescence spectroscopy. FHC exhibits a dual emission, attributable to the excited normal (N*) and tautomer (T*) forms resulting from an excited state intramolecular proton transfer (ESIPT) reaction (N*-->T*). The ESIPT rate decreases with an increase in the hydrogen-bond donating ability of protic solvents. The proton-transfer dynamics is found to be unusually slow ( approximately 10(3) times slower than 3-hydroxyflavone) in strong hydrogen-bond donating solvents like methanol, trifluoroethanol or formamide, where it occurs on a time scale of approximately 100-260 picoseconds. This slow dynamics is likely to be related to the intermolecular solvent-solute H-bonding interactions that compete with the intramolecular H-bond in FHC required for the ESIPT reaction. These data provide a physical background for recent applications of this dye as a fluorescence probe of the microenvironment in biomolecules.
Laboratoire de Biophotonique et Pharmacologie, UMR 7213 du CNRS, Université de Strasbourg, Faculté de Pharmacie, 74 route du Rhin, 67401, Illkirch, France. bkgcranjandas@rediffmail.com
Ranjan
R
Das
Andrey S
AS
Klymchenko
Guy
G
Duportail
Yves
Y
Mély
D000438:Alcohols / Q000737:chemistry; D000577:Amides / Q000737:chemistry; D002867:Chromones / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D007700:Kinetics; D011522:Protons; D012997:Solvents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
C479534:3-hydroxychromone; D000438:Alcohols; D000577:Amides; D002867:Chromones; D004396:Coloring Agents; D011522:Protons; D012997:Solvents