Multivariate Analysis of the Fluorescence Decay of 3-Hydroxyflavone in Various Solvents

DeSario, Douglas Y.
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University of Delaware
The photokinetic parameters of the fluorescence decay of 3-hydroxyflavone were determined in six solvents, which were chosen for their widely differing polarities, dielectric constants, and hydrogen bonding capabilities. This was accomplished by the separation of three-dimensional time-resolved emission decay matrices through multivariate analysis. Particular attention was paid to the dual fluorescence of the main conformers of 3-hydroxyflavone – the normal and the tautomer – which forms the basis of the use of this molecule, and its derivatives, as fluorescent probes of solvent properties. The normal fluorescence was found to occur strongly only in solvents with the capability to hydrogen bond with the 3-hydroxyl group, thereby slowing the Excited State Intramolecular Proton Transfer (ESIPT) reaction that, unhindered, partially relaxes the normal excited state to the tautomer excited state. The photokinetic parameters that were calculated were the average excited state lifetimes, their initial intensities, and matrices of rate constants that quantified both the decay of each conformer of 3-hydroxyflavone in the excited state, and also the influences of each conformer on the others’ fluorescence. These parameters, as well as the λmax of the individual conformers, compared favorably to previous studies of this molecule.