Abstract
Abstract The fluorescence quenching of water-soluble and amphiphilic anthracene sulphonates (monosulphonates and disulphonates) by I − , N 3 − , Br − and Cl − was studied. The rate constants for quenching depend on the ionic strength of the solution, and at μ = 0 they are observed to be a function of the redox potentials of the quenchers, except for the azide iron. The free energy Δ G ° of the quenching reaction was calculated for anthracene-1-sulphonate and anthracene-1,5-disulphonate from the redox potentials of the fluorescers and quenchers. A linear correlation is observed in the endoergic region of Δ G ° (for Br − and Cl − , including I − in the exoergic region, suggesting an electron transfer mechanism. The slope is only about 2 eV −1 , compared with the ideal value of 17 eV −1 . From the temperature dependence of the quenching the thermodynamic parameters Δ H ≠ , Δ S ≠ and Δ G ≠ were evaluated for I − , N 3 − and Br − , and the results indicate that the entropy of activation Δ S ≠ plays a definite role. N 3 − does not follow an isokinetic plot.
Published Version
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