Proton-transfer reactions in the excited state of phenanthrylamines by nanosecond spectroscopy and fluorimetry

Abstract
Proton-transfer reactions in the excited singlet state of phenanthrylamines at 300 K have been studied by means of nanosecond time-resolved spectroscopy and fluorimetry. On the basis of dynamic analyses involving proton-induced fluorescence quenching, the proton dissociation (k1) and association (k2) rate constants and the acidity constants pK* a in the excited singlet state of phenanthrylamines were determined. The pK* a values are discussed theoretically by taking account of their electronic structures. An empirical equation to estimate approximately the correct pK* a values of aromatic amines using data from Stokes shifts and (pK* a)FC values (determined by the Förster cycle) is proposed. Isotope effects on the rate constants and pK* a values have also been examined.

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