Correlation between Excited-State Intramolecular Proton-Transfer
and Singlet-Oxygen Quenching Activities in 1‑(Acylamino)anthraquinones
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Abstract
Excited-state
intramolecular proton-transfer (ESIPT) and singlet-oxygen
(<sup>1</sup>O<sub>2</sub>) quenching activities of intramolecularly
hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means
of static and laser spectroscopies. The ESIPT shows a substituent
effect, which can be explained in terms of the nodal-plane model.
The ESIPT activity positively and linearly correlates with their <sup>1</sup>O<sub>2</sub> quenching activity. The reason for this correlation
can be understood by considering ESIPT-induced distortion of their
ground-state potential surface and their encounter complex formation
with <sup>1</sup>O<sub>2</sub>. Intramolecularly hydrogen-bonded hydroxyanthraquinones
found in aloe also show a similar positive and linear correlation,
which can be understood in the same way
