Much attention has been directed, from both of experimental and theoretical viewpoints, towards excited-state intramolecular proton transfer (ESIPT) and singlet-oxygen (1O2, 1?g state) quenching. Both of them play key roles in many photochemical and photobiological processes, and are associated with significant applications in several fields.In this study, we have studied the ESIPT and 1O2 quenching activities of intramolecularly hydrogen-bonded anthraquinone derivatives by means of laser spectroscopy. As shown in the figure given below, the ESIPT activity in these molecules linearly correlates with their 1O2 quenching activity, and the molecules susceptible to ESIPT have high 1O2-quenching function.  Here, AAAQ etc. refer to abbreviated names of the intramolecularly hydrogen-bonded anthraquinone derivatives used in this study. kQ denotes the second-order rate-constant of 1O2 quenching, and FLWE and FSWE stand for fluorescence quantum yields of the proton-transferred and normal forms, respectively.The ESIPT activity can be explained in terms of the nodal-plane model,1 which is a qualitative theoretical model but allows us to recognize the important features of ESIPT immediately. The linear relationship between the ESIPT and 1O2 quenching activities can be interpreted on the basis of ESIPT-induced distortion of ground-state potential surfaces in encounter complexes with 1O2.1. Nagaoka, S. et al. J. Phys. Chem. 1988 , 92, 166-171.

Correlation between excited-state intramolecular proton-transfer and singlet-oxygen quenching activity in intramolecularly hydrogen-bonded anthraquinone derivatives

248th National Meeting (2014)

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