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ESIPT study in the higher excited states by fluorescent methods

Tomin V., Jaworski R.

Optica Applicata

2010

Vol. 40, nr 3

587--599

Photophysical and photochemical processes in organic molecules are directly related to the singlet electronic S1 state and studied usually without taking into account highest excited states. At the same time the role of high-lying singlet states is not reduced only to processes of intramolecular conversion, they can participate in different intra- and intermolecular processes. Here we consider analytically, in general, how the properties of dually fluorescing molecules are affected in the case where their second fluorescence band is formed as a result of excited state photoreaction and where fluorescence is excited in the range of the S 1 and S n electronic absorption bands. It is shown that, upon excitation of molecular objects via high-lying singlet states, the yield of reaction products can be increased in a number of cases. Then, if fluorescence of initial molecules and their photoproducts is detectable, the probabilities of reactions can be determined via high-lying singlet states. Presented experimental data demonstrate the role of high-lying singlet states of molecules from 3-hydroxyflavone family, in the excited state of which reactions of formation of tautomers as a result of internal proton transfer (ESIPT) can take place. This fact reveals a new opportunity for enlargement yield of photoreactions excited via the Sn states, and in some cases this may be explored practically.

Role of Substituents in Excited State Intramolecular Proton Transfer (ESIPT) Processes

Sepioł J.

Polish Journal of Chemistry

2009

Vol. 83, nr 10

1671-1692

The increasing interest in molecular systems exhibiting ESIPT reaction has triggered – due to their broad field of potential applications – an extensive search for properly substituted compounds with well-tailored properties. This review is based on selected papers dealing with some commonly known ESIPT systems modified by specific substituents. The results of several studies concerning the rate of ultrafast ESIPT reactions in supersonic molecular beams are presented. Articles reporting on phototautomeric fluorescence in solutions illustrated a big role of substituents, which influence the emission quantum yield. Theoretical works pointed to the increasing role of advanced calculations in predicting and understanding the structural, electronic, and spectroscopic properties of diverse ESIPT-capable compounds.