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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.

Anomalous broadening of DMABN electronic spectra in solutions

Tomin V, Hubisz K

Optica Applicata

2006

Vol. 36, nr 4

s. 475--481

The results of spectral broadening study of electronic bands of an archetype molecule with intramolecular charge transfer in the excited state, n-dimethylaminobenzonithrile (DMABN), in polar solvents are discussed. The broadening is anomalously large, it amounts to 8000 cm–1, and manifests itself in both luminescence and excitation spectra. The explanation of the results obtained is based on treating a solution as a set of chemically identical solvates with solute in the centre, which have different energies of the pure electronic transitions. The inhomogeneity is likely to arise due to both the intermolecular effect of luminophor environment on its spectra in polar solvents and the existence of various conformers of DMABN.