Naslov
Photophysics of push-pull distyryl furans, thiophenes and pyridines by fast and ultrafast techniques

Autori
Carlotti, Benedetta ; Kikaš, Ilijana ; Škorić, Irena ; Spalletti, Anna ; Elisei, Fausto

Izvornik
ChemPhysChem (1439-4235) 14 (2013), 5; 970-981

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
distyryl derivatives ; furan ; thiophene ; pyridine ; photophysics

Sažetak
Time−resolved transient absorption and fluorescence spectroscopies with nano− and femto −second time resolution were used to investigate in detail the deactivation pathways of the excited states of distyryl furan, thiophene and pyridine derivatives in organic solvents. The rate constant of the main decay processes (fluorescence, singlet −triplet intersystem crossing, isomerization and internal conversion) are strongly affected by the nature (locally excited, LE, or charge transfer, CT) and selective position of the lowest excited singlet states. In particular, the heteroaromatic central ring enhances significantly the intramolecular charge transfer process which is operative even in a non−polar solvent. Both the thienyl and pyridyl moieties enhance the S1 → T1 rate with respect to the furyl one. This is due to the heavy atom effect (thienyl −compounds) and to the 1(π, π)* → 3(n, π)* transition (pyridyl −compounds) which enhance the spin−orbit coupling. Moreover, also the solvent polarity plays a significant role on the photophysical properties of these push−pull compounds: in fact a particularly fast 1LE* → 1CT* process was found for dimethylamine−derivatives in the more polar solvents (time constant, τ ≤ 400 fs) while it takes place in tenths of ps in non−polar solvents. It was also shown that the CT character of the lowest excited singlet state decreased by replacing the dimethylamine side group by a methoxy one. This latter causes a decrease of the emissive decay and an enhancecement of the triplet state formation. The photoisomerization mechanism (singlet/triplet) is also discussed.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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