Hannover 2020 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 4: Electronic Spectroscopy I

MO 4.9: Vortrag

Montag, 9. März 2020, 16:15–16:30, f142

Excited state lifetimes of indole, 3-,4-, and 5-cyanoindole and pKa values of cyanoindoles in the ground and first excited state. — •Hilda Lartian, Marie-Luise Hebestreit, Carolin Borbeck, and Michael Schmitt — Institute for Physical Chemistry I, Heinrich-Heine-University, Düsseldorf

In this contribution the excited state lifetimes of indole, 3-cyanoindole (d1), 4-cyanoindole (d1) and 5-cyanoindole in D2O and ethylacetate solution, obtained from time correlated single photon counting (TCSPC), are presented and compared to excited state lifetimes in the gas phase. The excited state lifetime of 4-cyanoindole (d1) in ethylacetate and D2O solution is longer than of bare indole and the other cyanoindoles. 4-cyanoindole (d1) shows a different behavior in the gas phase and has a shorter lifetime than 3-cyanoindole (d1), while 3-cyanoindol has a shorter excited state lifetime than 4-cyanoindole. The different behavior of 3-, 4-, and 5-cyanoindole is discussed on the basis of the different electronic nature of the electronically excited singlet states. Furthermore the pKa values of cyanoindoles in the ground and excited state have been measured using UV/Vis absorption spectroscopy. 2- and 3-cyanoindole have lower ground state pKa values (<13) than the other cyanoindoles (>14). Only for 4- and 7-cyanoindole a significant shift in pKa upon excitation can be detected which might be due to low fluorescence lifetimes of the other cyanoindoles.

[1] Schneider et al, Phys. Chem. Chem. Phys., 2018, 20, 23441

[2] Hebestreit et al, Phys. Chem. Chem. Phys., 2019, 21, 14766

[3] Wilke et al, Chem. Phys. Chem., 2016, 17, 2736.

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