engleski

Excited-state intramolecular proton transfer from nitrogen to a C-atom of adjacent aromatic substituent

Excited-state intramolecular proton transfer (ESIPT) is a fundamentally important process[1]. The ESIPT takes place in molecules bearing proton donor and acceptor groups in close proximity, whose acidity and basicity are enhanced upon excitation. The most common acidic group is OH, and the ESIPT from this group is possible to various basic sites, including C-atoms of adjacent aromatic substituents. The most efficient ESIPT from the OH to a C-atom was observed for 2-phenyl-1-naphthol [2, 3]. In continuation of the aforementioned research here we report on the ESIPT in analogous amino compounds (Figure 1.). The ESIPT has been investigated by irradiation of these compounds in the CH3CN-D2O system, whereupon D-incorporation takes place. The dependence on the water content as well as changes of the pH on ESIPT were investigated. Properties of the excited states leading to the ESIPT were probed by steady-state and time-resolved fluorescence. 2-(2-naphthyl)aniline proved to be the most reactive compound and its pKa values were determined in S0 and S1 by fluorescence titrations. For the detection of reactive intermediates, LFP experiments were performed. To confirm the presumed reaction mechanism, calculations were conducted in the ground state with MP2/cc-pVDZ and in the excited state with ADC(2)/cc-pVDZ.

ESPIT ; LFP experiments ; Proton Donor ; Proton Acceptor

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