engleski

Excited State Intramolecular Proton Transfer From Nitrogen To Carbon Atom In Aminobiphenyls

Excited-state intramolecular proton transfer (ESIPT) is a fundamental photochemical reaction that has been intensively investigated due to numerous applications in sensing technologies and material science.[1] ESIPT takes place in molecules bearing proton donor and acceptor groups in close proximity, whose acidity and basicity are enhanced upon excitation. Furthermore, example of ESIPT between the phenolic OH and the adjacent carbon atom have been well documented. However, examples where amino functional group acts as a photoacid are scarce. Here we report on the investigation of ESIPT reactivity in o-, m- and p- aminobiphenyl derivatives. The process was investigated by irradiations in D2O-CH3CN whereupon the regiospecific deuterium incorporation took place and indirectly pointed to the ESIPT reaction mechanism. Properties of the excited states leading to the ESIPT were investigated by steady-state and time-resolved fluorescence, and we determined the pKa values of the molecules in the ground and the first singlet excited state by UV-vis and fluorescence titrations. To corroborate the experimental findings, the computations have been performed using the Algebraic Diagrammatic Construction to second order (ADC(2) method, [3] which completely unraveled the reaction mechanism and observed ESIPT photochemical pathways.

Excited State Intramolecular Proton transfer (ESPIT) ; Aminobiphenyls ; Photochemistry

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