Naslov
Photodehydration mechanisms of quinone methide formation from 2-naphthol derivatives

Autori
Forjan, Mateo ; Vdović, Silvije ; Šekutor, Marina ; Škalamera, Đani ; Kabaciński, Piotr ; Cerullo, Giullio

Izvornik
Journal of photochemistry and photobiology. A, Chemistry (1010-6030) 433 (2022); 114171, 10

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

Ključne riječi
femtosecond transient absorption ; naphthols ; quinone methides ; conical intersection ; photodehydration

Sažetak
Photogeneration of quinone methides (QM) from 3- hydroxymethyl-2-naphthol (1) and 3-(2-hydroxy-2- adamantyl)-2-naphthol (2) was investigated using femtosecond and nanosecond transient absorption spectroscopy and supported with theoretical analysis of possible reaction pathways. Our results indicate that adamantylnaphthol 2 after UV excitation undergoes a non-adiabatic excited state intramolecular proton transfer coupled with dehydration via a conical intersection, delivering the corresponding QM (S0) within 1 ns. Surprisingly, in naphthol 1 on femtosecond time scale only formation of radical cation and solvated electrons was observed where the photoionization is a competing process not connected to the photochemical reaction of QM formation. Radical cations decay fast (45 ps) due to the back electron transfer. By quenching with ascorbate we identified phenoxyl radicals as a QM precursor, which are formed in a slower H-transfer reaction taking place on nanosecond time scale. Our combined experimental and theoretical investigation point to a polycyclic substituent effect, which profoundly changes the photochemical reaction pathway.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija, Interdisciplinarne prirodne znanosti

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