Ultrafast Charge Relocation Dynamics in Enol–Keto Tautomerization Monitored with a Local Soft-X-ray Probe

Abstract

Proton-coupled electron transfer (PCET) is the underlying mechanism governing important reactions ranging from water splitting in photosynthesis to oxygen reduction in hydrogen fuel cells. The interplay of proton and electronic charge distribution motions can vary from sequential to concerted schemes, with elementary steps occurring on ultrafast time scales. We demonstrate with a simulation study that femtosecond soft-X-ray spectroscopy provides key insights into the PCET mechanism of a photoinduced intramolecular enol* → keto* tautomerization reaction. A full quantum treatment of the electronic and nuclear dynamics of 2-(2′-hydroxyphenyl)benzothiazole upon electronic excitation reveals how spectral signatures of local excitations from core to frontier orbitals display the distinctly different stages of charge relocation for the H atom, donating, and accepting sites. Our findings indicate that ultraviolet/X-ray pump-probe spectroscopy provides a unique way to probe ultrafast electronic structure rearrangements in photoinduced chemical reactions essential to understanding the mechanism of PCET.

Green synthesis of UV absorber (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol by microwave method

“…The use of Schiff bases as the organic UV absorbers is well demonstrated in numerous reports in the literature [7][8][9][10]. The UV protection mechanism of Schiff base linked to their enol -keto transformation during UV absorption [11][12].…”