Rapid Intersystem Crossing Induced by Ultrafast Excited-State Intramolecular Proton Transfer in 3-Mercaptopyran-4-one

Abstract

Investigation into the photoinduced processes of 3-mercaptopyran-4-one is carried out using trajectory-based surface hopping simulations. Excitation into the near-degenerate higher singlet excited states reveals rapid internal conversion (IC) into S 1 on a sub-50 fs timescale. Excited-state intramolecular proton transfer (ESIPT) also takes place simultaneously with IC. We observe that following tautomerization, the molecule has multiple relaxation pathways. A channel exists for it to nonradiatively decay into the tautomer ground-state or undergo rapid intersystem crossing (ISC) into the close-lying higher triplet state, which ultimately decays into T 1 . The simulations show that ISC is significantly enhanced after ESIPT, which is studied by tracking the changes in energy gaps and associated spin−orbit coupling elements.

ESIPT-induced spin–orbit coupling enhancement leads to tautomer fluorescence quenching of the 10-HHBF molecule

“…Based on the analysis above, it is concluded that the ESIPT process induces the SOC enhancement characteristic in 10-HHBF. The interesting phenomenon is consistent with the recent computational study reported by Vennapusa et al 35 Thus, the characteristic of the ESIPT-induced SOC enhancement causes the efficient ISC process from the S 1 Keto* to T 3 state, which in turn quenches the tautomer fluorescence for 10-HHBF. Besides, based on the Keto* form, we scanned the PECs of S 0 , S 1 and T 3 states for the 10-HHBF along the rotation coordinate (Fig.…”

Fluorescence quenching of deprotonated phenylurea through twisting motion induced by an electron-donating substituent group

“…Excited-state proton transfer is one of the most important reactions in photochemistry and has been investigated extensively using various experimental and theoretical methods owing to its potential applications in fluorescent sensors, bioimaging technologies, and OLEDs. [1][2][3][4][5][6][7][8] Excited-state proton transfer reactions can be classified as excited-state intramolecular proton transfer (ESIPT) [9][10][11][12][13][14][15][16] and excited-state intermolecular proton transfer (ESPT). [17][18][19][20][21][22][23] The dynamic mechanism of ESIPT reaction is relatively perspicuous and can be usually described as a four-step cyclic phototautomerization process: excitation of the compound, proton transfer (PT) in the excited state, deexcitation to the ground state, and reversed PT in the ground state.…”