Photophysical behavior of mono- and bis(2′-hydroxyphenyl)-6-(4′-diphenylaminophenyl)pyrimidines: Interplay of ESIPT, ICT, and vibrational nonradiative decay
Abstract
Mono- and bis(2'-hydroxyphenyl)-6-(4'-diphenylaminophenyl)pyrimidines were investigated to elucidate the interplay between excited-state intramolecular proton transfer (ESIPT), intramolecular charge transfer (ICT), and vibrational non-radiative decay processes governing their photophysical properties. Under neutral conditions, all compounds exhibit extremely low fluorescence quantum yields. Time-dependent density functional theory (TD-DFT) calculations indicate that proton transfer is energetically accessible in the excited state; however, the absence of a significant decrease in oscillator strength upon enol-keto conversion demonstrates that ESIPT does not lead to a dark excited state and is not the dominant deactivation pathway. Analysis of vibrational reorganization energies and Huang-Rhys factors reveals strong coupling between the electronic transition and low-frequency vibrational modes, suggesting that vibrationally assisted internal conversion plays a major role in fluorescence quenching. Upon protonation of the pyrimidine nitrogen atoms, marked bathochromic shifts are observed, accompanied by suppression of the ESIPT pathway and enhancement of ICT character. Nevertheless, fluorescence remains weak in polar media, consistent with efficient non-radiative decay from stabilized charge-transfer states, and increases in less polar solvents. Overall, these results highlight the complex interplay between ESIPT, ICT, and vibrational coupling in these pyrimidine-based chromophores, with vibrationally assisted non-radiative decay emerging as a dominant contribution to their excited-state deactivation.
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BibTeX
@article{diguet2026photophysical,
title = {{Photophysical behavior of mono- and bis(2′-hydroxyphenyl)-6-(4′-diphenylaminophenyl)pyrimidines: Interplay of ESIPT, ICT, and vibrational nonradiative decay}},
author = {Clément Diguet and Julián Rodríguez-López and M. Paz Fernández-Liencres and Amparo Navarro and Sébastien Gauthier and Françoise Robin-Le Guen and Sylvain Achelle},
journal = {Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy [1994-...]},
year = {2026},
month = jun,
doi = {10.1016/j.saa.2026.128334},
url = {https://hal.science/hal-05742196v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Photophysical behavior of mono- and bis(2′-hydroxyphenyl)-6-(4′-diphenylaminophenyl)pyrimidines: Interplay of ESIPT, ICT, and vibrational nonradiative decay
AU - Clément Diguet
AU - Julián Rodríguez-López
AU - M. Paz Fernández-Liencres
AU - Amparo Navarro
AU - Sébastien Gauthier
AU - Françoise Robin-Le Guen
AU - Sylvain Achelle
PY - 2026
DA - 2026/06/29
JO - Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy [1994-...]
DO - 10.1016/j.saa.2026.128334
UR - https://hal.science/hal-05742196v1
AB - Mono- and bis(2'-hydroxyphenyl)-6-(4'-diphenylaminophenyl)pyrimidines were investigated to elucidate the interplay between excited-state intramolecular proton transfer (ESIPT), intramolecular charge transfer (ICT), and vibrational non-radiative decay processes governing their photophysical properties. Under neutral conditions, all compounds exhibit extremely low fluorescence quantum yields. Time-dependent density functional theory (TD-DFT) calculations indicate that proton transfer is energetically accessible in the excited state; however, the absence of a significant decrease in oscillator strength upon enol-keto conversion demonstrates that ESIPT does not lead to a dark excited state and is not the dominant deactivation pathway. Analysis of vibrational reorganization energies and Huang-Rhys factors reveals strong coupling between the electronic transition and low-frequency vibrational modes, suggesting that vibrationally assisted internal conversion plays a major role in fluorescence quenching. Upon protonation of the pyrimidine nitrogen atoms, marked bathochromic shifts are observed, accompanied by suppression of the ESIPT pathway and enhancement of ICT character. Nevertheless, fluorescence remains weak in polar media, consistent with efficient non-radiative decay from stabilized charge-transfer states, and increases in less polar solvents. Overall, these results highlight the complex interplay between ESIPT, ICT, and vibrational coupling in these pyrimidine-based chromophores, with vibrationally assisted non-radiative decay emerging as a dominant contribution to their excited-state deactivation.
SN - 1386-1425
SN - 1873-3557
ER -