The role of branching in the ultrafast dynamics and two-photon absorption of two pyrimidine push-pull molecules.

Authors

Alexandros Katsidas, Michaela Fecková, Filip Bureš, Sylvain Achelle, Mihalis Fakis

Published in

Physical chemistry chemical physics : PCCP. May 21, 2025. Epub May 21, 2025.

Abstract

The dynamics and two-photon absorption (2PA) properties of two pyrimidine chromophores are studied using femtosecond time-resolved fluorescence and two-photon excited fluorescence techniques. The pyrimidine is used as an electron withdrawing group and is substituted at the C2 position with a phenylacridan fragment, while diphenylaministyryl donor moieties are appended at positions C4/6 to afford the pseudo-dipolar and pseudo-quadrupolar molecules 1 and 2, respectively. Chromophore 2 shows more efficient fluorescence emission, while 1 exhibits larger Stokes shifts. Their decay pathways are discussed through an emission from a Franck-Condon charge transfer (FC-CT) and a relaxed charge transfer (R-CT) state. Ultrafast dynamics in tetrahydrofuran show population of the R-CT state for 1 that is faster than solvation, while for 2, due to its pseudo-quadrupolar nature, R-CT population is slower and occurs from the solvated FC-CT state. Finally, molecule 2 shows better 2PA properties with cross sections reaching 560 GM at 820 nm.

PMID:
40396205
Bibliographic data and abstract were imported from PubMed on 21 May 2025.

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