Study of Two-Photon induced excited state absorption of Three-Branched triphenylamine Derivatives: Cooperative and Anti-Cooperative effect of electron transition in the excited state

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2025-02, Vol.459, p.116078, Article 116078
• Main Authors: Jia, Jidong, Zhang, Tianwei, Lu, YinLin, Xu, JingYuan, Wu, Xingzhi, Song, Yinglin
• Format: Article
• Language: English
• Subjects: Cooperative effect; Multi-branched triphenylamine derivatives; Nonlinear optics; Transient dynamics; Two-photon induced excited state absorption
• ISSN: 1010-6030
• DOI: 10.1016/j.jphotochem.2024.116078

[Display omitted] •Modulation of nonlinear absorption of multibranched molecule by electron transition.•Intersystem crossing in multibranched molecules enables long-lived excited state absorption.•Natural transition orbitals show the effect of dipole moment on electron transition.•Enhancement of two-photon induced excited state absorption by cooperative effect. For multi-branched molecules, intramolecular cooperative effect can significantly enhance the molecular nonlinear optical absorption. Three triphenylamine-cored compounds (N1, N2 and N3) with three branches are synthesized to study the cooperative and anti-cooperative effect of electron transition in the excited state on two-photon absorption (TPA) and excited state absorption (ESA). Molecular polarization of these multi-branched triphenylamine derivatives is regulated by changing the molecular symmetry and the planarity of peripheral branches, to regulate their charge distribution and electron transition characteristics in the excited state. Here, we show that due to electronic coupling and interaction between certain branches, the asymmetric distribution of electron clouds in the excited states of these multi-branched molecules will lead to an enhancement of their TPA and ESA cross-sections, which is known as the cooperative effect of electron transitions. On the contrary, electronic coupling and interaction among all branches will lead to a highly symmetric distribution of electron clouds in the excited states of these multi-branched molecules, which will cause anti-cooperative effects and result in significant attenuation of TPA and ESA cross-sections.