Activating Photoreaction of Indazole Metastable-State Photoacid through Two-Photon Excitation
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Updated: Oct 25, 2026

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
Published on: February 7, 2022
Ying-Zhong Ma1, Pavithra Liyanage2, Yi Liao2
1Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States.
Abstract:
The photoreaction and functionalities of metastable state photoacids (mPAHs) have been examined almost exclusively through one-photon excitation so far. Here, we report two-photon excited fluorescence measurements on an aqueous solution of a highly water-soluble indazole mPAH. The readily observable fluorescence emission was found to not only follow the anticipated quadratic intensity dependence but also possess a sizeable two-photon absorption cross-section of ∼53 GM. The distinct time-resolved fluorescence decays and emission spectra observed upon one- and two-photon excitation offer indirect evidence for the activation of different isomers and their associated pathways in the respective photoreactions. Our findings pave a promising way of unlocking new functionalities and applications of these mPAHs that are inaccessible to one-photon excitation.
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