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Updated: Jul 17, 2025

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Proton coupled isomerization in double-hydrogen-bonding-center salicylaldehyde azine
Ye Wang1, Dongdong Wang1, Song Zhang1
1State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
Abstract:
The proton transfer dynamics of Schiff bases are of great importance due to the application potential. The excited state intramolecular proton transfer (ESIPT) of photochromic salicylaldehyde azine (SAA) in solutions was investigated by experimental and computational methods. Two distinguished spectral bands are observed in transient absorption spectra upon the photoexcitation with 400 nm. From the delayed stimulated emission signals, the ESIPT process is determined to be within <200 fs. Subsequently, the photoprotonated products undergo the vibrational relaxation with several picoseconds and the following isomerization with tens of picoseconds. These processes are significantly affected by the polarity of the solvents. The longest component with nanosecond scale can be explained to the relaxation to the enol structure. According to our observations, the SAA molecules with symmetric double-hydrogen-bonding-centers undergo single proton transfer rather than double proton transfer and subsequent intramolecular isomerization.
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