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Updated: May 13, 2026

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
Published on: February 7, 2022
Photoisomerization of saccharin
L Duarte1, I Reva, M L S Cristiano
1Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal.
Abstract:
Most known applications of saccharin and saccharyl derivatives and their potential for new uses rely on the thermal and photochemical stability of the saccharyl system. Here, we show that saccharin undergoes structural rearrangement when subjected to a narrow-band ultraviolet irradiation. Monomeric saccharin was isolated in low-temperature argon matrices and its photochemistry was characterized by means of infrared spectroscopy and DFT calculations. Among several DFT methods used, the O3LYP/6-311++G(3df,3pd) level gave the best match with the experimental spectra. Irradiation of matrix-isolated saccharin, with a narrow-band source (290 nm), generates a so far unknown isomer that we call iso-saccharin. The structures of the conjugate bases of saccharin and iso-saccharin were also computed theoretically. Their free energies and dipole moments suggest that both anions may be relevant in systems where saccharin participates, as is the case of the recently proposed saccharin-based ionic liquids.
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