Chemical control of Hemithioindigo-photoisomerization – Substituent-effects on different molecular parts

Making Fast Photoswitches Faster—Using Hammett Analysis to Understand the Limit of Donor–Acceptor Approaches for Faster Hemithioindigo Photoswitches

“…b) Correlation between the σ + constant and the measured excited‐state lifetimes of the E isomer ( τ E , ✶), and E / Z photoisomerization lifetimes (τ E / Z , ♦) calculated from the measured excited‐state lifetimes ( τ E ) and the quantum yield of E / Z photoisomerization. The data for HTI 2 were taken from the literature 18b…”

Hemithioindigo—an emerging photoswitch

“…[38] The photoisomerization of unsubstituted HTI 1 is a very fast process, and takes about 38 ps with a quantum yield of 12% (in CH 2 Cl 2 as solvent). [9,39] The reverse E/Z photoisomerization is initiated by light with longer wavelengths (typically >500 nm) and proceeds faster (23 ps) but with lower quantum yield (5%). [9] This is due to another radiationless deexcitation channel of the E isomer, which does not lead to isomerization.…”

“…time-resolved absorption, [40] fluorescence, and IR or Raman spectroscopy, 3, 5b-e, 5g which allow to investigate fast photochemical reactions on very short (fs or ps) time scales. Seminal studies of the ultrafast behavior of HTIs upon photoexcitation were carried out by the groups of Zinth and Rück-Braun [39,41] and a thorough theoretical description of the excited state of unsubstituted HTI 1 by de Vivie-Riedle and coworkers. [42] Earlier theoretical descriptions have been given by the groups of Ganguly [43] and Plötner.…”

“…Especially the para-position of the sulfur atom is sensitive, as donor substituents in this position lead to a notable decrease in photoisomerization speed. [39] A mechanistic explanation for this behavior has yet to be given.…”

Bistable Photoswitching of Hemithioindigo with Green and Red Light: Entry Point to Advanced Molecular Digital Information Processing

“…The quantum yields of photoisomerization are found to be between 5 and 52 % (the quantum yields for both switching directions are given in the Supporting Information for all HTIs 1 to 6 ). The photoswitching properties of HTIs 1 to 3 have been thoroughly analyzed previously and served as the starting point for optimization. HTIs 1 to 3 bear substituents with increasing electron donor capacity in the para ‐position of the stilbene fragment, which leads to a strong redshift of the absorption (e.g.…”