Oxidized Hemithioindigo Photoswitches—Influence of Oxidation State on (Photo)physical and Photochemical Properties

Abstract

The photophysical and photochemical properties of sulfoxide and sulfone derivatives of hemithioindigo photoswitches are scrutinized and compared to the unoxidized parent chromophores. Oxidation results in significantly blue‐shifted absorptions and mostly reduction of photochromism while thermal stabilities of individual isomers remain largely unaltered. Effective photoswitching takes place at shorter wavelengths compared to parent hemithioindigos and high isomeric yields can be obtained reversibly in the respective photostationary states. Reversible solid‐state photoswitching is observed for a twisted sulfone derivative accompanied by visible color changes. These results establish oxidized hemithioindigo photoswitches as promising and versatile tools for robust light‐control of molecular behavior for a wide range of applications.

A cross-conjugation approach for high-performance diaryl-hemithioindigo photoswitches

“…[23][24][25][26] From the different variants such as indigo, [27][28][29] indirubin, 30 or thioindigo, 31 hemiindigo, 32,33 and especially hemithioindigo 25 (HTI, see also ref. [34][35][36] for some recent HTI-photoswitch examples) stand out as especially versatile core structures. HTI-based photoswitches consist of a central isomerizable double bond, which connects a benzothiophenone (a half-or hemithioindigo) fragment to one aromatic residue typically termed the stilbene fragment (Fig.…”

Recent Advances in Photoswitchable Fluorescent and Colorimetric Probes

“…The Z/E isomerization can be triggered and reversed by specific light wavelengths or thermally in the dark, with the isomerization dynamics also sensitive to the surrounding chemical environment. Hemithioindigo compounds are utilized across diverse applications such as optical data storage, smart materials, controlled drug delivery, and photopharmacology, leveraging their light-responsive properties for dynamic and targeted functionalities [ 79 , 80 , 81 , 82 ]. The design of photoswitchable fluorescent probes based on Hemithioindigo molecular switches primarily involves incorporating heteroatomic rings such as pyridine, imidazole, and indole into the main structure of hemithioindigo to achieve light-regulated specific binding to targets.…”

Mechanistic Elucidation of the Hula-Twist Photoreaction in Hemithioindigo

“…To evidence other possible photochemical bond rotations, the Dube group developed the synthesis of double bond substituted HTIs and sulfur oxidized HTIs (Scheme b) . By combining these two substitution patterns, it was possible to create derivatives containing a significantly pretwisted single bond, which cannot rotate easily in the ground state because of very strong steric hindrance.…”

“…18 To evidence other possible photochemical bond rotations, the Dube group developed the synthesis of double bond substituted HTIs 20 and sulfur oxidized HTIs (Scheme 1b). 21 By combining these two substitution patterns, it was possible to create derivatives containing a significantly pretwisted single bond, which cannot rotate easily in the ground state because of very strong steric hindrance. If this twisted stilbene fragment is additionally rendered nonsymmetric by different orthosubstituents such as in derivative 1 (Scheme 1 and Figure 1), atropisomers can be distinguished as diastereomers in these structures.…”