Fourfold Double-Bond Substituted Hemiindigo: Highly Functionalized Red-Light Responsive Photoswitches

Abstract

Molecular photoswitches are indispensable tools for responsive chemical nanosystems and are nowadays used in virtually all branches of the natural sciences. Hemiindigo (HI) derivatives were recently introduced as potent photoswitches but full applicability was hampered by the limited possibilities for their functionalization and structural alteration. Here we report on a short and easy to diversify synthesis yielding fourfold double-bond substituted HIs. The resulting chromophores are shown to offer an advantageous property profile combining red-light responsiveness, high thermal bistability, strong isomer accumulations in both switching directions, and strong photochromism. With this progress a new structural realm has been opened up for HI photoswitches, that can now be synthetically tailored to highly advanced applications in e.g. molecular machines and multi-switching research, photoisomerization mechanism studies, or smart and addressable materials generation.

Peri-Anthracenethioindigo: a Scaffold for Efficient All-Red-Light and NIR Molecular Photoswitching

“…As the field of photoswitch research progressed a large portion of work has been aimed at developing thermally stable and red-or near infrared (NIR)-light responsive variants in the last decade and this research continues to be a hot topic to date. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Bistable red/NIR-light responsiveness is crucial for many application areas that do not tolerate higher energy UV or visible light, especially in materials research, 19,20 chemical biology, 5,21 photopharmacology, [22][23][24] and catalysis. 25 Further, such red-shifted photoswitches can be combined with different photoresponsive components, e.g.…”

“…other photoswitches, 26 fluorophores, 27 or photocatalysts 19 that need to be addressed individually. To elicit red-light responsiveness direct excitation [6][7][8][9][10][11][12][13][14][15][16][17]28 is highly desirable but also sensitization or two-photon processes [29][30][31] can be efficient to realize red-light responsiveness. So far however, red/NIRlight responsive photoswitches still require higher energy UV or visible light for the reverse switching direction.…”