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

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.