Conformational Dynamics of o-Fluoro-Substituted Z-Azobenzene

Visible Light Mediated Bidirectional Control over Carbonic Anhydrase Activity in Cells and in Vivo Using Azobenzenesulfonamides

Two azobenzenesulfonamide molecules with thermally stable cis configurations resulting from fluorination of positions ortho to the azo group are reported that can differentially regulate the activity of carbonic anhydrase in the trans and cis configurations. These fluorinated probes each use two distinct visible wavelengths (520 and 410 or 460 nm) for isomerization with high photoconversion efficiency. Correspondingly, the cis isomer of these systems is highly stable and persistent (as evidenced by structural studies in solid and solution state), permitting regulation of metalloenzyme activity without continuous irradiation. Herein, we use these probes to demonstrate the visible light mediated bidirectional control over the activity of zinc-dependent carbonic anhydrase in solution as an isolated protein, in intact live cells and in vivo in zebrafish during embryo development.

Computational Design and Synthesis of a Deeply Red-Shifted and Bistable Azobenzene

We computationally dissected the electronic and geometrical influences of ortho-chlorinated azobenzenes on their photophysical properties. X-ray analysis provided the insight that trans-tetra-ortho-chloro azobenzene is conformationally flexible and thus subject to molecular motions. This allows the photoswitch to adopt a range of red-shifted geometries, which account for the extended n → π* band tails. On the basis of our results, we designed the di-ortho-fluoro di-ortho-chloro (dfdc) azobenzene and provided computational evidence for the superiority of this substitution pattern to tetra-ortho-chloro azobenzene. Thereafter, we synthesized dfdc azobenzene by ortho-chlorination via 2-fold C–H activation and experimentally confirmed its structural and photophysical properties through UV–vis, NMR, and X-ray analyses. The advantages include near-bistable isomers and an increased separation of the n → π* bands between the trans- and cis-conformations, which allows for the generation of unusually high levels of the cis-isomer by irradiation with green/yellow light as well as red light within the biooptical window.

Controlling azobenzene photoswitching through combined ortho-fluorination and -amination

We present a series of visible-light-absorbing azobenzenes through a combination of ortho-fluorination and –amination showing a wide range of cis-lifetimes.