Photolabile amphiphiles with fluorogenic thioxanthone-dithiane functionality: synthesis and photoinduced fragmentation in micelles

Abstract

Novel photolabile amphiphiles containing thioxanthone-based fluorogenic caging groups are developed. Photoinduced fragmentation in dithiane-thioxanthone adducts was demonstrated to occur with 100% quantum efficiency at λ ~ 320 nm and more than 50% at λ ~ 360 nm. A plausible mechanism involves homolytic fission of a carbon-carbon single bond in the excited thioxanthone followed by disproportionation via hydrogen transfer. The critical feature of the system is that fluorescence of a substituted thioxanthone is recovered as a result of photofragmentation, making dithiane-thioxanthone adducts efficient fluorogenic caging groups. Photolabile amphiphiles containing these fluorogens are synthesized and their photoinduced disassembly is probed while following the fluorescence recovery. This methodology allows for destabilizing supramolecular assemblies of amphiphiles and at the same time offers a feedback mechanism for monitoring the process by fluorescence.

Photoremovable Protecting Groups in Chemistry and Biology: Reaction Mechanisms and Efficacy

“…The dithiane-based linkers were explored for various applications, such as photolabile phospholipids and amphiphiles, calixarene-based rosette, or barbiturate receptors . Dithiane-spiro-crown ethers (e.g., 264 ; Scheme ) were used as photolabile moieties, which allowed photochemical interruption of transport through liquid membranes, or as photolabile linkers …”