Photoswitching, Umpolung and Reversible Self-Assembly of Gold Nanoparticles Covered With Thiolated Donor-Acceptor Stenhouse Adducts

The possibility of incorporating functional groups into molecular photoswitches is a prerequisite for their versatility and broad-range applications. Herein we present the first successful synthesis of DASA chromophores featuring a thiol group. The latter provides a unique opportunity to investigate the photoswitching behavior of these visible-light operating chromophores on the surface of metallic nanoparticles. This behavior can be modulated by irradiation time, solvent composition, DASAs population, and the organic layer underneath the chromophores. Moreover, the changes in polarity induced by DASAs photoisomerization are translated onto the colloidal particles giving rise to unusual interfacial and bulk-phase phenomena, including nonlinear solubility effects and reversible agglomeration that takes place in a time-controllable fashion. These findings pave the way for the rational design of new photoresponsive and smart materials.