Metallo-hydrogels represent an attractive class of soft materials with tailorable properties, such as optical, self-healing, magnetic and catalytic activities. Herein, we present on the preparation of a new type hybrid metallo-hydrogels based on phenylalanine derivative containing an imidazole group (IM-PF) modified with a photo-switchable arylazopyrazole (AAP) moiety with potential gel-to-sol transitions triggered by light. It was found that although the IM-PF derivative alone or mixed with the AAP photo-switches could not form a hydrogel, when mixed with zinc salts they readily form metallo-hydrogels, showing a pivotal role of the Zn(II) on in the gelation process. Sonication of the phenylalanine based-gelator and the AAP photo-switches with different zinc salts resulted in the facile formation of metallo-hydrogels. We also screened different zinc salts to explore the effect of anions on gelation. The results revealed that the gelation process is independent of the type of zinc salts used. The photo-responsive behavior of both the metallo-hydrogels and AAP was also studied by UV-vis Spectroscopy. Upon Irradiation with UV light (l = 365 nm) the AAP photo-switches undergoes efficient trans-to-cis photo-isomerization. However, the light-induced gel-to-sol transition of the metallo-hydrogel was slightly inhibited. The effect of the nature of the substituents of the AAP ligand structure on the gelation and the trans-to-cis isomerization processes has also been explored and the results of our findings will be discussed.

Phenylalanine-based metallo-hydrogels with photo-switchable arylazopyrazole ligands

2019 Fall National Meeting

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