Skip to main content
. 2022 Feb 15;61(15):e202113076. doi: 10.1002/anie.202113076

Figure 1.

Figure 1

Restricting photoreactivity of halochromic styrylpyridopyrazine (SPP) using a photoacid generator and application in hydrogel design. A) MeO‐PEG‐SPP can undergo photocycloaddition by visible light at 400–550 nm and pH≥7. In the presence of a PAG (λ activation=400–510 nm) that lowers the pH (≤6), the photoreactivity of the SPP is inhibited; however, green light at 520–550 nm can still activate the photocycloaddition. Thus, the PAG effectively restricts the photoreactivity of MeO‐PEG‐SPP in the 520–550 nm window. B) The SPP group is attached to an 8‐arm PEG together with a non‐halochromic acrylamidylpyrene (AP), which can undergo photocycloaddition by blue light (400–470 nm), and the photoreactivity of the AP is not affected when mixed with the PAG. In the presence of the PAG, the 8‐arm PEG‐AP‐SPP can crosslink by either blue or green light via photocycloaddition of the AP or SPP group, respectively.