Orange-Light-Induced Photochemistry Gated by pH and Confined Environments

We introduce a new photochemically active compound, i.e., pyridinepyrene (PyPy), entailing a pH-active moiety that effects a significant halochromic shift into orange-light (lambda = 590 nm) activatable photoreactivity while concomitantly exerting control over its reaction pathways. With blue light (lambda = 450 nm) in neutral to basic pH, a [2 + 2] photocycloaddition can be triggered to form a cyclobutene ring in a reversible fashion. If the pH is decreased to acidic conditions, resulting in a halochromic absorption shift, photocycloaddition on the small-molecule level is blocked due to repulsive interactions and exclusive trans-cis isomerization is observed. Through implementation of PyPy into the confined environment of a single-chain nanoparticle (SCNP) design, one can overcome the repulsive forces and exploit the halochromic shift for orange light (lambda = 590 nm)-induced cycloaddition and formation of macromolecular three-dimensional (3D) architectures.

Automated summary

This article introduces a novel photochemically active compound, PyPy, which possesses a pH-active moiety to control the reaction pathways. By incorporating PyPy into the design of single-chain nanoparticles, the repulsive forces can be overcome and the halochromic shift can be utilized to induce chemical reactions.