Ammonia-Gated Guanyl Hydrazone Photoisomerization Enables Sequential Solid-State Optical Response in Hydrogen-Bonded Organic Frameworks.

Abstract

Light-driven molecular switches enable precise and noninvasive regulation of molecular structure and function, and thus represent fundamental building blocks for stimuli-responsive photofunctional materials. However, translating molecular-level photoswitching into sequence-dependent macroscopic outputs in the solid state remains a formidable challenge. In this study, we report a supramolecular strategy that integrates guanyl hydrazone switches into hydrogen-bonded organic frameworks (HOFs) to overcome this limitation. A tetrasulfonate-substituted tetraphenylethylene anion (TPE4 -) is employed as the host scaffold, while guanyl hydrazone (G2) functions as the photoresponsive guest, affording a functional framework through cooperative assembly. This system leverages a reversible crystalline-amorphous phase transformation, triggered by acid-base stimuli, to gate the solid-state photoisomerization of G2. Upon activation, the configurational switching of G2 induces a cascade reorganization of the TPE4 - packing motifs, leading to pronounced and sequence-dependent modulation of both fluorescence and macroscopic coloration. In addition, the applicability of this system in information encryption has been demonstrated. This work expands the design paradigm of hydrazone-based photoswitches in the solid state and provides a supramolecular strategy for constructing intelligent optical materials with high information density and enhanced security.