Dynamic Ultralong Phosphorescence and Optical Waveguiding Switches in Silver‐Organic Complex via Reversible Single‐Crystal‐to‐Single‐Crystal Conversion

Abstract Dynamic ultralong room‐temperature phosphorescent (RTP) materials with stimuli‐responsive properties have attracted considerable interest for applications in sensors, light‐emitting devices, and information security. Here, we introduce a novel class of silver (Ag)‐organic complexes exhibiting rare, direct ultralong RTP, achieved through the heavy‐atom effect of Ag + ions and highly ordered assembly of coordination polymers. The Ag‐based complex displays reversible solvent‐responsive RTP, shifting from green to yellow emission in response to humidity and solvent variations. This transformation is driven by a solvent‐mediated single‐crystal‐to‐single‐crystal (SCSC) conversion, enabling color‐tunable active optical waveguides and one‐dimensional (1D) polarization switching. Therefore, this study provides a new strategy for creating dynamically controllable ultralong all‐phosphorescent metal‐organic complexes and advances the design of stimuli‐responsive 1D photonic systems for promising information encryption and anti‐counterfeiting applications.