Achieving an electron transfer photochromic complex for switchable white-light emission

Tuning white-light emission via free radicals is still a challenge in molecular-based functional materials. Herein, a new photoactive Zn2+ oxalate-based chain containing a polypyridine ligand was designed and synthesized with remarkably bifunctional photochromism and photo-actuated greenish white-light emission after UV, sunlight or Xe lamp light irradiation at room temperature. The photo-actuated coloration process was induced by the photogeneration of stable radicals originated from intermolecular electron transfers from oxalate components to the protonated polypyridine units, as demonstrated by UV–vis, IR, electron spin resonance and X-ray photoelectron spectra and magnetic measurements. Importantly, the on/off greenish white light emission (WLE) could be reversibly switched by generation and elimination of radicals via light irradiation and heat treatment, providing a feasible strategy for designing photoswitchable light emission diodes materials.