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.