Achieving magnetic bistability with large thermal hysteresis is still a formidable challenge in material science. Here we synthesize a series of isostructural chain complexes using 9,10-anthracene dicarboxylic acid as a photoactive component. The electron transfer photochromic Mn2+ and Zn2+ compounds with photogenerated diradicals are confirmed by structures, optical spectra, magnetic analyses, and density functional theory calculations. For the Mn2+ analog, light irradiation changes the spin topology from a single Mn2+ ion to a radical-Mn2+ single chain, further inducing magnetic bistability with a remarkably wide thermal hysteresis of 177 K. Structural analysis of light irradiated crystals at 300 and 50 K reveals that the rotation of the anthracene rings changes the Mn1–O2–C8 angle and coordination geometries of the Mn2+ center, resulting in magnetic bistability with this wide thermal hysteresis. This work provides a strategy for constructing molecular magnets with large thermal hysteresis via electron transfer photochromism.

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The tris­(pyridin-4-yl)­amine ligand was found to exhibit a radical-actuated coloration phenomenon, and a novel copper-based color-changeable metal–organic framework (MOF) was synthesized via this photoactive ligand. After light irradiation, the photogenerated stable radicals in this framework induced increasing amplitude of magnetization (32%) at room temperature, being the largest enhancement among radical-based photochromic systems.

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Hydroxyethylidene diphosphonate (HEDP) and tris(4pyridyl)amine (TPA) are employed to assist the preparation of a Dy(III)-phosphonate in this work, namely, {[Dy 2 (H 2 -HEDP) 4 ] 3 •2(H 3 -TPA)•2(H 4 -HEDP)•xsolvent} (1). The compound features the anionic one-dimensional chain structure templated by the cationic H 3 -TPA and uncoordinated H 4 -HEDP molecules. Through the hydrogen bonds between the guest cations and host Dy(III)-phosphonate skeletons, a supramolecular architecture is finally constructed, displaying photochromism and room-temperature phosphorescence (RTP) behaviors. Interestingly, through the protonation of TPA molecules, the radicals generated after photochromism still remain a highly stable character, accomplishing an extremely long-lived state of charge separation. Moreover, the photogenerated radicals can greatly prompt the RTP performance of compound 1, which offers a promising strategy for the construction of tunable optical materials.