No abstract

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.

Photoswitchable room temperature phosphorescence (RTP) materials are of great interest due to their potential applications in optical devices and switches. Herein, two Zn‐based coordination polymers (CPs) (H3‐TPB)·[Zn6(H‐HEDP)(HEDP)3(H2O)2]·5H2O (complex 1; HEDP = hydroxyethylidene diphosphonate; TPB = 1,3,5‐tris(4‐pyridyl)benzene) and (H‐TPB)·[Zn3(H‐HEDP)(HEDP)(H2O)]·2H2O (complex 2) with distinguishable photochromism and tunable RTP are synthesized involving photoactive TPB molecules with different packing modes. Complex 1 exhibits bidirectionally on/off RTP regulation via on‐switch with excitation of 250−330 nm light and off‐switch with 350−380 nm, and the “turn‐on” behavior can be attributed to the advance of Förster resonance energy transfer‐assisted intersystem crossing (ISC) process while “turn‐off” process due to the transformation from H3‐TPB cations to H3‐TPB· radicals. Complex 2 exhibits photoswitchable RTP accompanied with reversible photochromism by leveraging the self‐absorption and RTP emission. Two demos based on the above compounds are further applied to demonstrate the application in information recording and encryption fields. This work supplies a strategy toward the design of switchable RTP systems using electron transfer photochromism, shedding light on broadening the frontiers of photoresponsive materials.

Photomagnetic materials have attracted enormous attention due to the adjustable coloration and magnetization via light irradiation, while challenges still exist for drastically tuning the magnetism at room temperature. Herein, a novel multifunctional crystal complex (H2− = oxalate and TPB = 1,3,5-tris(4-pyridyl)benzene) is constructed by selfassembly of paramagnetic Fe 3+ ions, electron donor oxalate, and electron acceptor TPB ligands. After light irradiation, the compound 1 undergoes unidirectional electron transfer (ET) from oxalate to TPB ligands and Fe 3+ ions, which not only results in the decomposition of oxalate and generation of radicals and Fe 2+ species but also leads to remarkable ET-triggered photochromism. Importantly, room temperature light irradiation changes the magnetic behavior of 1 from weak to strong antiferromagnetism. Moreover, thanks to the stability of the photogenerated radicals, the photoresponsive proton conductivity property for 1 is also explored and photoenhanced proton conductivity is observed after photoirradiation.

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.