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Two Photochromic Complexes Assembled by a Nonphotochromic Ligand: Photogenerated Radical Enhanced Room-Temperature Phosphorescence

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journal contribution
posted on 22.12.2020, 19:39 by Wu-Ji Wei, Ying Mu, Li Wei, Ji-Xiang Hu, Guo-Ming Wang
Stimulating tunable room-temperature phosphorescence (RTP) is still a challenge in photochromic systems, which is vital for multifunctional coordination materials. Herein, we synthesized two new photochromic chain complexes through self-assembly of the nonphotochromic 1,3,5-tris­(4-pyridyl)­benzene ligand, diphosphonate, and Ln­(III) ions (1 for Ln­(III) = Dy and 2 for Ln­(III) = Gd). Both compounds showed fast photoresponses with the color turning from yellow to dark gray with a reversible decoloration by heating or storage in the dark. The electron transfer photochromic behavior with the generated stable radicals was further confirmed by the room-temperature UV–vis and electron paramagnetic resonance spectra. Furthermore, via tuning the generation and disappearance of stable radicals, reversible room-temperature fluorescence and phosphorescence for both compounds were switched by light irradiation and a thermal treatment, with an enhanced intensity for RTP and a decrease in fluorescence during the duration of Xe-lamp light irradiation. This work provides a new strategy that photogenerated radicals could promote and enhance RTP properties in functional materials.