Photochromic metal complexes of N-methyl-4,4'-bipyridinium: mechanism and influence of halogen atoms |
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Authors: | Lv Xiang-Ying Wang Ming-Sheng Yang Chen Wang Guan-E Wang Shuai-Hua Lin Rong-Guang Guo Guo-Cong |
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Institution: | State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China. |
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Abstract: | Photochromism of N-methyl-4,4'-bipyridinium (MQ(+)) salts and their metal complexes has never been reported. A series of MQ(+) coordinated halozinc complexes (MQ)ZnX(3)] (X = Cl (1), Br (2), I (3)) and (MQ)ZnCl(1.53)I(1.47)](2)(MQ)ZnCl(1.68)I(1.32) (4), with better physicochemical stability than halide salts of the MQ(+) cation, have been found to exhibit different photochromic behaviors. Compounds 1-3 are isostructural, but only 1 and 2 show photochromism. Introduction of partial Cl atoms to nonphotochromic compound 3 yields compound 4, which also displays photochromism. The photochromic response of 1, 2, and 4 indicates the presence of their long-lived charge separation states, which originate from X → MQ(+) electron transfer according to ESR and XPS measurements. Studies on the influence of different coordinated halogen atoms demonstrate that the Cl atom may be a more suitable electron donor than Br and I atoms to design redox photochromic metal complexes. |
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