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.
Inorg Chem. 2012 Apr 2;51(7):4015-9. doi: 10.1021/ic2020868. Epub 2012 Mar 12.
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)(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.
N-甲基-4,4'-联吡啶鎓（MQ(+))盐及其金属配合物的光致变色性从未被报道过。一系列 MQ(+)配位卤化锌配合物[(MQ)ZnX(3)]（X = Cl（1），Br（2），I（3））和[(MQ)ZnCl(1.53)I(1.47)]（2）[(MQ)ZnCl(1.68)I(1.32)]（4）被发现具有不同的光致变色行为，它们比 MQ(+)阳离子的卤化物盐具有更好的物理化学稳定性。化合物 1-3 是同构的，但只有 1 和 2 显示出光致变色性。向非光致变色化合物 3 中引入部分 Cl 原子得到化合物 4，它也显示出光致变色性。1、2 和 4 的光致变色响应表明存在它们的长寿命电荷分离态，根据 ESR 和 XPS 测量，这些电荷分离态源于 X → MQ(+)电子转移。对不同配位卤原子影响的研究表明，Cl 原子可能是比 Br 和 I 原子更适合的电子供体，可用于设计氧化还原光致变色金属配合物。
