Novel Viologen Derivative Based Uranyl Coordination Polymers Featuring Photochromic Behaviors

Abstract A series of novel uranyl coordination polymers have been synthesized by hydrothermal reactions. Both complexes 1 and 2 prosess two ipbp − ligands (H 2 ipbpCl=1‐(3,5‐dicarboxyphenyl)‐4,4′‐bipyridinium chloride), one uranyl cation, and two coordination water molecules, which can further extend to 2D networks through hydrogen bonding. In complex 1 , two sets of equivalent nets are entangled together, resulting in a 2D + 2D → 3D polycatenated framework. In complex 2 , the neighbouring equivalent nets interpenetrate each other, forming a twofold interpenetrated network. Complexes 3 and 4 are isomers, and both of them are constructed from (UO 2 ) 2 (OH) 2 dinuclear units, which are connected with four ipbp − ligands. The 3D structures of complexes 3 and 4 are similar along the b axis. Similar to other viologen‐based coordination polymers, complexes 3 and 4 exhibit photochromic and thermochromic properties, which are rarely observed in actinide coordination polymers. Unlike the monotonous coordination mode in complexes 1 – 4 , the ipbp − ligands feature a μ 3 ‐bridge through two kinds of coordination modes in complex 5 . Notably, complex 5 presents a unique example in which terminal pyridine nitrogen atom is involved in the coordination.