Stimulus-responsive viologen coordination polymers (CPs) have been very popular in the past few years due to the increasing demand for smart materials. In order to obtain such CPs, in this work, a flexible carboxybenzyl viologen ligand 1,1′-bis(4-carboxybenzyl)-4,4′-bipyridinium dichloride (H₂BpybcCl₂), and its self-assembly with transition metal ions in the presence of 1,4-benzenedicarboxylic acid (p-H₂BDC) leads to the formation of three novel isostructural CPs {[TM₄(Bpybc)₆(H₂O)₁₂]·(OH)₂·(p-BDC)₃·22H₂O}_n (TM = Co (1), Ni (2), Mn (3)). Each Bpybc ligand bridges two metal ions to create an infinite two-dimensional network. Due to the formation of Bpybc radicals, all three compounds are photochromic under UV irradiation. At the same time, the three compounds exhibit unique hydrochromic properties. The reversible color changes are caused by both electron transfer and the modulation of d–d transitions in the ligand field through dehydration and rehydration accompanied by structure transformations.

由于对智能材料的需求不断增长，刺激响应的紫精配位聚合物（CP）在过去几年中非常受欢迎。为了获得此类CP，在这项工作中，使用了柔性的羧基苄基紫精配体1,1'-双（4-羧基苄基）-4,4'-二氯化联吡啶鎓（H ₂ BpybcCl ₂），及其与过渡金属的自组装离子在1,4-苯二甲酸（p -H ₂ BDC）的存在下会导致形成三个新的同构CPs [[TM ₄（Bpybc）₆（H ₂ O）₁₂ ]·（OH）₂ ·（p -BDC）₃ ·22H ₂ O} _n（TM ＝ Co（1），Ni（2），Mn（3））。每个Bpybc配体桥接两个金属离子以创建一个无限的二维网络。由于Bpybc自由基的形成，这三种化合物在UV照射下都是光致变色的。同时，这三种化合物表现出独特的水致变色性质。可逆的颜色变化是由于电子转移和配体场中的d–d跃迁通过脱水和再水化以及结构转变而引起的。