Wang Chih-Chieh, Ke Szu-Yu, Feng Yun, Ho Mei-Lin, Chang Chung-Kai, Chuang Yu-Chun, Lee Gene-Hsiang
Department of Chemistry, Soochow University, Taipei 11102, Taiwan.
Instrumentation Center, National Taiwan University, Taipei 10617, Taiwan.
Polymers (Basel). 2019 Aug 19;11(8):1369. doi: 10.3390/polym11081369.
Two coordination polymers (CPs) with chemical formulas, [Ho(CO)(CO)(HO)]·4HO (1) and [Ho(CO)(HO)] (2), (CO = dianion of squaric acid, CO = oxalate), have been synthesized and their structures were determined by single-crystal X-ray diffractometer (XRD). In compound , the coordination environment of Ho(III) ion is eight-coordinate bonded to eight oxygen atoms from two squarate, one oxalate ligands and four water molecules. The squarates and oxalates both act as bridging ligands with -bis-monodentate and -chelating coordination modes, respectively, connecting the Ho(III) ions to form a one-dimensional (1D) ladder-like framework. Adjacent ladders are interlinked via O-HO hydrogen bonding interaction to form a hydrogen-bonded two-dimensional (2D) layered framework and then arranged orderly in an AAA manner to construct its three-dimensional (3D) supramolecular architecture. In compound 2, the coordination geometry of Ho(III) is square-antiprismatic eight coordinate bonded to eight oxygen atoms from five squarate ligands and three water molecules. The squarates act as bridging ligands with two coordination modes, -trismonodentate and --monodentate, connecting the Ho(III) ions to form a 2D bi-layered framework. Adjacent 2D frameworks are then parallel stacked in an AAA manner to construct its 3D supramolecular architecture. Hydrogen bonding interactions between the squarate ligands and coordinated water molecules in 1 and 2 both play important roles on the construction of their 3D supramolecular assembly. Compounds 1 and 2 both show remarkable ligand-enhanced photo-induced color-changing behavior, with their pink crystals immediately turning to yellow crystals under UV light illumination.
合成了两种化学式分别为[Ho(CO)(CO)(HO)]·4HO (1) 和[Ho(CO)(HO)] (2) 的配位聚合物（CPs）（CO为方酸二价阴离子，CO为草酸根），并通过单晶X射线衍射仪（XRD）确定了它们的结构。在化合物1中，Ho(III)离子的配位环境为八配位，与来自两个方酸根、一个草酸根配体和四个水分子的八个氧原子键合。方酸根和草酸根分别作为桥联配体，以 -双单齿和 -螯合配位模式连接Ho(III)离子，形成一维（1D）梯状框架。相邻的梯子通过O-HO氢键相互作用相互连接，形成氢键二维（2D）层状框架，然后以AAA方式有序排列，构建其三维（3D）超分子结构。在化合物2中，Ho(III)的配位几何形状为反棱柱方形八配位，与来自五个方酸根配体和三个水分子的八个氧原子键合。方酸根作为具有两种配位模式的桥联配体，即 -三单齿和 --单齿，连接Ho(III)离子，形成二维双层框架。相邻的二维框架然后以AAA方式平行堆叠，构建其三维超分子结构。1和2中方酸根配体与配位水分子之间的氢键相互作用在其三维超分子组装的构建中都起着重要作用。化合物1和2都表现出显著的配体增强光致变色行为，其粉红色晶体在紫外光照射下立即变为黄色晶体。
