Zhang Zheng, Zhao Lei, Yu Hai Yan, Zhang Hong Tao
College of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui 241000, People's Republic of China.
Acta Crystallogr C Struct Chem. 2024 Oct 1;80(Pt 10):633-647. doi: 10.1107/S2053229624008003. Epub 2024 Sep 4.
Two new two-dimensional (2D) coordination polymers (CPs), namely, poly[diaqua[μ-2,2'-(1,3,5,7-tetraoxo-1,2,3,5,6,7-hexahydropyrrolo[3,4-f]isoindole-2,6-diyl)diacetato-κO:O':O'':O''']cadmium(II)], [Cd(CHNO)(HO)] (1), and poly[[tetraaqua[μ-2,2'-(1,3,5,7-tetraoxo-1,2,3,5,6,7-hexahydropyrrolo[3,4-f]isoindole-2,6-diyl)diacetato-κO:O':O'':O'''][μ-2,2'-(1,3,5,7-tetraoxo-1,2,3,5,6,7-hexahydropyrrolo[3,4-f]isoindole-2,6-diyl)diacetato-κO:O']dizinc(II)] dihydrate], {[Zn(CHNO(HO)]·HO} (2), have been synthesized by the microwave-irradiated reaction of Cd(CHCOO)·2HO and Zn(CHCOO)·2HO, respectively, with N,N'-bis(glycinyl)pyromellitic diimide {BGPD, namely, 2,2'-(1,3,5,7-tetraoxo-1,2,3,5,6,7-hexahydropyrrolo[3,4-f]isoindole-2,6-diyl)diacetic acid, HL}. In the crystal structure of 1, the Cd ion is six-coordinated by four carboxylate O atoms from four symmetry-related L dianions and two coordinated water molecules, furnishing an octahedral coordination geometry. The bridging L dianion links four symmetry-related Cd cations into a 2D layer-like structure with a 3,4-connected bex topology. In the crystal structure of 2, the Zn ion is five-coordinated by three carboxylate O atoms from three different L dianions and two coordination water molecules, furnishing a trigonal bipyramidal coordination geometry. Two crystallographically independent ligands serve as μ- and μ-bridges, respectively, to connect the Zn ions, thereby forming a 2D layer with a 3,3-connected hcb topology. Crystal structure analysis reveals the presence of n→π* interactions between two carbonyl groups of the pyromellitic diimide moieties in 1 and 2. CP 1 exhibits an enhanced fluorescence emission compared with free HL. The framework of 2 decomposes from 720 K, indicating its high thermal stability. A comparative analysis of a series of structures based on the BGPD ligand indicates that the metal-ion size has a great influence on the connection modes of the metal ions due to different steric effects, which, in turn, affects the structures of the SBUs (secondary building units) and frameworks.
通过分别将Cd(CH₃COO)₂·2H₂O和Zn(CH₃COO)₂·2H₂O与N,N'-双(甘氨酰基)均苯四甲酸二酰亚胺{BGPD，即2,2'-(1,3,5,7-四氧代-1,2,3,5,6,7-六氢吡咯并[3,4-f]异吲哚-2,6-二基)二乙酸，HL}进行微波辐射反应，合成了两种新型二维(2D)配位聚合物(CPs)，即聚[二水合[μ-2,2'-(1,3,5,7-四氧代-1,2,3,5,6,7-六氢吡咯并[3,4-f]异吲哚-2,6-二基)二乙酸根-κO:O':O'':O''']镉(II)]，[Cd(C₁₂H₈N₂O₈)(H₂O)₂] (1)，以及聚[[四水合[μ-2,2'-(1,3,5,7-四氧代-1,2,3,5,6,7-六氢吡咯并[3,4-f]异吲哚-2,6-二基)二乙酸根-κO:O':O'':O'''][μ-2,2'-(1,3,5,7-四氧代-1,2,3,5,6,7-六氢吡咯并[3,4-f]异吲哚-2,6-二基)二乙酸根-κO:O']二锌(II)]二水合物]，{[Zn₂(C₁₂H₈N₂O₈)(H₂O)₄]·2H₂O} (2)。在1的晶体结构中，Cd离子由来自四个对称相关的L二价阴离子的四个羧酸根O原子和两个配位水分子六配位，形成八面体配位几何构型。桥连的L二价阴离子将四个对称相关的Cd阳离子连接成具有3,4-连接的bex拓扑结构的二维层状结构。在2的晶体结构中，Zn离子由来自三个不同L二价阴离子的三个羧酸根O原子和两个配位水分子五配位，形成三角双锥配位几何构型。两个晶体学独立的配体分别作为μ-和μ-桥连接Zn离子，从而形成具有3,3-连接的hcb拓扑结构的二维层。晶体结构分析表明，1和2中均苯四甲酸二酰亚胺部分的两个羰基之间存在n→π*相互作用。与游离的HL相比，CP 1表现出增强的荧光发射。2的骨架在720 K开始分解，表明其具有高热稳定性。基于BGPD配体的一系列结构的对比分析表明，由于不同的空间效应，金属离子尺寸对金属离子的连接方式有很大影响，进而影响次级结构单元(SBUs)和骨架的结构。
