Polymeric Luminescent Zn(II) and Cd(II) Dicarboxylates Decorated by Oxime Ligands: Tuning the Dimensionality and Adsorption Capacity

Ten Zn­(II) and Cd­(II) metal–organic materials were synthesized and studied by the X-ray method. Among these 10 structures, two represent binuclear clusters, and two are one-dimensional (1D) coordination polymers, while five are laminar two-dimensional (2D) solids and one is the three-dimensional (3D) framework. The investigation has been aimed at rational design of coordination polymers decorated by oxime ligands to increase the accessible adsorption area in these newly synthesized solids. The ligands used include three aliphatic dicarboxylic acids, HOOC-(CH2)n-COOH [n = 1, 2, 4 corresponding to malonic (H2mal), succinic (H2suc), and adipic (H2adi) acids], and three neutral oxime ligands [pyridine-2-aldoxime (2-pyao), pyridine-4-aldoxime (4-pyao), and 1,2-cyclohexanedionedioxime (Niox)]. These novel hybrid solids with the compositions [Zn2(suc)2­(2-pyao)4]­·2H2O 1, [Cd2(suc)­(2-pyao)4(H2O)2]­[BF4]2 2, [Cd­(suc)­(2-pyao)2]n 3, [Zn­(mal)­(4-pyao)­(H2O)]n 4, [Cd­(mal)­(4-pyao)­(H2O)]n 5, [Zn­(suc)­(4-pyao)]n 6, [Zn­(adi)­(4-pyao)2]n 7, {[Cd­(adi)­(4-pyao)2]·dmf}n 8, [Zn­(adi)­(Niox)]n 9, and [Cd­(adi)­(Niox)]n 10 [dmf – N,N′-dimethylformamide] demonstrate a variable class of coordination supramolecular architectures dictated by the distinctions in the metals’ and oxime ligands’ coordination capacities and preferences, and length and flexibility of the dicarboxylic linkers. The discrete aggregates 1 and 2 differ by the components’ ratio and conformation of the bridging succinate anion; compounds 3 and 7 are 1D arrays, and compounds 4, 5, 6, 8, and 9 represent 2D layers of different topologies. Compound 10 is a 3D grid afforded by the concerted contribution of the longest in this series adipate anion, and the bigger atomic radius Cd­(II) vs. Zn­(II). The adsorptive properties of 7 and 9 are reported. For the laminar solid 9, the quantum chemical simulations of the adsorption capacity are in line with the experimental results. All new materials reveal dual green-blue wavelength emission in the solid state.本研究合成了10种锌(II)与镉(II)基金属有机材料，并采用X射线衍射方法对其开展了表征与研究。在这10种晶体结构中，2种为双核簇合物，2种为一维（1D）配位聚合物，5种为层状二维（2D）固体，剩余1种为三维（3D）骨架结构。本研究的目标是通过肟类配体修饰配位聚合物，以提升此类新合成固体材料的可及吸附表面积。本次实验所用配体包括三类脂肪族二羧酸：HOOC-(CH₂)ₙ-COOH [其中n=1、2、4分别对应丙二酸（H₂mal）、丁二酸（H₂suc）与己二酸（H₂adi）]，以及三类中性肟类配体：吡啶-2-甲醛肟（2-pyao）、吡啶-4-甲醛肟（4-pyao）与1,2-环己二酮二肟（Niox）。上述新型杂化固体的化学式依次为：1. [Zn₂(suc)₂(2-pyao)₄]·2H₂O；2. [Cd₂(suc)(2-pyao)₄(H₂O)₂][BF₄]₂；3. [Cd(suc)(2-pyao)₂]ₙ；4. [Zn(mal)(4-pyao)(H₂O)]ₙ；5. [Cd(mal)(4-pyao)(H₂O)]ₙ；6. [Zn(suc)(4-pyao)]ₙ；7. [Zn(adi)(4-pyao)₂]ₙ；8. {[Cd(adi)(4-pyao)₂]·dmf}ₙ（dmf即N,N'-二甲基甲酰胺）；9. [Zn(adi)(Niox)]ₙ；10. [Cd(adi)(Niox)]ₙ。这些材料展现出多样化的配位超分子架构，其结构差异由金属离子与肟类配体的配位能力及配位偏好、二羧酸连接体的链长与柔性共同决定。离散聚集体1与2的差异在于组分比例以及桥联丁二酸根阴离子的构象；化合物3与7为一维链状阵列结构，化合物4、5、6、8与9则为不同拓扑结构的二维层状结构。化合物10为三维网格结构，其形成得益于本系列中最长的己二酸根阴离子，以及镉(II)相较于锌(II)更大的原子半径。本文报道了化合物7与9的吸附性能，针对层状固体9，其吸附容量的量子化学模拟结果与实验数据吻合良好。所有新型材料在固态下均展现出双发射的绿蓝色波段荧光。