Structure Modulation in Zn(II)–1,4-Bis(imidazol-1-yl)benzene Frameworks by Varying Dicarboxylate Anions

In the field of metal–organic frameworks (MOFs), one of the challenges is the fabrication of novel materials that display/correlate the prediction of structures and functionality. Usually, the structures of MOFs are influenced by the skeleton of ligands. In this article, five different dicarboxylic acids, namely, fumaric dioic acid (H2FUM), 2-aminoterephthalic acid (2-H2ATA), 1,4-naphthalenedicarboxylic acid (1,4-H2NAPDC), 1,2-benzenedicarboxylic acid (1,2-H2BDC), and oxalic acid (H2OX) are employed as the secondary auxiliary ligands to perform a systematic study on the structure diversities in the Zn­(II)–1,4-bis­(imidazol-1-yl)­benzene (L) frameworks. By introducing various secondary dicarboxylate anions in the Zn­(II)-L system, six new complexes {Zn­(L)­(FUM)}∞ (1), {Zn2(L)­(2-ATA)2}∞ (2), {Zn­(L)­(1,4-NAPDC)·H2O}∞ (3), {Zn2(L)­(1,4-NAPDC)2·2DMF}∞ (4), {Zn­(L)­(1,2-BDC)}∞ (5), and {Zn3(L)2(OX)3·H2O}∞ (6) were obtained. Complexes 1 and 3 possess three-dimensional (3D) 5-fold interpenetrating diamond frameworks. Complex 2 is a 3D 3-fold interpenetrating α-Po framework constructed by dinucear {Zn2} secondary building units (SBUs). Complex 4 exhibits a 3D 2-fold interpenetrating α-Po framework when DMF acts as the reaction solvent. Complex 5 shows a 3D framework with diamondoid topology, which includes L/Zn­(II)/L helical chains. Complex 6 presents an interesting 3D structure constructed from {Zn­(II)-OX-Zn­(II)} rod-shaped SBUs and L ligands as pillars. The diverse structures of these six complexes indicate that the skeleton of dicarboxylate anions plays a great role in the assembly of such different frameworks. Moreover, the fluorescence properties of the complexes 1–6 were investigated in the solid state.在金属有机框架（metal–organic frameworks, MOFs）领域，一大核心挑战在于制备可实现结构与功能预测相匹配的新型材料。通常而言，金属有机框架的结构受配体骨架的显著影响。本文选取五种不同的二元羧酸作为次级辅助配体，即富马二酸（fumaric dioic acid, H₂FUM）、2-氨基对苯二甲酸（2-aminoterephthalic acid, 2-H₂ATA）、1,4-萘二甲酸（1,4-naphthalenedicarboxylic acid, 1,4-H₂NAPDC）、1,2-苯二甲酸（1,2-benzenedicarboxylic acid, 1,2-H₂BDC）以及草酸（oxalic acid, H₂OX），针对Zn(II)-1,4-二(咪唑-1-基)苯（L）框架的结构多样性开展系统性研究。通过在Zn(II)-L体系中引入不同的二元羧酸根阴离子，成功得到六个新型配合物：{Zn(L)(FUM)}_∞ (1)、{Zn₂(L)(2-ATA)₂}_∞ (2)、{Zn(L)(1,4-NAPDC)·H₂O}_∞ (3)、{Zn₂(L)(1,4-NAPDC)₂·2DMF}_∞ (4)、{Zn(L)(1,2-BDC)}_∞ (5)以及{Zn₃(L)₂(OX)₃·H₂O}_∞ (6)。配合物1与3均具有三维（3D）5重穿插金刚石型框架。配合物2是由双核{Zn₂}次级构筑单元（secondary building units, SBUs）构建的三维3重穿插α-钋（α-Po）型框架。当以N,N-二甲基甲酰胺（DMF）作为反应溶剂时，配合物4呈现三维2重穿插α-Po型框架。配合物5展现出带有金刚石拓扑结构的三维框架，其中包含L/Zn(II)/L螺旋链。配合物6则由{Zn(II)-OX-Zn(II)}棒状次级构筑单元与作为柱撑配体的L配体构建出颇具趣味的三维结构。上述六个配合物的结构多样性表明，二元羧酸根的骨架在这类不同框架的组装过程中发挥着关键作用。此外，本文还对配合物1~6的固态荧光性能开展了研究。