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

Abstract

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 (<b>L</b>) frameworks. By introducing various secondary dicarboxylate anions in the Zn­(II)-<b>L</b> system, six new complexes {Zn­(<b>L</b>)­(FUM)}_∞ (<b>1</b>), {Zn₂(<b>L</b>)­(2-ATA)₂}_∞ (<b>2</b>), {Zn­(<b>L</b>)­(1,4-NAPDC)·H₂O}_∞ (<b>3</b>), {Zn₂(<b>L</b>)­(1,4-NAPDC)₂·2DMF}_∞ (<b>4</b>), {Zn­(<b>L</b>)­(1,2-BDC)}_∞ (<b>5</b>), and {Zn₃(<b>L</b>)₂(OX)₃·H₂O}_∞ (<b>6</b>) were obtained. Complexes <b>1</b> and <b>3</b> possess three-dimensional (3D) 5-fold interpenetrating diamond frameworks. Complex <b>2</b> is a 3D 3-fold interpenetrating α-Po framework constructed by dinucear {Zn₂} secondary building units (SBUs). Complex <b>4</b> exhibits a 3D 2-fold interpenetrating α-Po framework when DMF acts as the reaction solvent. Complex <b>5</b> shows a 3D framework with diamondoid topology, which includes <b>L</b>/Zn­(II)/<b>L</b> helical chains. Complex <b>6</b> presents an interesting 3D structure constructed from {Zn­(II)-OX-Zn­(II)} rod-shaped SBUs and <b>L</b> 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 <b>1</b>–<b>6</b> were investigated in the solid state