Synthesis, Crystal Structures, and Properties of a New Supramolecular Polymer Based on Mixed Imidazole and Carboxylate Ligands

Mei-An Zhu,Shan-Shan Shi,Jin Mei,Shui-Sheng Chen,Shuai-Shuai Han

doi:10.3390/cryst7070210

Abstract

One new coordination polymer, namely, [Cd3(H2L)3(Pza)2(H2O)2]n (1) was synthesized by the reaction of Cd(NO3)2·4H2O with 1,4-di(1H-imidazol-4-yl)benzene (H2L) and 3,5-pyrazoledicarboxylic acid (H3pza) and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis, and powder X-ray diffraction (PXRD). The H3pza ligand was completely deprotonated to pza3−, which bridged the Cd2+ to form one-dimensional (1D) chain. The adjacent 1D chains were further linked into the two-dimensional (2D) layer by the linear H2L ligands. The weak interaction, including hydrogen bonds and π−π stacking interactions, extends the 2D layers into three-dimensional (3D) supramolecular polymer. Complex 1 shows intense light blue emission in the solid state at room temperature.

Highlights

In the recent years, rational design and successful construction of metal-organic frameworks (MOFs) has become an expanding research topic in the fields of synthetic chemistry and materials science because of their intriguing variety of architectures and captivating topologies and their potentially multi-field applications in numerous areas in fluorescence, gas adsorption/separation, magnetic properties, electrochemistry, catalysis, and so on [1,2,3,4,5,6,7,8]
The MOFs possessing versatile structures and desired properties are mainly dependent on the appropriate organic linkers [9,10], and the external synthesis conditions such as pH values, molar ratio of reactants, reaction temperatures, solvent system, and counter anions play important roles in deciding the resulting architectures [11,12,13]
We have elaborately designed the series of 4-imidazole-containing imidazole ligands such as 1,4-di(1H-imidazol-4-yl)benzene and 1,3,5-tri(1H-imidazol-4-yl)benzene and successfully synthesized the porous MOFs based on the metal-imidazolate building units, showing favorable gas adsorption, especially selective adsorption property for CO2 molecules [17,18]

Summary

Introduction

Rational design and successful construction of metal-organic frameworks (MOFs) has become an expanding research topic in the fields of synthetic chemistry and materials science because of their intriguing variety of architectures and captivating topologies and their potentially multi-field applications in numerous areas in fluorescence, gas adsorption/separation, magnetic properties, electrochemistry, catalysis, and so on [1,2,3,4,5,6,7,8]. The N-donor compounds such as imidazole, pyrazole, triazole, and tetrazole can exhibit flexible coordination modes and afford more predictable coordination modes, as a result, these types of ligands have been extensively employed to construct diverse complexes. Considering that a mixed ligand assembly strategy incorporating imidazole-containing ligands and polycarboxylates can effectively construct diverse topological networks, we have employed the We have elaborately designed the series of 4-imidazole-containing imidazole ligands such as 1,4-di(1H-imidazol-4-yl)benzene and 1,3,5-tri(1H-imidazol-4-yl)benzene and successfully synthesized the porous MOFs based on the metal-imidazolate building units, showing favorable gas adsorption, especially selective adsorption property for CO2 molecules [17,18].

Results

Discussion

Conclusion