Structural Invariance of a ZnII Coordination Polymer with 5-Aminoisophthalic Acid under Different Synthetic Conditions

Iara Rosa,Carlos Pinheiro,Luana Giusto,Antonio Doriguetto,Ana Dos Santos

doi:10.21577/0103-5053.20170052

Abstract

A same coordination polymer [Zn(aip)(DMSO)] (aip: 5-aminoisophthalate and DMSO: dimethylsulfoxide) was synthesized using the same reactants (ZnSO4, aip and H2O/DMSO) but in different conditions, in which the stoichiometry (1:1-4:1 metal:ligand ratio), temperature (70 and 100 °C) and synthetic method (liquid-liquid diffusion, solvothermal and conventional with stirring) varied. A liquid assisted mechanochemical approach using ZnO as ZnII source instead ZnSO4, but keeping DMSO as milling liquid, also resulted in the same compound. This new coordination polymer was investigated using single-crystal X-ray diffraction technique, revealing a two-dimensional honeycomb-type network formation. The crystal structure was compared with either similar or isostructural compounds reported in the literature. Our studies show that the synthetic method and other synthetic variables do not affect the formation of [Zn(aip)(DMSO)] coordination polymers and probe the high stability (thermodynamic and kinetic) and structural invariance of this structure.

Highlights

The term coordination polymers (CPs) is used to describe a large and continuously growing class of polymeric compounds that comprise two parts: metal ions and ligands linked by covalent bonds, which extend into one (1D), two (2D) or three (3D) dimensions.[1]
The starter reactants constituted by ZnSO4 or ZnO as ZnII source, H2aip as ligand, and dimensional coordination polymer [Zn(aip) (DMSO) as solvent, were used here in a wide range of reaction conditions in order to investigate the influence of synthetic methods in the structure and dimensionality of CPs (Figure 1)
The work aimed to verify the influence of two synthetic method in the structure and dimensionality of CPs obtained from ZnII, H2aip and DMSO

Summary

Introduction

The term coordination polymers (CPs) is used to describe a large and continuously growing class of polymeric compounds that comprise two parts: metal ions (inorganic) and ligands (in most cases, organic) linked by covalent bonds, which extend into one (1D), two (2D) or three (3D) dimensions.[1] Amino carboxylic acid derivatives as 5-aminoisophthalic acid (H2aip or aip for its dianion species) (Scheme 1) are widely quoted in the literature as CP former.[2] H2aip has two carboxylate groups at the 1 and 3 positions that have been demonstrated as an excellent structure motif for constructing different secondary building unit (SBUs).[3] In addition, the amino group may affect the assembly process of CPs acting either as a new coordination site to bond with more metal centers or a hydrogen bond donor or acceptor to enhance the number of non-covalent interactions.[4]. The synthesis and structural characterization of CPs have continued to expand as areas of extremely active research. Chemical structure of the 5-aminoisophthalic acid (H2aip or aip in its deprotonated form)

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Conclusion