Effect of Different Synthesis Approaches on Structural and Thermal Properties of Lanthanide(III) Metal\u2013Organic Frameworks Based on the 1H-Pyrazole-3,5-Dicarboxylate Linker

Dmytro Vlasyuk,Renata Łyszczek

doi:10.1007/s10904-021-02018-w

Abstract

The impact of different synthetic procedures such as: hydrothermal, mechanochemical and precipitation on the structure and thermal properties of coordination polymers of 1H-pyrazole-3,5-dicarboxylic acid (H3pdca) with selected lanthanide ions was determined. The prepared complexes of the general formula: Ln2(Hpdca)3⋅nH2O, where Ln = Eu(III), Nd(III), Tb(III) and Er(III); n = 6 or 7 were fully investigated by: elemental analysis, Energy-Dispersive X-Ray (ED-XRF) and infrared (ATR-FTIR) spectroscopy, powder as well as single-crystal X-ray diffraction methods and thermal analysis (TG-DSC and TG-FTIR) in various atmospheres. It was proved that all used strategies offer high yields of reactions along with crystallinity of the obtained products. The X-ray diffraction methods allowed to conclude that the complexes with the same metal ions exhibit the same crystal structure despite different synthesis routes. On the other hand, the coordination polymers of Eu(III), Tb(III) and Er(III) prepared under different conditions are isomorphous. Only neodymium(III) compounds have a different crystal structure. Thermal stability of the produced complexes was correlated with the synthesis conditions, in particular with the way of energy supply. It was found that the highest thermal stability was exhibited by the complexes prepared under the hydrothermal conditions. Additionally, based on the volatile products of metal complexes decomposition, the mechanism of their pyrolysis was proposed in relation to their structures.

Highlights

Coordination polymers (CPs) have been regarded as a new group of multifunctional materials due to their intriguing physicochemical properties resulting from the combination of inorganic and organic building blocks
This paper presents our results concerning lanthanide coordination polymers obtained by different processing like hydrothermal, mechanochemical and classical precipitation procedures
Besides the hydrothermal method (HT), which is commonly used in the synthesis of coordination polymers, mechanochemical (Mech) and classical precipitation approaches (Prep) were applied

Summary

Introduction

Coordination polymers (CPs) have been regarded as a new group of multifunctional materials due to their intriguing physicochemical properties resulting from the combination of inorganic and organic building blocks. Of metal ions or metal clusters with the bridging organic ligands resulted in the formation of “infinite” metal–ligand polymeric structures of different dimensionalities [1,2,3,4,5]. Journal of Inorganic and Organometallic Polymers and Materials (2021) 31:3534–3548 is the selection of an organic ligand with the appropriate functional groups which will be able to coordinate metal centers and form bridges among them. The presence of additional binding sites allows creating additional strong covalent bonds with metal ions resulting in the formation of novel extraordinary architectures with desired structural properties. Taking into account the fact that the metal–organic frameworks are mainly considered as porous materials, such structural elements enhance compounds functionality [41, 42]

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Results

Conclusion