New Bis-Pyrazole-Bis-Acetate Based Coordination Complexes: Influence of Counter-Anions and Metal Ions on the Supramolecular Structures

Afaf Oulmidi,Haralampos N Miras,Yann Garcia,Nayarassery N Adarsh,Smaail Radi

doi:10.3390/su13010288

Abstract

A new flexible bis-pyrazol-bis-acetate ligand, diethyl 2,2’-(pyridine-2,6-diylbis (5-methyl-1H-pyrazole-3,1-diyl))diacetate (L), has been synthesised, and three coordination complexes, namely, [Zn(L)2](BF4)2 (1), [MnLCl2] (2) and [CdLCl2] (3) have been obtained. All ligands and complexes were characterised by IR, mass spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. Single crystal X-ray diffraction experiment revealed that the primary supramolecular building block of 1 is a hexagonal chair shaped 0D hydrogen bonded synthon (stabilised by C–H∙∙∙O hydrogen bonding and C=O∙∙∙π interactions), which further built into a 2D corrugated sheet-like architecture having a 3-c net honeycomb topology, and finally extended to a 3D hydrogen bonded network structure having a five nodal 1,3,3,3,7-c net, through C–H∙∙∙F interactions. On the other hand, the two crystallographically independent molecules of 2 exhibited two distinct supramolecular structures such as 2D hydrogen bonded sheet structure and 1D zigzag hydrogen bonded chain, sustained by C–H∙O and C–H∙∙∙Cl interactions, which are further self-assembled into a 3,4-c network structure, and 3 showed a 2D hydrogen bonded sheet structure. The supramolecular structural diversity in these complexes is due to the different conformations adopted by the ligands, which are mainly induced by different metal ions with coordination environments controlled by different anions. Hirshfeld surface analysis was explored for the qualitative and quantitative analysis of the supramolecular interactions.

Highlights

Introduction nal affiliationsDesigning coordination complexes by using supramolecular self-assembly is an important research area in materials chemistry [1]
We have demonstrated the effect of account, we have studied the effect of anions and hydrogen bonding on the supramolecthe aliphatic backbone of the bis-pyrazole-bis-carboxylate ligand on the supramolecular ular structural diversities of Cu(II) and Mn(II) coordination complexes obtained from a structures of their Co(II)/Cu(II)/Cd(II) coordination complexes [17]
For completeness, MnCl2∙4H2O and CdCl2∙2.5H2O in a 1:2 molar ratio, which led to single crystals which were systematically investigated by single crystals X-ray diffraction (Scheme 2)

Summary

Introduction

Introduction nal affiliationsDesigning coordination complexes by using supramolecular self-assembly is an important research area in materials chemistry [1]. The use of relatively simple organic ligands and metal ions through their kinetically labile and thermodynamically stable coordination bonds attracted many research groups due to their various potential applications [2,3,4,5,6,7]. Such self-assembly resulted in channels or void spaces, wherein host-guest chemistry played a role for the incorporation of small molecules or anions within such empty spaces [8]. Ligands having two hetero nitrogen atoms such as imidazole [12], pyrazole [13,14] and pyrazine [15] are not much explored in the coordination chemistry of transition metals.

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