ZnII Complexes Based on Hybrid N-Pyrazole, N′-imine Ligands: Synthesis, X-Ray Crystal Structure, NMR Characterisation, and 3D Supramolecular Properties

Abstract

The present report is on the synthesis of two new 3-imine-3,5-dimethylpyrazole ligands, N-[3-(3,5-dimethyl-1H-pyrazol-1-yl)propylidene]ethylamine (L1) and N-[3-(3,5-dimethyl-1H-pyrazol-1-yl)propylidene]propylamine (L2). These ligands form molecular complexes with the formula [ZnCl2(L)] (L = L1 (1) and L2 (2)) when the reacting with ZnCl2 in a metal (M)/ligand (L) ratio of 1 : 1. These new ZnII complexes have been characterised by elemental analyses, conductivity measurements, mass spectrometry, and infrared, 1H and 13C{1H} NMR spectroscopy techniques. The two crystalline structures of complexes 1 and 2 have been solved by X-ray diffraction methods. Finally, we have studied the self-assembly three-dimensional supramolecular structure through different intra- and intermolecular contacts. The application of these ZnII complexes in supramolecular crystal engineering is interesting due to (1) the easy preparation and the high efficiency of this system and (2) the different bonding properties of the heteroatoms (N-pyrazole vs N-imine) present in the structure of the ligands.