Synthesis, spectral characterization and structural investigation on some 4-aminoantipyrine containing Schiff base Cu(II) complexes and their molecular association

Compounds [Cu(L1)2] (1) and [Cu(L2)2] (2), where L1 and L2 are Schiff base ligands of 4-aminoantipyrine and substituted salicylaldehydes, were synthesized and characterized using various spectroscopic techniques such as elemental analysis, UV–Vis, IR, and NMR. The single crystal X-ray structures for L1, L2, and their corresponding Cu(II) complexes assembled in a 1:2 metal to ligand ratio were analyzed for their various weak H-bonding and dimeric association. The structural analysis of compounds 1 and 2, being the first crystal structures in this series, deserves special attention to help further the understanding in this area of structure–reactivity correlation studies. Further these compounds, composed of very similar chemical composition with a small difference in the substituent on the salicylaldehyde moiety, influenced through various weak inter- and intramolecular H-bonding and C–H⋯π interactions, rearrange the geometry around Cu(II) from a tetrahedrally distorted square planar geometry in [Cu(L1)2] (1) to square planar in [Cu(L2)2] (2). Steric strain imposed by the methyl substitution on the 4-aminoantipyrine moiety of the Schiff base ligand, causing this small change of the Cu(II) geometry, along with various weak interactions is analyzed in detail.

Two important antipyrine Schiff base ligands and their Cu(II) complexes have been synthesized and characterized. The single crystal X-ray structures of 1 and 2, being the first in the series of this type of compound, explored that the mode of weak H-bonding interactions and steric effect profoundly influenced the Cu(II) geometry in 1 and 2, rearranging from a tetrahedrally distorted square planar geometry into a distorted square planar geometry.Figure optionsDownload as PowerPoint slide