Synthesis, crystal structure and magnetism of three novel copper(II) complexes with pyrazole-based ligands

Abstract

► Monomeric copper(II) complex with pyrazole derivative ligands. ► The metal ions display cis and trans conformation depending on the ligand. ► A network of intermolecular interactions stabilizes the crystal packing. ► Magnetic measurements reveal weak antiferromagnetic interactions. In this work we present the synthesis, crystal structure and magnetic properties of three copper(II) pyrazole-based complexes. These compounds were prepared by reactions between the ligands ( L1 = 5-amino-1-phenyl-1 H -pyrazole-4-carbonitrile, L2 = 5-amino-1-(4’metoxiphenyl)-1 H -pyrazole-4-carbonitrile and L3 = Ethyl 5-amino-1-phenyl-1 H -pyrazole-4-carboxylate) and CuCl 2 ·2H 2 O using an appropriate solvent. The crystalline structures of [Cu(L1) 2 Cl 2 ] ( 1 ), [Cu(L2) 2 Cl 2 ] ( 2 ) and [Cu(L3) 2 Cl 2 ] ( 3 ) showed that copper ion is coordinated by two pirazolic ligands through pyridinic nitrogen atom and two chloride ions in a distorted square-planar geometry. The magnetic measurements revealed a paramagnetic behavior for ( 1 ) and weak antiferromagnetic coupling between copper(II) ions in ( 2 ) and ( 3 ). Due to the presence of labile chloride ions in the structures, these monomeric copper(II) complexes may be used as building blocks in the synthesis of molecular magnetic compounds.