Magnetic properties of dinuclear copper(II) complexes with simple pyrazolate bridges

Abstract

Three new copper(II) complexes with simple pyrazolate bridges have been prepared, [Cu₂(pz)₂(dpa)₂(H₂O)Cl]Cl·H₂O 1, [Cu₂(pz)₂(phen)₂Cl₂]·2C₂H₅OH 2 and [Cu₂(pz)(phen)₂Cl₃]·2H₂O 3 (Hpz = pyrazole, dpa = di(2-pyridyl)amine, phen = 1,10-phenanthroline) and their crystal and molecular structures determined. The copper centres in the binuclear cation in 1 have a square pyramidal geometry at Cu1 and a distorted octahedral geometry at Cu2. The neutral complexes 2 and 3 have the copper atoms in a distorted square pyramidal geometry. Complexes 1 and 2 are bibridged by pyrazolate while 3 is monobridged by this ligand. Variable temperature magnetic studies on all three complexes indicate the existence of antiferromagnetic exchange phenomena (–2J = 191, 169, 42 cm^–1 for 1, 2 and 3 respectively). Extended Hückel calculations showed a HOMO/LUMO gap which is in agreement with the experimental data.