Hydrogencyanamido bridged multinuclear copper(ii) complexes: From strong antiferromagnetic couplings to weak ferromagnetic couplings

摘要

In the presence of ammonia, the reactions of cyanamide and Cu~(II) ions with different organic blocking ligands afford three hydrogencyanamido bridged dinuclear complexes: [(dmbpy)_4Cu_2(HNCN)](ClO _4)_3·H_2O (1, dmbpy = 4,4′-dimethyl- 2,2′-bipyridine), [(phen)_4Cu_2(HNCN)](ClO _4)_3·2H_2O (2, phen = 1,10-phenanthroline) and [(bpy)_2Cu_2(HNCN)_2(ClO_4) _2] (3, bpy = 2,2′-bipyridine), respectively. However, using the di(2-pyridyl)ketone (dpk) ligand in similar experimental conditions, an interesting reaction between the hydrogencyanamido anion and dpk is observed. Using Cu(ClO_4)·6H_2O or Co(ClO_4) ·6H_2O as the metal source, it gives the mixed bridged hexanuclear complex [(dpk·OMe)_4(dpk·NCN) _2Cu_6(H_2O)_2](ClO_4) _4 (4), or the mononuclear complex [(dpk·OMe)(dpk·HNCN) Co](ClO_4)·2H_2O (5), respectively. Their structures are characterized by single crystal X-ray diffraction analyses. Magnetic measurements reveal moderate antiferromagnetic interaction between the Cu II ions in complex 1, weak ferromagnetic coupling in complex 2, and strong antiferromagnetic interactions for complexes 3 and 4. The magnetostructural correlations of these complexes are discussed.