Copper(II), Nickel(II), and Cobalt(II)/(III) Self-Assembled Polynuclear Complexes of Bis[(pyridin-2-yl)-1,2,4-triazol-3-yl]]methane

The reactions of bis[(pyridin-2-yl)-1,2,4-triazol-3-yl]methane (H2L) with copper(II), nickel(II), and cobalt(II) salts afford a series of unusual structures; among them are the homoleptic binuclear complexes [Ni-2(H2L)(2)(H2O)(4)](NO3)(4) center dot 6H(2)O (1) and [Ni-2(H2L)(2)Cl-2]Cl-2 center dot 4H(2)O center dot 2C(4)H(8)O(2) (2), the octanuclear complex [Ni-8(H2L)(12)](NO3)(16) center dot 21H(2)O (3), and the tetranuclear complexes [Cu-4(HL)(4)](ClO4)(4) center dot C2H5OH center dot 3H(2)O (4), [Co-4(HL)(2)(H2L)(2)(H2O)(4)](NO3)(8) center dot C2H5OH center dot 6H(2)O (5), and [Co-4(HL)(2)(H2L)(2)(H2O)(4)] center dot(ClO4)(8) center dot 8H(2)O (6). All these compounds have been characterized by different techniques, such as elemental analysis, electrospray mass spectrometry (ES-MS), UV/Vis spectroscopy, X-ray structural analyses, and magnetic measurements. It was found that the nature of the cation and the metal/ligand ratio have a substantial impact on the coordination geometries of the unique complexes. The magnetic properties of compounds 1 and 2 show the presence of intramolecular ferromagnetic exchange interactions (J = +2.3 and +15.2 cm(-1)) combined with intermolecular antiferromagnetic coupling. Complexes 3, 5, and 6 show weak intramolecular antiferromagnetic interactions, while complex 4 shows quite strong antiferromagnetic behavior (J = 53.7 cm(-1)).