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

Abstract

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 [Ni2(H2L)2(H2O)4](NO3)4·6H2O (1) and [Ni2(H2L)2Cl2]Cl2·4H2O·2C4H8O2 (2), the octanuclear complex [Ni8(H2L)12](NO3)16·21H2O (3), and the tetranuclear complexes [Cu4(HL)4](ClO4)4·C2H5OH·3H2O (4), [Co4(HL)2(H2L)2(H2O)4](NO3)8·C2H5OH·6H2O (5), and [Co4(HL)2(H2L)2(H2O)4]·(ClO4)8·8H2O (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).