Synthesis, crystal structure and magnetic properties of new copper(II) complexes based on 3-(2-pyridyl)-1,2,4-triazole

The synthesis, crystal structure, spectroscopic and magnetic properties of binuclear [Cu-2(L)(2)(SO4)(H2O)(3)]center dot 3H(2)O (4a) and tetranuclear [Cu-4(HL)(2)(L)(4)(DMF)(2)(SO4)(2)]center dot DMF (4b) copper(II) complexes were reported (where HL is 3-(pyridine-2-yl)-1,2,4-triazole). Potentiometric titrations, ESI-MS and spectrophotometric studies of complex formation in MeOH/H2O solutions indicated the presence of monomeric [CuHL](2+), dinuclear [Cu2L2](2+) and [Cu2L2(OH)](+), and trinuclear [Cu2L3](+) and [Cu2L3(OH)] species. The small N,N-nucleating ligand HL leads to a supramolecular formation of the complexes. The ligand comprises a triazole moiety substituted by pyridine group, strategically located to form chelate metalocycles. The basis of both complexes is two metal centres bridged via N-1-N-2 diazine grouping of a triazole ring. For complex 4b two HL coordinate in acidoform via N-Py and N-4 of azole moiety as well. There are significant differences in the polyhedrons, namely nuclearity and Cu...Cu separations. Complexes were characterized by elemental analysis, mass-spectrometry, IR- spectroscopy and X-ray analysis. Magnetic measurements revealed that both compounds exhibit antiferromagnetic interaction. The magnetic susceptibility data were interpreted on the basis of the spin Hamiltonian in the temperature range (2-300 K) using the dinuclear (4a: J(1) = -52.41 cm(-1)) and tetranuclear (4b: J(1) = -53.10 cm(-1) to J(2) = -0.14 cm(-1)) models.