Structural and magnetic characterization of Ni(ii), Co(ii), and Fe(ii) binuclear complexes on a bis(pyridyl-triazolyl)alkane basis

Abstract

Reactions of bis[5-(2-pyridyl)-1,2,4-triazol-3-yl]alkanes (alkane spacers = –CH₂– in L2, –C₃H₆– in L3, –C₄H₈– in L4) with M(II)A₂ salts (M = Ni, Co, Fe) resulted in the preparation of five series of mononuclear ([M(L2)(H₂O)₂]²⁺, 1a–c) or binuclear ([M₂(L3)₂(H₂O)₄]⁴⁺, 2a–c; ([M₂(L4)₂(H₂O)₄]⁴⁺, 3a–c, [M₂(L3)₂(μ-ox)]²⁺, 4a–c; [M₂(L4)₂(μ-ox)]²⁺, 5a–c) complexes. The crystal structures of ten complexes were determined by single-crystal X-ray crystallography. Magnetic properties of the compounds were characterized by SQUID magnetometry and were analyzed by fitting on a spin Hamiltonian model. It was revealed that Fe(II) and Co(II) compounds exhibit non-negligible anisotropy and in the case of 2a–c and 3a–c complexes weak ferromagnetic interactions between the metal centers were observed. In the case of complexes containing an {M₂(μ-ox)}²⁺ core strong antiferromagnetic interactions were observed within the dimer. Remarkably, solid state luminescence of Co(II) and Fe(II) complexes (1b, 2b, 3b and 1c, 2c, 3c) was observed.