A new nitrogen rich open chain diazine ligand system: synthesis coordination chemistry and magneto-structural studies

Abstract

The synthesis and coordination chemistry of a new series of open chain diazine based ligands (L_3aH₂, L_3bH₂, and L_3cH₂) is reported. The ligands comprise a central disubstituted bipyridine moiety with two bridging alkoxide oxygen donors, together with diazine and pyridine terminal groups strategically located to coordinate three metal centres. Reactions of L_3aH₂ and L_3bH₂ with CuX₂ (X⁻ = ClO₄, Cl, NO₃) yield a trinuclear complex (1) and 1-D copper chains (2, 3). In these complexes the ligands bind copper ions via N_bipyridne, trans N_diazine, O_hydrazone, and N_pyridne donors while vacant sites are occupied by counter ions or solvent molecules (methanol, water, acetonitrile). Reaction of L_3cH₂ with MnCl₂ affords a linear trinuclear Mn complex (4), where the Mn(II) ions are connected via μ₂-O_hydrazone linkers with no N–N bridging. Reaction of L_3aH₂ with Fe(SO₃CF₃)₂ yields a tetranuclear mixed valence Fe complex (5), in which both trans N–N and O_hydrazone bridging is observed. Magnetic studies reveal the presence of moderate to strong antiferromagnetic interactions in complexes 1–4 while a mix of ferromagnetic and antiferromagnetic interactions is observed in complex 5.