Chelating Schiff base assisted azide-bridged Mn(ii), Ni(ii) and Cu(ii) magnetic coordination polymers

Abstract

Four new Mn(II), Ni(II) and Cu(II) coordination polymers [Mn₂(L¹)(μ_1,1-N₃)₂(μ_1,3-N₃)₂]_n (1), [Ni(L²)₂(μ_1,3-N₃)]_n(ClO₄)_n (2), [Cu(L³)(μ_1,1-N₃)(N₃)]_n (3) and [Cu(L⁴)(μ_1,1-N₃)₂]_n (4) (L¹ = N,N′-bis(2-pyridylmethylene)ethane-1,2-diamine, L² = N-(2-pyridylmethylene)methylamine, L³ = N-(2-pyridylmethylene)-3-pyridylamine, L⁴ = N-(2-pyridylmethylene)-^tbutylamine) have been synthesized and characterized by single-crystal X-ray analysis and magnetic measurements. Complex 1 indicates a stoichiometry-dependent structural change (based on Mn : L¹ : N₃ = 2 : 1 : 4 molar ratio) and consists of two-dimensional (2-D) (4,4) net layers, in which Mn(II) centers are co-bridged by single end-to-end (EE), double end-on (EO) azide and chelate-bridging L¹ ligands. Complex 2 shows a single EE azide-bridged one-dimensional (1-D) Ni(II) chain. Complexes 3 and 4 indicate single EO and double EO azide-bridged 1-D Cu(II) chains, respectively. Complex 1 exhibits weak ferromagnetism due to its intra-layer spin-canting with T_c = 20 K. Complex 2 shows an unusual intra-chain ferromagnetic coupling and spin-canting behaviour. Both complexes 3 and 4 exhibit intra-chain antiferromagnetic interactions. Magneto-structural parameters for these related complexes were also discussed.