Rational design of manganese-μ-azido 3D compounds by using diazines as co-ligands: synthesis, structure and magnetic behaviour

Abstract

The syntheses, structural characterization, and magnetic behaviour of three new 3D manganese(II) complexes with the empirical formulae [Mn(N₃)₂(5-Brpym)]_n (1), [Mn(N₃)₂(Mepyz)]_n (2) and [Mn(N₃)₂(2-acpy)]_n (3), (5-Brpym = 5-bromopyrimidine, Mepyz = methylpyrazine, 2-acpy = 2-acetylpyridine), are reported. In 1, each manganese atom is linked to the four nearest neighbours by only end-to-end azido bridges, forming square layers. These layers are further connected to 3D networks by the N,N′-bridging ligand. In 2, Mn₂(μ_1,1-N₃)₂ subunits are connected to the four nearest neighbours by end-to-end azido bridges to form a 3D Mn-azido-sublattice. The Mn₂(μ_1,1-N₃)₂ subunits are further linked by pairs of N,N′-bridging Mepyz ligands to form 1D ribbons extended along the c-axis of the unit cell. The Mepyz pairs show π–π-interactions. In 3, the only end-to-end azido bridges form a diamondoid-like 3D Mn-azido-sublattice. The magnetic properties of 1–3 are reported. At high temperatures, the plots of χ_M or χ_MTvs.T for 1 can be fitted as a homogeneous 2D system with J = −5.4 cm⁻¹, g = 2.05. Also, at high temperatures the plots of χ_M or χ_MTvs.T for compound 3 can be fitted with the simple cubic expansion series with J = −1.6 cm⁻¹, g = 2.04. Compound 1 shows spontaneous magnetization below T_c = 45 K, which corresponds to the presence of spin-canted antiferromagnetism, whereas 2 and 3 do not show spontaneous magnetization up to 2 K.