Rational design of manganese-micro-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(micro(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(micro(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 pi-pi-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 chiM or chiMTvs.T for can be fitted as a homogeneous 2D system with J=-5.4 cm(-1), g=2.05. Also, at high temperatures the plots of chiM or chiMTvs.T for compound can be fitted with the simple cubic expansion series with J=-1.6 cm(-1), g=2.04. Compound 1 shows spontaneous magnetization below Tc=45 K, which corresponds to the presence of spin-canted antiferromagnetism, whereas 2 and 3 do not show spontaneous magnetization up to 2 K.