Synthesis, structural characterization and magnetic properties of polymeric azido Mn(II) complexes based on methyl-pyridine-N-oxide co-ligands

Abstract

Three different coordination polymeric compounds have been synthesized and structurally characterized in the reaction of aqueous solution of Mn(NO3)2·4H2O with methylpyridine-N-oxide co-ligands (Mepy-N-oxide) in the presence of NaN3 depending on the position of the methyl group in Mepy-N-oxide namely: [Mn(μ(O,O)-2-Mepy-N-oxide)(μ1,3-N3)2]n (1), catena-{[Mn(μ1,1-N3)2(H2O)2](3-Mepy-N-oxide)2} (2) and [Mn3(μ1,1-N3)2(μ1,3-N3)4(μ(O,O)-4-Mepy-N-oxide)2(H2O)2]n (3). Single crystal X-ray crystallography revealed the polymeric nature of the complexes as 2D, 1D and 3D networks, respectively with a doubly end-to-end (EE) azide bridging and μ(O,O) bridging 2-Mepy-N-oxide in 1, and a doubly end-on (EO) azide bridging in 2. In complex 3 within the trinuclear subunit the three Mn(II) atoms are bridged via EO azido groups and μ(O,O) bridging 4-Mepy-N-oxide molecules and the trinuclear subunits are connected further by EE azido bridges to generate the 3D network structure. The magnetic properties of the three complexes were investigated over the temperature range 2–300K. Complex 2, as far as we know, is the first Mn(II) uniform 1D compound with double EO azido bridges which shows antiferromagnetic coupling. The fit of the magnetic data by using the appropriate equation derived from the Hamiltonian H=−∑JSi·Si+1 gives the best fit parameters J=−3.55(1)cm−1, g=2.044(1).