New Manganese(II) Azido Coordination Polymers with Nicotinic/Isonicotinic Acids as Coligands: Synthesis, Structure, and Magnetic Properties

The reactions of Mn-II ions with azido ligands in the presence of nicotinic/isonicotinic acids gave two manganese(II) azido coordination polymers, [Mn-3(L-1)(2)(N-3)(4)](n) center dot nH(2)O (1) and [Mn-2(L-2)(N-3)(3)](n) (2), where L-1 = nicotinate and L-2 = isonicotinate, with different topological structures. Complex 1 consists of 2D azido-Mn-II planes, which is further linked by L-1 to form a 3D framework with unprecedented 3,6-connected 4-nodal net topology, and complex 2 presents an unprecedented 3,4,6-connected 6-nodal 3D azido-Mn-II structure with L-2 as the coligand. Magnetic susceptibility measurements reveal dominant antiferromagnetic coupling existing in 1 and 2. Complex 1 is a spin-competitive system and enters into a weak ferromagnetic-to-magnetic phase transition at the critical temperature of 6 K due to spin canting. Complex 2 is an antiferromagnet and exhibits field-induced spin-flop behavior.