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).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.