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

The reactions of Mn<sup>II</sup> ions with azido ligands in the presence of nicotinic/isonicotinic acids gave two manganese(II) azido coordination polymers, [Mn<sub>3</sub>(<b>L</b><sup><b>1</b></sup>)<sub>2</sub>(N<sub>3</sub>)<sub>4</sub>]<sub><i>n</i></sub>·<i>n</i>H<sub>2</sub>O (<b>1</b>) and [Mn<sub>2</sub>(<b>L</b><sup><b>2</b></sup>)(N<sub>3</sub>)<sub>3</sub>]<sub><i>n</i></sub> (<b>2</b>), where <b>L</b><sup><b>1</b></sup> = nicotinate and <b>L</b><sup><b>2</b></sup> = isonicotinate, with different topological structures. Complex <b>1</b> consists of 2D azido−Mn<sup>II</sup> planes, which is further linked by <b>L<sup>1</sup></b> to form a 3D framework with unprecedented 3,6-connected 4-nodal net topology, and complex <b>2</b> presents an unprecedented 3,4,6-connected 6-nodal 3D azido−Mn<sup>II</sup> structure with <b>L<sup>2</sup></b> as the coligand. Magnetic susceptibility measurements reveal dominant antiferromagnetic coupling existing in <b>1</b> and <b>2</b>. Complex <b>1</b> 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 <b>2</b> is an antiferromagnet and exhibits field-induced spin-flop behavior.