Ferromagnetic interactions through double hydrogen bonding bridges in manganese(ii) coordination polymers

Three isostructural Mn(ii) compounds with a zwitterionic dicarboxylate ligand and different pseudohalides were synthesized, and then structurally and magnetically characterized. They are formulated as [Mn(L)(X)₂(H ₂O)₂]_n [X = N₃^- (1), NCO^- (2), NCS^- (3), L = 1,4-bis(4-carboxylato-1- pyridinium)butane]. In these compounds, adjacent Mn(ii) ions are connected into coordination chains by long zwitterionic linkers and into hydrogen-bonded chains by short double O-H⋯N bridges involving coordinated water and pseudohalide ligands. Magnetic studies revealed for the first time that the double hydrogen bridges induce ferromagnetic coupling between the Mn(ii) ions.