Cyanide vs. azide “magnetic arm wrestling”: MnII–NbIV and MnII–MoIV magnetic coordination polymers with mixed bridging

Abstract

Two magnetic coordination polymers with mixed cyanide–azide bridging based on octacyanoniobate(IV) and octacyanomolybdate(IV) are reported: {(NH₄)[(H₂O)Mn^II-(μ-N₃)-Mn^II(H₂O)][M^IV(CN)₈]·3H₂O}_n Mn₂MN₃ (M = Nb or Mo). Cyanide ligands form the 3-D framework of Mn₂MN₃, while azide ligands connect two Mn^II centres together. Both CN⁻ and N₃⁻ are known in magnetochemistry for their marked magnetic coupling abilities which in the case of Mn₂NbN₃ lead to competitive antiferromagnetic interactions within the Nb^IV–CN–Mn^II and Mn^II–N₃–Mn^II structural motifs. This competition results in a peculiar magnetic behaviour consistent with a non-collinear magnetic structure.