Cyanide vs. azide magnetic arm wrestling'': MnII-NbIV and MnII-MoIV magnetic coordination polymers with mixed bridging

Two magnetic coordination polymers with mixed cyanide-azide bridging based on octacyanoniobate(IV) and octacyanomolybdate(IV) are reported: {(NH4)[(H2O)Mn-II-(mu-N-3)-Mn-II(H2O)][M-IV(CN8]center dot 3H(2)O}(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 N-3(-) 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-N-3-Mn-II structural motifs. This competition results in a peculiar magnetic behaviour consistent with a non-collinear magnetic structure.