Cyanide vs. azide "magnetic arm wrestling": Mn II -Nb IV and Mn II -Mo IV 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 )[(H2 O)MnII -(μ-N3 )-MnII (H2 O)][MIV (CN)8 ]·3H2 O}n Mn2 MN3 (M = Nb or Mo). Cyanide ligands form the 3-D framework of Mn2 MN3 , while azide ligands connect two MnII 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 NbIV -CN-MnII and MnII -N3 -MnII structural motifs. This competition results in a peculiar magnetic behaviour consistent with a non-collinear magnetic structure.