Carefully selected molecular bridging ligands formate, cyanide and azide, that are known to transmit strong magnetic interactions, have been successfully inserted into the {[MnII(H2O)2]2[NbIV(CN)8]·4H2O}n (Mn2Nb) ferrimagnetic parent framework, resulting in the additional molecular bridging of the two MnII centres in three new coordination polymers: {(NH4)[(H2O)MnII-(μ-HCOO)-MnII(H2O)][NbIV(CN)8]·3H2O}nMn2NbHCOO, {(NH4)[(NH3)MnII-(μ-CN)-MnII(H2O)][NbIV(CN)8]·2H2O}nMn2NbCN and {(NH4)[(H2O)MnII-(μ-N3)-MnII(H2O)][NbIV(CN)8]·3H2O}nMn2NbN3. The extra bridging ligands cross-linking the two MnII centers strongly influence the long-range ferrimagnetic order of the NbIV-CN-MnII parent framework by introducing competing antiferromagnetic interactions. The values of the JMnMn constants were obtained by fitting the magnetic properties of the MoIV congeners {(NH4)[(H2O)MnII-(μ-HCOO)-MnII(H2O)][MoIV(CN)8]·3H2O}nMn2MoHCOO, {(NH4)[(NH3)MnII-(μ-CN)-MnII(H2O)][MoIV(CN)8]·2H2O}nMn2MoCN and {(NH4)[(H2O)MnII-(μ-N3)-MnII(H2O)][MoIV(CN)8]·3H2O}nMn2MoN3, where the paramagnetic NbIV was substituted by the diamagnetic MoIV, thus disabling the long-range magnetic ordering of the CN-framework. Our strategy demonstrates how chemists can control the magnetic behavior of molecular magnets by subtle and rational structural modification based on chemical knowledge.