Four 3D coordination polymers based on layers with single syn - anti carboxylate bridges: synthesis, structures, and magnetic properties.

Four novel coordination polymers (CPs) based on a new 4-(3,5-dicarboxylphenyl) picolinic acid ligands (H 3 L), [M 3 (L) 2 (H 2 O) 6 ]·4H 2 O (M 3 = Mn 3 , 1; Co 3 , 2; Ni 3 , 3, Co 1.01 Ni 1.99 , 4), have been hydrothermally synthesized, and structurally and magnetically characterized. In these isomorphous CPs, octahedrally coordinated metal ions are linked by the single syn - anti carboxylate bridge (μ-COO) to give linear trinuclear motifs. The motifs are connected through the other single syn - anti carboxylate bridge (μ-COO) to give a 2D (4,4) layer, and the layers are interlinked by the L ligands into 3D frameworks. Magnetic measurement indicates that antiferromagnetic interactions between metal ions are mediated through the single syn - anti carboxylate bridges in 1 and 2, while the same carboxylate bridges in 3 transmit ferromagnetic couplings. The bimetallic CP 4 shows interesting complicated magnetic behaviors due to the competition effect of Co(ii) and Ni(ii) ions.