Tuning the Crystal Structure Dimensionality of Cobalt(II)/1,2,4-Triazole Complexes

To control the structure dimensionality of hybrid materials, a common approach consists of selecting ligands with specific bridging modes. Herein, we show that the bridging mode for some azole ligands with Co(II) metal ions can be tuned in situ using different synthesis conditions. For example, the dimensionality of 1,2,4-triazole based materials could be controlled according to their (de)protonation. Under hydrothermal conditions, deprotonation commonly occurs and leads to the tripodal moiety that favors a high dimensional crystal structure. To target low -dimensional 1,2,4-triazole based cobalt materials, deprotonation was prevented by carrying out hydrothermal syntheses under strong acidic conditions. With this strategy, two new compounds with low dimensional crystal structures were obtained: Co(Htrz)Cl-2 (1) exhibiting onedimensional coordination polymers and [Co-3(Htrz)(6)(H2O)(6)][ZnBr4](3)center dot 9H(2)O (2) containing Co trinudear complexes (Htrz = 1,2,4-triazole). Magnetic measurements showed weak antiferromagnetic interactions between Co(II) centers in both systems.