Four 3,5-diamino-1,2,4-triazole-based cobalt(II/III) complexes incorporating with 5-substituted isophthalate coligands: Synthesis, structure and magnetism

Four 3,5-diamino-1,2,4-triazole (Hdatrz)-based cobalt(II/III) coordination polymers, {[Co2(Hdatrz)(NH2-ip)2]·0.5H2O}n (1), [Co(CH3OH)(Hdatrz)(CH3-ip)]n (2), {[Co2(datrz)2(CH3-ip)]·2.5H2O}n (3) and {[Co(datrz)(NO2-ip)]·H2O}n (4) (NH2-ip2− = 5-aminoisophthalate, CH3-ip2− = 5-methylisophthalate and NO2-ip2− = 5-nitroisophthalate), were hydro-/solvothermally synthesized by changing the substituents attached on the isophthalate coligand, which were structurally and magnetically characterized. Complex 1 is a corrugated layer with dimeric {Co2(μ-N1,N2-Hdatrz)}4+ subunits extended by three-connected NH2-ip2− connectors. Constructed from the same mixed ligands, both 2 and 3 exhibit robust three-dimensional (3D) frameworks consisting of helical {Co(μ-N1,N4-Hdatrz)}2+ chain and corner-sharing triangular {Co2(μ3-N1,N2,N4-datrz)2}2+ layer, respectively. By contrast, two bis-monodentate NO2-ip2− and two μ-N1,N4-datrz− anions connect tetrahedral Co(III) sites into a (4, 4) grid-like layer of 4. Thus, the substituent of the isophthalate coligand is observed to virtually influence the overall structures of the resulting complexes by changing the binding modes of the coligand and coordination polyhedra. Additionally, complex 1 exhibits a metamagnetic transition from antiferromagnetic ordering to weak ferromagnetic state. Instead, typically antiferromagnetic interactions are respectively mediated by the cyclic triazolate ligand along the helical chain of 2 and in the distorted triangular layer of 3.

Four coordination polymers with binuclear subunit, helical chain, distorted triangular and (4, 4) topological layer were generated by varying the substituent of isophthalate in the ternary CoII-3,5-diamino-1,2,4-triazolate-isophthalate system. Three of them exhibit metamagnetic transition and typically antiferromagnetic interactions.Figure optionsDownload as PowerPoint slide