Three novel 3,5-diamino-1,2,4-triazole (Hdatrz)-based Co(II) coordination complexes, [Co(Hdatrz)(0.5)(H(2)O)(2)(btec)(0.5)](n) (1), {[Co(Hdatrz)(Hbtc)]·H(2)O}(n) (2) and [Co(2)(datrz)(2)(nb)(2)](n) (3) (H(4)btec = 1,2,4,5-benzenetetracarboxylic acid, H(3)btc = 1,3,5-benzenetricarboxylic acid and Hnb = 4-nitrobenzoic acid), were synthesized by incorporating different carboxylate-containing co-ligands and then were structurally and magnetically characterized. Complex 1 is a 3D pillared-layer framework with corrugated Co(II)-btec(4-) layers supported by neutral μ(2)-N1, N4-Hdatrz ligands. In contrast, the other two complexes are chiral (4, 4)- and racemic (4, 8(2))-topological layers with asymmetric μ(2)-N1, N4-Hdatrz-bridged helical chains extended by bis-monodentate Hbtc(2-) ligands for 2 and with a μ(3)-N1, N2, N4-datrz((-)) aggregated Shastry-Sutherland magnetic layer for 3. More interestingly, different magnetic phenomena with a field-induced metamagnetic transition from antiferromagnetic ordering to a ferromagnetic state for 1, spin-canted antiferromagnetism with a T(N) lower than 2.0 K for 2, as well as the coexistence of spin frustration and spin-flop transitions for 3 were observed, which, significantly, are governed by the local low-dimensional magnetic motifs mediated by the carboxylate and/or triazolate heterobridges in the anisotropic Co(II)-triazolate system.
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