Three 3-Amino-1, 2, 4-Triazole-Based Magnetic Complexes Incorporated with Different Carboxylate-Containing Coligands: Synthesis, Structures, and Magnetic Properties

Three 3-amino-1, 2, 4-triazole (atz)-based paramagnetic complexes, [Mn(atz)(pa)]n (1), {[Mn(atz)1.5(hip)]center dot H2O}n (2), and [Mn(H2O)2(atz)2(nb)2] (3) (H2pa = o-phthalic acid, H2hip = 5-hydroxylisophthalic acid, and Hnb = p-nitrobenzoic acid) were prepared by introducing different carboxylate-containing aromatic coligands, and structurally and magnetically characterized. Helical MnII-atz and bent MnII-pa2 chains are crosslinked by sharing the same metal sites to generate a honeycomb-shaped framework of 1. The undulated MnII-atz layers constructed from 22-member metallomacrocycles are periodically supported by ditopic hip2 ligands to lead to a pillared-layer structure of 2. In contrast, complex 3 is a centrosymmetric mononuclear entity, which is assembled into a three-dimensional supramolecular network by abundant hydrogen-bonding interactions. The structural difference of 13 is significantly due to the combinations of the flexible coordination modes adopted by the mixed atz and carboxylate groups. Weak and comparable antiferromagnetic couplings are observed in the nearest neighbors of 13, which are cooperatively transmitted either by short carboxylate and/or atz heterobridges or by weak non-covalent interactions.