MnII, CuII and CoII coordination polymers showing antiferromagnetism, and the coexistence of spin frustration and long range magnetic ordering

Based on the ligand 1,2-H2bdc (1,2-H2bdc = 1,2-benzenedicarboxylic acid), three 2D coordination polymers [Mn(1,2-bdc)]n (1), [Cu(1,2-bdc)]n (2) and [Co3(OH)2(1,2-bdc)2]n (3), have been prepared and characterized. In comparison with the mononuclear Mn unit of compound 1, paddle-wheel binuclear Cu2(CO2)4 and trinuclear Co3(OH) building units are observed in 2 and 3, respectively. Also, the bdc2− ligands adopt different coordination modes in the three compounds. The resulting two frustrated lattices have been observed, such as the triangular lattice for 2 and the Kagomé lattice for 3, and thus, both complexes 2 and 3 show spin frustrated antiferromagnetic properties. In addition, the magnetic hysteresis loops reveal the existence of the long range ordering in 2 and 3. Comparatively, the magnetic measurements indicate that compound 1 exhibits a weak antiferromagnetic interaction, and the fit of the variable-temperature magnetic susceptibility data to the empirical equation leads to the following parameters: J = −0.80(1) cm−1 and g = 2.02.