Synthesis, Structures, and Magnetic Properties of Three 3D Coordination Polymers Based on M4O4 Cubanes (M = MnII, FeII, CoII)

Three new isostructural coordination polymers, namely, [M4(mu 3-OMe)4(nic)4]n [M = MnII (1), FeII (2), and CoII (3); Hnic = nicotinic acid], have been solvothermally synthesized and magnetically characterized. Single-crystal X-ray diffraction study reveals that compounds 13 are three-dimensional frameworks, which are constructed through {M4(mu 3-OMe)4} cubane-like building blocks and bridging nic anions. Variable-temperature magnetic susceptibility measurements indicate that they all show antiferromagnetic behavior with different intracubane coupling constants. Complex 1 exhibits spin-frustration behavior, and was fitted with a two-J model in the temperature range of 2300 K, which gives J1 = 0.92 and J2 = 2.23 cm1. Complexes 2 and 3 were fitted with the same model in the temperature range of 30300 K and 40300 K to give the exchange coupling constants J1 = 2.49, J2 = 4.84 cm1 and J1 = 4.18, J2 = 5.44 cm1, respectively.