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

Three new isostructural coordination polymers, namely, [M 4 (μ 3 ‐OMe) 4 (nic) 4 ] n [M = Mn II ( 1 ), Fe II ( 2 ), and Co II ( 3 ); Hnic = nicotinic acid], have been solvothermally synthesized and magnetically characterized. Single‐crystal X‐ray diffraction study reveals that compounds 1 – 3 are three‐dimensional frameworks, which are constructed through {M 4 (μ 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 2–300 K, which gives J 1 = –0.92 and J 2 = –2.23 cm –1 . Complexes 2 and 3 were fitted with the same model in the temperature range of 30–300 K and 40–300 K to give the exchange coupling constants J 1 = –2.49, J 2 = 4.84 cm –1 and J 1 = –4.18, J 2 = 5.44 cm –1 , respectively.