Establishment of magneto-structural model remains a critical challenge in estimating various spin Hamiltonian parameters and magnetic exchange mechanisms in molecular magnets. Here we successfully synthesized two isostructural coordination polymers (CPs), namely, Co3 (L) 2 (4, 4′-bpy) 2 (H2O) 2· (H2O) 4n (1) and Ni3 (L) 2 (4, 4′-bpy) 2 (H2O) 2n (2), by using 3- (2, 4-dicarboxyphenyl) -4-carboxylpyridine (H3L) under solvothermal conditions. Meanwhile, the reasonable magneto-structural model has been determined via density functional theory (DFT) calculations, complex 1 exhibits antiferromagnetic (AFM) interactions based on the contribution of mononuclear Co (II), while complex 2 shows ferromagnetic (FM) coupling mainly from binuclear Ni (II). Moreover, ab initio CASSCF/RASSI-SO with the OpenMolcas unambiguously reveals large positive zero-field split (ZFS) parameters D value (87. 4 cm–1) and gx, y > gz, which exhibit easy-plane anisotropy for 1. Conversely, complex 2 is characterized as isolated easy-axis anisotropy, evidenced by their negative D value (−25. 5 cm–1) and gz > gx, y, showing ferromagnetic (FM) coupling. Overall, this work offers a kind of thinking of designing isostructural CPs with different magnetic properties.
Chen et al. (Mon,) studied this question.