Binuclear cobalt() and two-dimensional manganese() coordination compounds self-assembled by mixed bipyridine-tetracarboxylic ligands with single-ion magnet properties

A cobalt( ii ) complex and manganese( ii ) coordination polymer, formulated as [Co 2 (H 2 btca)(mbpy) 4 ][H 2 btca]·4H 2 O ( 1 ) and {Mn 2 (btca)(mbpy) 2 (H 2 O) 2 } n ( 2 ) (H 4 btca = 1,2,4,5-benzenetetracarboxylic acid; mbpy = 4,4′-dimethyl-2,2′-bipyridyl), constructed by mixed bipyridine-tetracarboxylic ligands were synthesized and characterized. Single-crystal structural analyses reveal that compound 1 is a discrete neutral binuclear molecule, while compound 2 is a two-dimensional (2D) coordination polymer. The metal ions in these compounds are well isolated, with an intramolecular Co 2+ Co 2+ distance of 9.170 Å for 1 and Mn 2+ Mn 2+ separation of 10.984 and 11.164 Å for 2 due to the bulk tetracarboxylic linker. This isolation gives rise to a single-ion magnetism origin of the compounds. Magnetic studies reveal a large zero-field splitting parameter D of 82.6 cm −1 for 1 , while a very small D of 0.42 cm −1 was observed for 2 . Interestingly, dynamic ac magnetic measurements exhibited slow magnetic relaxation under the external dc field of the two compounds, revealing the field-supported single-ion magnet (SIM) of 1 and 2 . The detailed theoretical calculations were further applied to understand the electronic structures, magnetic anisotropy, and relaxation dynamics in 1 and 2 . Combined with our recently reported compound ( Eur. J. Inorg. Chem ., 2022, e202200354), the foregoing results provide not only a rare binuclear cobalt( ii ) SIM and the first 2D manganese( ii ) SIM coordination polymer but also a bipyridine-tetracarboxylic ligand approach toward novel SIMs. A rare binuclear cobalt( ii ) and the first 2D manganese( ii ) coordination compounds constructed by mixed bipyridine-tetracarboxylate were reported to exhibit field-supported slow magnetic relaxation behavior.