Binuclear cobalt(II/II) and cobalt(II/III) chelates with O2N2 ligands: synthesis, structure and magnetic studies

Study on the Magneto-Structural Correlation of a New Dinuclear Cobalt(II) Complex with Double μ-Phenoxo Bridges

A new μ-phenoxo-bridged dinuclear cobalt(II) complex, [Co₂(L)₂(acac)₂(H₂O)] (1), has been synthesized by employing a new ligand, (4-methyl-2-formyl-6-(((2-trifluoromethyl)phenyl)methyliminomethyl) phenol) (HL). Structural analysis of complex 1 reveals that the geometry around cobalt centers is best described as a distorted octahedron and the distance of cobalt neighbors is 3.128(0) Å. The magnetic property studies indicate that complex 1 exhibits strong spin-orbit coupling effects and weak ferromagnetic coupling between two high-spin Co(II) centers linked by double μ-O_phenoxo bridges, with J = 1.87(2) cm^-1. The studies show that not only the Co-O-Co angle affects the alignment of the cobalt spins but also the dihedral angle between the CoOCo plane and the phenyl plane plays an important role in the magnetic coupling in this [Co₂O₂] system. Thus, the small bridging angles (96.96(11) and 96.91(11)°) and the large dihedral angles between the CoOCo plane and the phenyl plane (63.0(1) and 30.6(1)°) induce intramolecular ferromagnetic exchange interaction in complex 1.