Modulation of architectures and magnetic dynamics in pseudotetrahedral cobalt(ii) complexes

Abstract

Two β-Diketiminate cobalt(II) compounds of formula [LCo(μ-Cl)]₂·2C₆H₁₄ (1) and [LCoClPy]·0.5C₇H₈·0.5C₆H₁₄ (2) (L = [PhC-(PhCN-Dip)₂]⁻, Dip = 2,6-ⁱPr₂C₆H₃) have been synthesized and structurally characterized by single crystal X-ray diffraction. Compound 1 exhibits a dinuclear structure, whereas 2 is a mononuclear structure having a pyridine ligand. The tetra-coordinate Co^II centers in both compounds show distorted tetrahedral geometry configuration. Magnetic measurements reveal that only 2 exhibits field-induced slow relaxation of magnetization with an effective spin-reversal energy barrier of 16.27 K, though large easy-axis magnetic anisotropies for both compounds are unveiled by the analysis of ab initio calculations. Dimeric Co–Co units in 1 indicate intramolecular antiferromagnetic interaction. Compared to individual Co^II fragment of 1, the first excited quartet state of 2 is strongly destabilized, leading to a smaller unquenched orbital angular momentum and D value. The comprehensive factors above are responsible for the difference in the magnetic behavior between 1 and 2.