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

Two β-Diketiminate cobalt(II) compounds of formula [LCo(μ-Cl)] 2 ·2C 6 H 14 (1) and [LCoClPy]·0.5C 7 H 8 ·0.5C 6 H 14 (2) (L = [PhC-(PhCN-Dip) 2 ] - , Dip = 2,6- i Pr 2 C 6 H 3 ) 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.