Ln-based single-molecule magnets (SMMs) are a crucial subject for molecular spintronics, in which the molecular spin is utilized for information processing. Previous studies have shown that Dy complexes have strong magnetic anisotropies and large activation barriers (E) of spin flipping among spin up and spin down states. As a result, Dy complexes have been developed as high-performance molecular magnets. Recently, organometallic Dy complexes that have a strong magnetic anisotropy or high symmetry around the Dy ion with a large E have been reported. In this system, a (weak) CF is a dominant source of the perturbation to resolve the degeneration of ground multiplet ( 6 H15/2) so that the axial magnetic states are stabilized. Therefore, an electrostatic CF has been used to control the physical properties of the f-electrons.