In order to probe the magnetic relaxation mechanism of 3d-4f complexes systematically, two “Butterfly” MII 2DyIII 2 complexes related to our previously reported butterfly compound, [Zn2Dy2(L)4(Ac)2(DMF)2]·4CH3CN (1), and formulated as [Co2Dy2(L)4(Ac)2(DMF)2]·3CH3CN (2) and [Ni2Dy2(L)4(Ac)2(DMF)2]·3CH3CN (3) are prepared and characterized. In comparison to complex 1, the replacement of CoII or NiII with ZnII led to the effective quenching of quantum tunneling of the magnetization (QTM) in complexes 2 and 3. Obviously, the introduction of 3d-4f spin–spin exchange can be important in determining the overall magnetic behaviors of 3d-4f {MII 2DyIII 2} “Butterfly” systems.