Tuning of High Spin Ground State and Slow Magnetic Relaxation within Trimetallic Cyanide-Bridged {Ni II x Co II 9-x [W V (CN) 8 ] 6 } and {Mn II x Co II 9-x [W V (CN) 8 ] 6 } Clusters.

Two series of trimetallic {Ni ^II _x Co ^II _9-x [W ^V (CN) ₈ ] ₆ } (NiCoW) and {Mn ^II _x Co ^II _9-x [W ^V (CN) ₈ ] ₆ } (MnCoW) (x=1-8) crystalline solid-solutions were constructed and systematically studied by SEM EDX, single-crystal X-ray diffraction (SC XRD), and magnetic measurements. The atomic Ni:Co:W and Mn:Co:W ratios in the solid state follow the stoichiometric concentration in the mother MeOH solutions fairly well. The structural studies revealed a definite strong tendency of smaller 3d ions to locate in the central [M(μ-NC) ₆ ] moiety of the skeleton: Ni ^II over the Co ^II and Co ^II over Mn ^II . In contrast, the external fac-[M(μ-NC) ₃ (MeOH) ₃ ] are consecutively occupied by the mixture of 3d metal ions, accessible according to the stoichiometry of the mother solutions. The DC magnetic χT(T) and M(H) curves illustrate the continuous tendency of change with x along both series, nicely reproducing the changes of the theoretical high spin in the ground state S _gr , assuming the ferromagnetic ^HS Co ^II -NC-W ^V and antiferromagnetic Mn ^II -NC-W ^V interactions established by numerous literature reports. The AC magnetic measurements indicate the occurrence of slow magnetic relaxation, with the highest energy barrier ΔE/k _B of 26 K for the Ni ₆ Co ₃ W ₆ congener and of 17 K for the Mn ₆ Co ₃ W ₆ congener, and relatively large values of distribution parameter α. The values of ΔE are correlated with possible anisotropy of distribution of fac-[Co ^II (μ-NC) ₃ (MeOH) ₃ ] moieties at the external corners of the cube substructure.
(© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)