Tuning of High Spin Ground State and Slow Magnetic Relaxation within Trimetallic Cyanide‐Bridged {Ni^II_xCo^II_9−x[W^V(CN)₈]₆} and {Mn^II_xCo^II_9−x[W^V(CN)₈]₆} Clusters

Abstract

Two series of trimetallic {Ni Co [W (CN) ] } (NiCoW) and {Mn Co [W (CN) ] } (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) ] moiety of the skeleton: Ni over the Co and Co over Mn . In contrast, the external fac-[M(μ-NC) (MeOH) ] 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 , assuming the ferromagnetic Co -NC-W and antiferromagnetic Mn -NC-W interactions established by numerous literature reports. The AC magnetic measurements indicate the occurrence of slow magnetic relaxation, with the highest energy barrier ΔE/k of 26 K for the Ni Co W congener and of 17 K for the Mn Co W congener, and relatively large values of distribution parameter α. The values of ΔE are correlated with possible anisotropy of distribution of fac-[Co (μ-NC) (MeOH) ] moieties at the external corners of the cube substructure.

Trinuclear Cyanido‐Bridged [Cr2Fe] Complexes: To Be or not to Be a Single‐Molecule Magnet, a Matter of Straightness

“…[15][16][17][18][19][20][21][22][23][24][25][26] Such complexes can also be used as metalloligands by including in their apical positions groups such as cyanides, [27] which are certainly the most important bridging ligands in molecularbased magnetic systems, including molecular nanomagnets. [28][29][30][31][32] Following this approach, SCMs with nearly collinear local anisotropy directions have been obtained from heptacoordinated [CrL N3O2R (CN) 2 ] À (R = Ph, NH 2 , Scheme 1) and PBP Fe II or Ni II derivatives. [33,34] These cyanido-bridged systems are characterized by ferromagnetic interactions for CrFe and CrNi systems while they are antiferromagnetic in CrMn species.…”

Site Selectivity for the Spin States and Spin Crossover in Undecanuclear Heterometallic Cyanido-Bridged Clusters

“…1.4 × 2.5 × 2.5 nm ( 4 R / 4 S ), considering the distance between the most remote atoms along three cluster axes. Various metallic core compositions embedded within the same topological scaffold and the related SCO scenarios open a promising route for molecular design toward advanced cocrystal salts involving switchable polynuclear clusters , and molecular hierarchical systems such as heterotrimetallic solid solutions ,,, or core–shell composites; the solubility and stability of these forms in various organic solvents might be one of the prerequisites in further research. Moreover, the research on SCO transitions in multisite clusters might provide better characteristics (e.g., larger cooperativity, SCO site speciation, multistep transitions, etc.…”

“… 50 Particular attention was paid to the family of 15-nuclear {M 9 M′ 6 } (M = Mn II , Fe II , Co II , Ni II ) clusters easily affordable by crystallization from the methanol (MeOH) solution of the 3d metal salts and [M(CN) 8 ]. 3 − 60 The composition of the core of these clusters might be appropriately adjusted to achieve HS in the ground state, 52 slow magnetic relaxation, 53 , 54 or phase transitions accompanied by CT 55 − 57 and SCO. 58 , 59 The SCO phenomena were systematically observed for the central [Fe(μ-NC) 6 ] site owing to the favorable ligand-field stabilization energy, whereas the external [Fe(μ-NC) 3 (MeOH) 3 ] sites remained in the HS state during the transition.…”

“…As an essential contribution to the above studies, we and others applied [M­(CN) 8 ] 3–/4– (M = W, Mo, Nb, Re) building blocks of diverse structural and redox nonrigidity , to promote thermal-induced and photoinduced charge transfer (CT) within W V/IV –Co II/III , W V/IV –Fe II/III , or Mo IV –Cu II pairs and the SCO effect in M V/IV –Fe II (M = W, Mo, Nb, Re) coordination networks. − Moreover, the SCO behavior and light-induced excited-spin-state trapping effects (LIESST) were also noted at the Fe II sites in discrete structures, such as a [Fe 2 M 2 ] molecular rhombus , and a [Fe 4 M 2 ] octahedron, − with the latter one featuring also site-selective double photoswitching of the Fe II and Mo IV sites . Particular attention was paid to the family of 15-nuclear {M 9 M′ 6 } (M = Mn II , Fe II , Co II , Ni II ) clusters easily affordable by crystallization from the methanol (MeOH) solution of the 3d metal salts and [M­(CN) 8 ]. − The composition of the core of these clusters might be appropriately adjusted to achieve HS in the ground state, slow magnetic relaxation, , or phase transitions accompanied by CT − …”