Magnetic “Molecular Oligomers” Based on Decametallic Supertetrahedra: A Giant Mn₄₉ Cuboctahedron and its Mn₂₅Na₄ Fragment

Abstract

Two nanosized Mn49 and Mn25Na4 clusters based on analogues of the high-spin (S=22) [Mn(III)6Mn(II)4(μ4-O)4](18+) supertetrahedral core are reported. Mn49 and Mn25Na4 complexes consist of eight and four decametallic supertetrahedral subunits, respectively, display high virtual symmetry (O(h)), and are unique examples of clusters based on a large number of tightly linked high nuclearity magnetic units. The complexes also have large spin ground-state values (Mn49: S=61/2; Mn25Na4: S=51/2) with the Mn49 cluster displaying single-molecule magnet (SMM) behavior and being the second largest reported homometallic SMM.

Quantum Monte Carlo simulations of a giant {Ni21Gd20} cage with a S = 91 spin ground state

“…11) data give a maximum value of 34.8 J kg –1  K –1 at 3 K and 7 T for 1 (Supplementary Fig. 12), which is comparable to other Gd-based polymetallic clusters (Supplementary Table 3) 2 , but smaller than the maximum entropy value judged by the function of –∆ S m  = n R ln(2  S  + 1) = 64.7  R , which corresponds to 45.8 J kg –1  K –1 for 1 . The coupling between the Gd(III) and Ni(II) ions, as well as their finite magnetic anisotropies, reduce the maximum achievable entropy content because these interactions partly lift the level degeneracy at H  = 0.…”

“…Paramagnetic metal clusters possessing large ground spin state ( S ) often show attractive magnetic behavior with potential applications such as single-molecule magnets (SMMs) 1,2 , magnetic refrigerants 3,4 , and contrast agents for magnetic resonance imaging (MRI) 5,6 . To date, the highest ground spin states reported are S  =  83 / 2 for a {Mn 19 } cage 7 , S  =  61 / 2 for a {Mn 49 } cage 2 , S  = 45 for an {Fe 42 } cage 8 , and S  = 60 for a {Fe 10 Gd 10 } nano-torus 9 .…”

“…To date, the highest ground spin states reported are S  =  83 / 2 for a {Mn 19 } cage 7 , S  =  61 / 2 for a {Mn 49 } cage 2 , S  = 45 for an {Fe 42 } cage 8 , and S  = 60 for a {Fe 10 Gd 10 } nano-torus 9 . The accurate magnetic analysis of such giant species is challenging because the number of energy levels increases exponentially with the magnitude and number of spins.…”

Bis-tris propane as a flexible ligand for high-nuclearity complexes

“…We were able to employ a pre-formed Cu II Bis-tris propane complex, which contains multiple, latent hydroxyl binding sites, to target the trapping and encapsulation of an inner metal-oxo core. The choice of Cu II as the central ion increases the flexibility of the strategy further, due to its range of typical coordination environments from [4] to [4 + 2]. We were delighted that two of the first heterometallic complexes that we isolated using this strategy contained a 'core-shell' {Mn 18 and complex 9 has a more compact core with higher symmetry (S 6 ).…”

“…Current areas of interest relate to single-molecule magnets (SMMs) [4,5]; magnetic refrigerants [6]; qubits [7]; complexes with toroidal moments [8]; the magnetic behavior of high symmetry systems [9][10][11]; magnetic bistability on surfaces [12]; mimics of the oxygen evolution center in photosystem II [13], and water oxidation electrocatalysis [14]; MRI contrast agents [15] and as precursors for magnetic nanoparticles [16], or lithographic resists [17]. However, the synthetic challenges involved in isolating such systems [18] and the search for emergent properties in larger and larger systems is also a major driving force [19][20][21][22][23].…”