Two edge-sharing MnII4MnIII6 supertetrahedra give an anisotropic S = 28 ± 1 MnII6MnIII11 complex

Abstract

A complex with a [Mn(II)(6)Mn(III)(11)] core results via formal fusion of two isotropic Mn(II)(4)Mn(III)(6) supertetrahedra along a common edge leading to a high spin ground state anisotropic system showing Mvs. H hysteresis loops below 1 K.

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

“…Thefit to the thermally activated region above about 0.1 Kgave t 0 = 7 10 À14 sa nd U eff = 19 K. Thes mall value of t 0 ,s maller than is typical for purely SMM behavior,i sa ttributed to the lowlying excited states and the weak intermolecular interactions and is acommon situation for large clusters. [2,22,23,29] At about 0.1 Ka nd below,t he relaxation becomes temperature-independent as expected for relaxation by ground-state QTM, that is,via the M S =AE 61/2 levels of the S = 61/2 spin manifold.…”

“…One ideal structural type to act as abuilding block in high nuclearity clusters is the [Mn III 6 Mn II 4 (m 4 -O) 4 ] 18+ supertetrahedral core which combines ab eautiful, high symmetry (T d ) metal topology and interesting magnetic properties. [19] In addition, it has been stabilized in discrete form with several ligands [19][20][21] and under various reaction conditions,a nd has appeared as the repeating unit in zero-dimensional Mn 17 [22,23] and Mn 19 [24] clusters and in the giant Mn 36 Ni 4 "loop-of-loops and supertetrahedra" aggregate, [12] , with that of 1 describing an "A rchimedean solid" called ac uboctahedron. Additionally,t he compounds are structurally related, with the core of 2 being almost identical to afragment of that of 1.Magnetism studies revealed the existence of dominant ferromagnetic exchange interactions in both 1 and 2 leading to ground-state spin values of 61/2 and 51/2, respectively.I na ddition, the magnetocaloric effect for both complexes is seen to develop over as ignificantly wide temperature range.F inally,c ompound 1 displays single-molecule magnet (SMM) behavior and is the second largest homometallic 3d SMM reported to date.…”

“…Thea symmetric unit of 1 [25] consists of two independent quarters of the Mn 49 cation (Figure 1a 4 ] 18+ supertetrahedral core, [19][20][21][22][23][24] whereas the m 3 -MeO À ligands bridge three Mn 3+ ions.T he peripheral ligation is completed by 24 fully deprotonated hp 2À ligands connecting two Mn 2+ and one Mn 3+ ions in a h 2 :h 2 -m 3 mode,s ix severely disordered HCO 2 À ligands bridging exclusively Mn 3+ ions, and 12 terminal DMF molecules bound to the 12 outer Mn 2+ ions.…”

“…Interestingly,t he cores of 1 and 2 are also related to the [Mn III 11 Mn II 6 (m 4 -O) 8 ] 29+ core of af amily of Mn 17 clusters reported in 2009 (see Figure 3and Figure S4 in the Supporting Information). [22,23] These Mn 17 clusters consist of two edgesharing [Mn III 6 Mn II 4 (m 4 -O) 4 ] 18+ supertetrahedral units and display ferromagnetic exchange interactions.I nf act, one of these Mn 17 analogues combines an S = 37 spin ground state and SMM behavior and is the largest-spin SMM reported. [22] Complex 2 contains two [Mn III 11 Mn II 6 (m 4 -O) 8 ] 29+ fragments, nearly identical to the core of the above discussed Mn 17 cluster,s haring a m 5 plane,w hereas complex 1 consists of four such units sharing two m 5 planes with their neighboring units.B oth 1 and 2 are nanosized clusters and among the largest discrete (0D) 3d metal clusters with maximum dimensions of about 2.5 and 2.2 nm and molecular weights of approximately 8400 and 4800 gmol À1 ,r espectively,w ith compound 1 being smaller only than Mn 84 and Fe 64 clusters.…”

“…To further probe the ground-state spin of the two complexes,m agnetization (M)v ersus dc field measurements at applied magnetic fields (H)a nd temperatures in the 1-70.0 kG and 1.8-10.0 Kr anges,r espectively,w ere performed (see the Supporting Information for am ore detailed discussion). Thed ata are shown in Figures S9 and S10 for 1·10DMF and 2·DMF,respectively,asreduced magnetization [22,23] (top;see text for details), respectively,highlightingtheir structural relationship.The light blue planes through the cores of 1 and 2 are used to emphasize the common M 9 plane of the two M 29 subunits, related to the structure of 2,w ithin the M 49 cuboctahedral core of 1 (see the text for details). Color code:M n 3+ = blue, Mn 2+ = pink, Na + = purple, O = red.…”