Inducing Single-Molecule Magnetism in a Family of Loop-of-Loops Aggregates: Heterometallic Mn₄₀Na₄ Clusters and the Homometallic Mn₄₄ Analogue

Abstract

The syntheses, crystal structures, and magnetic properties of a new family of heterometallic Mn(40)Na(4) and homometallic Mn(44) loop-of-loops aggregates are reported. The reactions of [Mn(3)O(O(2)CMe)(6)(py)(3)]·py with 1,3-propanediol (pdH(2)) and 2-methyl-1,3-propanediol (mpdH(2)) in the presence of NaN(3) afforded [Mn(10)Na(μ(3)-O)(2)(O(2)CMe)(13)(pd)(6)(py)(2)](4) (1)(4) and [Mn(10)Na(μ(3)-O)(2)(O(2)CMe)(13)(mpd)(6)(py)(H(2)O)](4) (2)(4), respectively. Mn(40)Na(4) complexes (1)(4) and (2)(4) consist of four Mn(10) loops linked through Na(+) ions to give a supramolecular aggregate with a saddle-like topology. Magnetic characterization of compound (1)(4) showed that each Mn(10) loop has an S = 4 ground-state spin and displays frequency-dependent in-phase and out-of-phase ac susceptibility signals. It also exhibits hysteresis loops that, however, are not typical of single-molecule magnets (SMMs) due to the existence of interloop interactions between the neighboring Mn(10) units of (1)(4) through the diamagnetic Na(+) ions, and also intermolecular interactions between different Mn(40)Na(4) aggregates. The magnetically discrete Mn(44) analogue was targeted with high priority and finally prepared from the reaction of [Mn(3)O(O(2)CMe)(6)(py)(3)]·py with pdH(2) in the presence of Mn(ClO(4))(2)·6H(2)O. The loop-of-loops structure of [Mn(44)(μ(3)-O)(8)(O(2)CMe)(52)(pd)(24)(py)(8)](ClO(4))(OH)(3) (3) is essentially identical to those of (1)(4) and (2)(4), with the most significant difference being that the four Na(+) ions of (1)(4) and (2)(4) have been replaced with Mn(2+) ions. Compound 3 is thus best described magnetically as a Mn(44) cluster. In accord with this description and the stronger exchange coupling between the four Mn(10) loops expected through the connecting Mn(2+) ions, magnetic susceptibility measurements revealed that 3 has an S = 6 ground-state spin and displays frequency-dependent in-phase and out-of-phase ac signals. Magnetization vs dc field sweeps on single-crystals of 3 displayed scan rate- and temperature-dependent hysteresis loops confirming that complex 3 is a new SMM, and is thus the second largest Mn cluster and SMM reported to date.

A new dodecanuclear manganese single-molecule magnet from the arrangement of manganese triangles

“…4S). The small value of τ 0 , smaller than is typical for purely SMM behavior, is attributed to the low-lying excited states and weak intermolecular interactions; large clusters often give smaller τ 0 values [32][33][34][35][36][37][38]. The AC measurements suggest that complex 1·5MeOH·2H 2 O functions as a SMM, which is confirmed by hysteresis loops obtained from magnetization vs. DC field scans.…”

Nonemployed Simple Carboxylate Ions in Well-Investigated Areas of Heterometallic Carboxylate Cluster Chemistry: A New Family of {CuII4LnIII8} Complexes Bearing tert-Butylacetate Bridging Ligands

“…6 Although simple and flexible carboxylates (i.e., MeCO 2 yet attracted similar attention. Reasons that differentiate the Bu t CH 2 CO 2 − group from the structurally analogous pivalate ion (Bu t CO 2 − ) are mainly steric and partially electronic.…”

Synthesis, structure, and magnetic properties of a tetradecanuclear manganese complex

“…The synthesis and characterization of 3d transition metal complexes with various nuclearities and structure topologies are of interest because of their fascinating physical properties and interesting structures [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The uses of suitable types of ligands and appropriate reaction conditions have allowed the formation of a variety of high nuclear complexes.…”

“…The uses of suitable types of ligands and appropriate reaction conditions have allowed the formation of a variety of high nuclear complexes. There are many examples of high nuclearities in the field of manganese chemistry [6][7][8][9][10][11][12][13][14][15][16][17]. The synthesis of such complexes involves the use of multinuclear clusters as starting materials.…”

“…Some of the most successful starting materials employed for these reactions arise from the [Mn 3 O(O 2-CR) 6 (L) 3 ] n+ (n = 0, 1; R = various; L = terminal ligands) family, which have afforded a variety of new high nuclear complexes, such as Mn 9 [19], Mn 21 [11], and Mn 22 [13], and all of these manganese clusters show single-molecule magnet (SMM) behaviors. For example Mn 21 [10], Mn 22 [12], Mn 30 [15], and Mn 84 [17], which have pleasing structures, are synthesized from reactions using the mixed-valence SMM archetype [Mn 12 O 12 (O 2 CR) 16 (H 2 O) 4 ] (R = various) family as the starting materials. The mixed-valence [Mn 6 O 2 (Piv) 10 (4-Me-py) 2.5 (PivH) 1.5 ] [20] (PivH = t BuCO 2 H, 4-Mepy = 4-methylpyridine) can be used as the starting material, and has been shown to be a good candidate for the synthesis of MnLn complexes [20,21].…”