Synthesis and Characterization of a Mn₂₂ Single-Molecule Magnet and a [Mn₂₂]_n Single-Chain Magnet

Abstract

The reactions of [Mn12O12(O2CEt)16(H2O)4] with phenylphosphinic acid (PhHPO2H) in MeCN and MeCN/CH2Cl2 have led to isolation of [Mn22O12(O2CEt)22(O3PPh)8(H2O)8] (2) and [Mn22O12(O2CEt)20(O3PPh)8(O2PPhH)2(H2O)8]n (3), respectively, both containing PhPO3(2-) groups from in situ oxidation of PhHPO(2)(-). Complex 2 is molecular and consists of two Mn9 subunits linked by four additional Mn atoms. Complex 3 contains almost identical Mn22 units as 2, but they are linked into a one-dimensional chain structure. The Mn22 unit in both compounds is mixed-valence Mn(III)18, Mn(II)4. Solid-state, variable-temperature dc magnetic susceptibility and magnetization measurements were performed on vacuum-dried samples of 2 and 3, indicating dominant antiferromagnetic interactions. A good fit of low-temperature magnetization data for 2 could not be obtained because of problems associated with low-lying excited states, as expected for a high nuclearity complex containing Mn(II) atoms. An approximate fit using only data collected in small applied fields indicated an S = 7 or 8 ground state for 2. Solid-state ac susceptibility data established that the true ground state of 2 is S = 7 and that the connected Mn22 units of 3 are ferromagnetically coupled. Both 2 and 3 displayed weak out-of-phase ac signals indicative of slow magnetization relaxation. Single-crystal magnetization versus applied dc field scans exhibited hysteresis loops for both compounds, establishing them as new single-molecule and single-chain magnets, respectively. Complex 2 also showed steps in its hysteresis loops characteristic of quantum tunneling of magnetization, the highest nuclearity molecule to show such QTM steps. Arrhenius plots constructed from dc magnetization versus time decay plots gave effective barriers to magnetization relaxation (U(eff)) of 6 and 11 cm(-1) for 2 and 3, respectively.

Correlating the magic numbers of inorganic nanomolecular assemblies with a {Pd 84 } molecular-ring Rosetta Stone

“…In this way it appears possible to predict the assembly of nanoscale architectures, based on an established minimal building block set, symmetry number, and suggesting some cluster nuclearity magic numbers. As such, we predict the fivefold system fPd 12 g 5 ≡ fPd 60 g that we postulate could have a "fullerene-like" ball structure (19). This proposal is also consistent with the classic example of fMo 132 g ≡ fMo 22 g 6 -ball (7), which has a shape of sphere, rather than ring.…”

“…By using the same arguments we predict that the assembly and isolation of the fPd 60 g (12 × 5), fPd 72 g (12 × 6), and fPd 96 g (12 × 8) but also it is worth noting that the fPd 60 g could also be accessed by other symmetries making the structure of this appealing magic number even more likely. It is interesting to note, in terms of predictions, the existence of the fMn 70 g has been experimentally revealed, although the structure has not been formally published (19). Although we present a single new fPd 84 g structure here, this theoretical framework connects three previously unconnected cluster families (with nuclearities >60) with eight cluster types: fMn 70 g, fMn 84 g, fPd 84 g, fMo 102 g, fMo 132 g, fMo 154 g, fMo 176 g, and fMo 368 g, providing validation of this framework.…”

A toolbox of building blocks, linkers and crystallisation methods used to generate single-chain magnets

“…26), for example 6-chloro-2-pyridinol reported by the group of Winpenny (Figs. 26 and 27) [33], as well as phenylphosphinate reported in the synthesis of a few different SCMs [100,104,106], and diphosphonate used by Palii, Tsukerblat, Dunbar and co-workers (Fig. 26) [26].…”

Diverse Structures and Magnetism of Cobalt(II) and Manganese(II) Compounds with Mixed Azido and Carboxylato Bridges Induced by Methylpyridinium Carboxylates

“…[3][4][5][6][7][8] These characteristics have allowed for the single bridges (EE = end-to-end); 6 is a layer compound in which chains similar to those in 5 are cross-linked by a m 3 -1,1,3-N 3 azido group. Magnetically, the three Co II compounds (1, 3, and 5) all exhibit intrachain ferromagnetic interactions but show distinct bulk properties: 1 displays relaxation dynamics at very low temperature, 3 is an antiferromagnet with field-induced metamagnetism due to weak antiferromagnetic interchain interactions, and 5 behaves as a noninnocent single-chain magnet influenced by weak antiferromagnetic interchain interactions.…”