Variation in the electron count and ground state of [Mn₁₂O₁₂(O₂CR)₁₆(H₂O)₄](R = Me or Ph) by metal substitution and redox changes: preparation and properties of [Mn₈Fe₄O₁₂(O₂CMe)₁₆(H₂O)₄]·4H₂O·2MeCO₂H and [NPrⁿ₄][Mn₁₂O₁₂(O₂CPh)₁₆(H₂O)₄]·H₂O

Abstract

Variation in the ElectronCount and Ground State of [Mn120,2(02CR)16(H20)4] (R = M e or Ph) by Metal Substitution and Redox Changes: Preparation and Properties of [ M n8Fe40 2(02CMe) 6( H20)4]*4H20e2MeC02H and [ N Prn4] [ M n 20 2( 02CP h) 6( H20)4]*H20

Magnetic Signatures of Hydroxyl‐ and Water‐Terminated Neutral and Tetra‐Anionic Mn12‐Acetate

“…The results observed here are generic and it is reasonable to expect similar effects in any stable molecular system that has four spin‐carrying transition metal ions that are coordinated by water molecules. The inclusion of FLOSIC provides a description of HOMO‐level eigenvalues, in accord with computed energetics, and reinforces experimental work suggesting the tetra‐anion is likely to decompose but with a modest degree of exothermicity. Proper estimates of the HOMO/fm levels is key to determining whether soft decomposition of a highly charged tetra‐anion is a viable route to decomposition of multiple water molecules into hydroxyl‐hydrogen pairs.…”

“…Examples where changes in resonant tunneling of magnetization and magnetic spectra have been shown to be dependent on changes in metal‐center charge states, rearrangement of hydrogen atoms, or pressure or sorbent induced structural changes are well documented in magnetic molecules and materials composed of magnetic molecules. A dramatic example, theoretically predicted by Garg and observed in the Fe 8 ‐molecular magnet by Wernsdorfer and Sessoli et al is that a small breaking in uniaxial symmetry in a molecular magnet leads to a very sensitive topologically quenched tunnel splitting that is associated with a tri‐axial single‐spin Hamiltonian, for example, .…”

“…Here, we investigate the use of magnetic spectra for situations involving bond breaking. Through computation, we show that magnetic signatures of a specific molecule, which is known to be stable in the neutral, anionic, di‐anionic, and tri‐anionic charge states, but is believed to decompose in the tetra‐anionic state, provide a unique means for determining whether a hydrogen‐production reaction is more likely to proceed in the neutral state or, due to a potential decomposition mechanism, to be accelerated by the addition of a fourth electron. In view of the fact that thermionic emission in multiply charged negative anions is known to be delayed by detachment barriers, we suggest that similar quantum mechanics could allow for structural, rather than electronic, decomposition of the tetra‐anionic molecule selected for consideration here.…”

Large Clusters of Metal Ions: The Transition from Molecular to Bulk Magnets

“…9). T h e carboxvlates that have been investigated (38)(39)(40)(41) (42). T h e magnetic properties of these materials are, however, less interesting than those of the parent Mn,, cluster.…”

MeOH-coordinated Mn12 single-molecule magnet: structure and magnetic properties of [Mn12O12(OAc)16(MeOH)4]

“…Complex 1 also shows the properties of macroscopic quantum tunneling of magnetization with a large ground state spin S (=10), and a negative D (= À0.72 K) [1]. For grasping its chemical characters and properties more thoroughly, many Mn 12 clusters have been prepared by the chemical modification including substitutions of bridging acetates to other carboxylates [4][5][6] or to oxo anions other than carboxylates [7][8][9], and partial substitutions of a peripheral Mn III ion to an Fe III ion [10] or a Cr III ion [11]. Although most of Mn 12 complexes reported so far have four coordinating water molecules, only a few examples [4,[12][13][14][15] are known to have three or two coordinating water molecules, and only one complex does not contain any coordinating water molecules [16].…”