A Ferromagnetically Coupled Mn₁₉ Aggregate with a Record S=83/2 Ground Spin State

Abstract

Dedicated to Professor Hansgeorg Schnöckel on the occasion of his 65th birthday.The first evidence of single molecule magnet (SMM) behavior was discovered in the mixed-valence compounds [Mn [1] In the quest to synthesize SMMs that show hysteresis at higher temperatures, it has been recognized that large ground-state spins and a uniaxial anisotropy (large negative D and small E considering the following Hamiltonian anisotropy term:It is thus of interest to discover how to obtain the largest-spin ground state possible for a given size of aggregate. As well as having four unpaired electrons in its high-spin state, the Mn III ion is particularly useful for introducing large anisotropies through the presence of Jahn-Teller distortions in this configuration and has been the most thoroughly studied candidate for synthesizing new SMMs. Amongst the large number of aggregates containing manganese(III) in the literature, a Mn 25 cluster has been reported as having a ground spin state of 51/2.[4] Herein we report on the realization of the maximum-spin ground state of 83/2 for the aggregate [Mn

Detailed Ab Initio First-Principles Study of the Magnetic Anisotropy in a Family of Trigonal Pyramidal Iron(II) Pyrrolide Complexes

“…11À13 Note that the proportionality of D to 1/S 2 is not specific to the case of magnetically interacting ions in clusters but is a fundamental result of rigorous theory as described in detail in ref 10. It has already been verified experimentally that clusters exhibiting large values of S tend to show small values of D. 9 For instance, in the highest spin ground state yet observed for a molecule, S = 83/2, 14 D is so small that no slow magnetic relaxation could be detected, despite the comparatively large local anisotropy due to the Mn(III) ions involved in the cluster.…”

On the Possibility of Magneto-Structural Correlations: Detailed Studies of Dinickel Carboxylate Complexes

“…14 This has encouraged a shift towards the use of ions with a large intrinsic anisotropy, since these are more likely to translate to a large D in clusters (the cluster D approximates to a tensor sum of the single ion anisotropy terms). Lanthanides have proven to be very promising in this regard, with many of the recent energy barrier record holders utilizing their high intrinsic spin and anisotropy terms.…”

Structure of cis-dichlorobis(1,10-phenanthroline)manganese(II) and cis-dichlorobis(2,2´-bipyridine)manganese(II)

“…Manganese complexes are of current interest in studies of molecular magnetism and in applications as magnetic recording (Ako et al, 2006;Aromi & Brechin, 2006) and manganese-enhanced MRI (Koretsky& Silva, 2004), and they can serve as model compounds of the bioinorganic chemistry of manganese (Deeth, 2008;Dismukes, 2006) including O 2 -evolving center of photosystem II (Umena et al, 2011) and various manganese-containing redox enzymes as dioxygenases (Georgiev et al, 2006), oxalate oxidase (Opaleye et al, 2006), catalase (Whittaker, 2012), superoxid dismutase (Friedel et al, 2004) and peroxidase (Sundaramoorthy et al, 2010). More manganese complexes especially for catalase and/or superoxide dismutase mimetics contain chelating N,N-donor ligands as 1,10-phenanthroline or 2,2´-bipyridine (Devereux et al, 1996;Geraghty et al, 1998;Kani et al, 2008;McCann et al, 1998;Viossat et al, 2003).…”