Structure and magnetism of decanuclear and octadecanuclear manganese(II/III) triethanolamine clusters

Abstract

Two new potential single molecule magnets [Mn(10)O(3)(O(2)CCH(3))(6)(tea)(teaH)(3)(teaH(2))(3)][NO(3)](2).3H(2)O (1) and [Mn(18)(N(3))(12)O(12)(tea)(2)(teaH)(4)(OMe)(MeOH)].2MeOH.H(2)O.Et(2)O (2) have been synthesised using manganese(II) nitrate, the tripodal ligand triethanolamine (teaH(3)) and co-ligands such as acetate for 1 and azide for 2. Both compounds are mixed-valent with 1 consisting of 4 Mn(II) and 6 Mn(III) ions and 2 consisting of 3 Mn(II) and 15 Mn(III) ions. Complex 1 has a near planar Mn(7)(II/III) disc-like core with 3 Mn(II) ions positioned on the periphery of the disc, forming a star-like geometry. Complex 2 contains a hexa-capped truncated tetrahedral core. Variable temperature DC magnetic susceptibility data collected in 2, 1, 0.1 and 0.01 T fields, and in the 2-300 K temperature range, for 1 and 2, indicate a large ground spin-state for both compounds. Using a new approach to calculating the DC Mvs. H isotherms (or isofield Mvs. H/T curves) by means of the thermal population of Zeeman levels generated from a group of closely spaced S states (within 9 cm(-1) of ground), the ground S of 1 is 10. The ZFS term, D, is close to zero. For 2 , the magnetisation isotherms, and low temperature susceptibilities, point to a ground state spin of (21)/(2) with many closely spaced spin states (probably from (17)/(2) to (35)/(2)) close in energy, the lowest Zeeman level energies of which change as the field increases. AC magnetic susceptibility data show frequency-dependent out-of-phase signals indicating both clusters are possibly single molecule magnets. Extrapolation of the in-phase component, chi'(M)T, to 0 K suggests spin ground state of S = 10 for 1 and (21)/(2) for 2 , in agreement with the DC data.

Evidence of Spin Canting, Metamagnetism, Negative Coercivity and Slow Relaxation in a Two‐Dimensional Network of {Mn6} Cages

“…The plots of M vs. H/T at different temperatures do not superpose on a single master curve, suggesting the presence of a significant anisotropy in 1 and/or the population of low‐lying excited states, which is expected to occur in Mn II /Mn III complexes . Indeed, the M–H isotherms at 1.8 and 2 K display an inflection point at about 20 kG and at a little above 10 Nµ B , indicating a spin change within the {Mn 6 } subunits.…”

Bis{μ2-2-[(2-hydroxyethyl)(methyl)amino]ethanolato}bis(μ3-N-methyl-2,2′-azanediyldiethanolato)tetrakis(thiocyanatato-κN)dichromium(III)dimanganese(II) dimethylformamide tetrasolvate

“…For background to polynuclear chromium-containing complexes, see: McInnes et al (2005); Affronte et al (2005). For the use of amino alcohols with versatile bridging modes in generating such metal clusters, see: Langley et al (2009); Ferguson et al (2008); Saalfrank et al (2001). For background to direct synthesis, see: Kokozay & Shevchenko (2005).…”

“…Winpenny and coworkers devoted to magnetic studies of high-nuclear cages and wheels (McInnes et al, 2005;Affronte et al, 2005). At the same time, the potential of alcohols and amino alcohols in generating such metal clusters was widely explored (Saalfrank et al, 2001;Langley et al, 2009;Ferguson et al, 2008).The polydentate alkoxo ligands possessing versatile bridging modes were recognized as promising reagents for synthesis of new heterometallic complexes. Previously we have demonstrated that amino alcohols represent a powerful tool for assembling polynuclear metal complexes in conditions of the synthetic approach named "direct synthesis of coordination compounds".…”

Synthesis, Structure, and Magnetic Properties of a Mn4 Cluster derived from Benzimidazole‐Alcohol Ligands

“…In the development of new synthesis routes, the selection of the organic ligands is extremely significant. Many ligands have been explored for the formation of 3d metal clusters with various topologies and magnetic properties, such as alcohol amines,17 pyridyl alcohols,18 pyridyl ketone oximes,19 salicylaldoximes,20 alkyl alcohols,21 aromatic alcohols,22 and so on 23,24…”