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Article Dans Une Revue Inorganic Chemistry Année : 2009

Spin Maximization from S=11 to S=16 in Mn-7 Disk-Like Clusters: Spin Frustration Effects and Their Computational Rationalization

Theocharis C. Stamatalos
  • Fonction : Auteur
D. Foguet-Albiol
  • Fonction : Auteur
Katye M. Poole
  • Fonction : Auteur
Khalil A. Abboud
  • Fonction : Auteur
Ted A. O'Brien
  • Fonction : Auteur

Résumé

The use has been explored in Mn cluster chemistry of N-3(-) or Cl- in combination with N-methyldiethanolamine (mdaH(2)) or triethanolamine (teaH(3)). The reactions of Mn(ClO4)2 center dot 6H(2)O, NEt3, NaN3, and either mdaH(2) or teaH(3) (1:2:1:2) in DMF/MeOH afford {[Na(MeOH)(3)][MN7(N-3)(6)(mda)(6)]}(n) (1) and {Na[Mn-7(N-3)(6)(teaH)(6)]}(n) (2), respectively, whereas the 2:1:1 reaction of MnCl2 center dot 4H(2)O, mdaH(2), and NEt3 in MeCN gives (NHEt3)[Mn7Cl6(mda)(6)] (3). Similar reactions using (NBu4N3)-N-n in place of NaN3 gave (NHEt3)[Mn-7(N-3)(6)(mda)(6)] (4) and (NHEt3)[Mn-7(N-3)(6)(teaH)(6)] (5). The Mn-7 anions consist of a Mn-6 hexagon of alternating Mn-II and Mn-III ions surrounding a central Mn-II ion. The remaining ligation is by six bridging and chelating mda(2-) or teaH(2-) groups, and either six terminal N-3(-) (1, 2, 4, 5) or Cl- (3) ions. Each bridging mda(2-) or teaH(2-) ligand contains both mu- and mu(3)-O atoms, resulting in a similar, near-planar [Mn-7(mu(3)-OR)(6)(mu-OR)(6)](5+) core for all three complexes. The Mn-7 anions of 1 and 2 are connected via Na+ cations to yield one-dimensional zigzag chains and three-dimensional windmill-like "hexagons-of-hexagons", respectively. In contrast, the Mn-7 anion of 3 forms a strong hydrogen-bond between the NHEt3+ cation and a terminal Cl- ion giving a discrete ion-pair, Variable-temperature, solid-state direct current (dc) and alternating current (ac) magnetization studies were carded out in the 5.0-300 K range. Fits of dc magnetization versus field (H) and temperature (T) data by matrix diagonalization gave S = 11, g = 1.95, D = -0.15 cm(-1) for 1, S = 16, g = 1.95, D = -0.02 cm(-1) for 2, and S = 11, g = 1.92, D= -0.13 cm(-1) for 3 (D is the axial zero-field splitting parameter). Complexes 4 and 5 were also found to possess S = 11 and S = 16 ground states, respectively. The different ground states of 1 and 2 were rationalized on the basis of the sign and magnitude of the various Mn-2 exchange parameters obtained from density functional theory (DFT) calculations. This analysis confirmed the presence of spin frustration effects, with the ground states being determined by the relative magnitude of the two weakest interactions. The combined results demonstrate the usefulness of N-based dipodal and tripodal alkoxide-based chelates as a route to structurally and magnetically interesting Mn clusters
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Dates et versions

hal-00981994 , version 1 (23-04-2014)

Identifiants

Citer

Theocharis C. Stamatalos, D. Foguet-Albiol, Katye M. Poole, Wolfgang Wernsdorfer, Khalil A. Abboud, et al.. Spin Maximization from S=11 to S=16 in Mn-7 Disk-Like Clusters: Spin Frustration Effects and Their Computational Rationalization. Inorganic Chemistry, 2009, 48 (20), pp.9831-9845. ⟨10.1021/ic901393m⟩. ⟨hal-00981994⟩

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