Abstract
The coordination chemistry of dysprosium and terbium toward phosphine and arsine oxides was further explored. Thus, the new nitrate [M(NO3)3(Ph3PO)3] (M = Tb, 1; Dy, 2), [Dy(NO3)3(EtOH)(Ph3XO)2] (X = P, 3; As, 4), chloride [DyCl2(Ph3AsO)4]Cl (5), triflate [Dy(OTf)2(MePh2PO)4]OTf (6; OTf = triflate) and hexafluoroacetylacetonate [M(hfa)3(Ph3PO)2] (hfa = hexafluoroacetylacetonate; M = Tb, 7; Dy, 8) complexes were isolated and fully characterized. The crystal structures of 1·CH3CN, 2·CH3CN, 4, 5·2.75EtOH·1.25H2O, 6, 7, and 8 show MO9 cores in 1, 2, and 4, with highly distorted geometry, between spherical capped square antiprism and muffin-like, hexacoordinated environments for the dysprosium ions in 5 and 6, with octahedral geometry, and octa-coordination for the lanthanoid metals in 7 and 8, with geometry closer to square antiprism. Comparison of the magnetic behavior of all the complexes allows analyzing which metal ion (Tb or Dy), phosphine or arsine oxide, or anionic ligand favor more the slow relaxation of the magnetization. Alternating current magnetic measurements show that only 2, 4, and 8 present slow relaxation of the magnetization in the presence of an external magnetic field, 8 being the complex with the highest Ueff (44.85 K) of those described herein.
Highlights
The observation for the first time of slow magnetic relaxation in mononuclear lanthanoid complexes (TBA)[Pc2Ln] (TBA = But4N+; Pc = phthalocyanide; LnIII = Tb or Dy) (Ishikawa et al, 2003) provided a real breakthrough in molecular magnetism, opening the field of single ion magnets (SIMs) in 2003
Similar pentagonal bipyramidal complexes were not reported for Ph3PO, what would lead to evaluate the influence of the aromatic vs. the aliphatic ring in the magnetic behavior of the complexes
With these considerations in mind, different dysprosium and/or terbium salts were initially mixed with Ph3XO (X = P or As) or MePh2PO in 1:2 molar ratio, with the intention of isolating complexes of stoichiometry Ln(R3XO)2Y5 (R3 = Ph3 or MePh2; X = P or As; Y = OH2 and/or monodentate anion)
Summary
The observation for the first time of slow magnetic relaxation in mononuclear lanthanoid complexes (TBA)[Pc2Ln] (TBA = But4N+; Pc = phthalocyanide; LnIII = Tb or Dy) (Ishikawa et al, 2003) provided a real breakthrough in molecular magnetism, opening the field of single ion magnets (SIMs) in 2003. Rinehart and Long published in 2011 (Rinehart and Long, 2011) a benchmark study where they provided a clear explanation of how the electronic structure of f-elements can in theory be manipulated to create new single molecule magnets (SMMs) In this study, they give the relationship between the coordination environment of lanthanoid ions and the magnetic anisotropy of the complex and, they suggest that one can match an appropriate ligand field to maximize magnetic anisotropy on the basis of the shapes (oblate or prolate) of the 4f-shell electron density distributions. For the oblate Tb(III) and Dy(III) ions, theoretical calculations
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