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Herein the synthesis, structural characterization, and magnetic properties of a Pr(IV) complex [Pr(OSiPh3)4(L)] (1, L = 4,4′-dimethoxy-2,2′-bipyridine) are reported. The stability of the Pr(IV) complex significantly enhanced with the use of the bidentate ligand L. Slow magnetic relaxation was observed at low temperatures, indicating that the complex may be the first single-ion magnet with a tetravalent lanthanide ion being the magnetic center. [ABSTRACT FROM AUTHOR]

Although the development of single‐molecule magnets (SMMs) is rapid, there are only two families of high energy barrier (Ueff) dysprosium(III) SMMs known so far: the cyclopentadienyl (Cp) family with a sandwich structure and the pentagonal‐bipyramidal (PB) family with D5h symmetry. These high‐barrier SMMs, which usually possess Ueff>500 cm−1 allow the separate study of the four magnetic relaxation paths, namely, direct, quantum tunnelling, Raman and Orbach processes, in detail. Whereas the first family is chemically more challenging to modify the Cp rings, it is shown herein that the latter family, with the common formulae [DyX1X2(Leq)5]+, such as X1/X2=−OCMe3, −OSiMe3, −OPh, Cl− or Br−; Leq=THF/pyridine/4‐methylpyridine, can be readily fine‐tuned with a range of axial and equatorial ligands by simple substitution reactions. This allows unambiguous confirmation that the Ueff mainly depends on the identity of X1 and X2, rather than on Leq. More importantly, the fitted parameters are barrier dependent. If X1 is an O donor and X2 is a halide, 500

We present a controlled synthetic route to optimize the equatorial coordination environment of three Dy(III) borohydride complexes: Dy(BH4)3(THF)3 (1), [Dy(BH4)2(THF)5][BPh4] (2) and [Dy(BH4)2(18-C-6)][Na(THF)2(18-C-6)][BPh4]2 (3) (THF = tetrahydrofuran, BPh4− = tetraphenyl borate, 18-C-6 = 18-crown-6-ether), which have the same axial coordination environment, while different equatorial sites. Alteration of the coordination environment on the equatorial sites leads to a significant change in their magnetic properties. In the absence of the dc field, complex 1 with three THF molecules and one BH4− ligand in the equatorial plane shows no single-molecule magnet (SMM) behaviour, complex 2 having five THF molecules at equatorial sites displays small tails of out-of-phase (χ′′) signals, and complex 3 containing one 18-C-6 with six O atoms in the equatorial plane exhibits χ′′ signals at higher temperatures. These results show the optimization of the equatorial coordination environment of Dy(III) mononuclear single-molecule magnets. [ABSTRACT FROM AUTHOR]

Eight‐coordinated DyIII centres with D6h symmetry are expected to act as high‐performance single‐molecule magnets (SMMs) due to the simultaneous fulfilment of magnetic axiality and a high coordination number (a requisite for air stability). But the experimental realization is challenging due to the requirement of six coordinating atoms in the equatorial plane of the hexagonal bipyramid; this is usually too crowded for the central DyIII ion. Here a hexaaza macrocyclic Schiff base ligand and finetuned axial alkoxide/phenol‐type ligands are used to show that a family of hexagonal bipyramidal DyIII complexes can be isolated. Among them, three complexes possess nearly perfect D6h local symmetry. The highest effective magnetic reversal barrier is found at 1338(3) K and an open hysteresis temperature of 6 K at the field sweeping rate of 1.2 mT s−1; this represents a new record for D6h SMMs. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) layer CuII compound [Cu3(L)2(N3)4] ( 1) [L = 2-amino-3-(5-tetrazole)-methyate- N-pyridine] was synthesized by in-situ hydrothermal reaction of CuCl2 ·2H2O, NaN3, and 3-(5-tetrazole)-methyate- N-pyridine. The central Cu1 and Cu2 atoms are located in five-coordinate and six-coordinate arrangements, respectively. Three CuII ions are linked by mixed double EO (end-on)-azido-tetrazole bridges to give trinuclear CuII clusters, which are further extended by EE (end-to-end) azido bridges to form 2D metal-organic layers. The magnetic exchange interactions in complex 1 were investigated by DFT calculations, and the calculated exchange interaction ( J = -849 cm-1) revealed that the double EO-azido-tetrazole bridges transmit antiferromagnetic coupling between CuII ions. [ABSTRACT FROM AUTHOR]