L.B.

Two Dy compounds, [Dy₂(Phen)₂(CH₃COO)₆] (1; Phen = 1,10-phenanthroline) and [Dy(Phen)₂(NO₃)₃] (2), were obtained by the reactions of Phen with different dysprosium salts containing different anions, which act as bridging groups and greatly affect the coordination polyhedra of the metal ions. In the former complex, the Dy^III ions are bridged by acetate anions and adopt a spherical capped square antiprismatic (C_4v) coordination environment, whereas a bicapped square antiprism (D_4d) was observed for 2, in which the Dy^III ions are bridged by nitrate anions. Static and dynamic magnetic measurements revealed that both compounds display slow magnetic relaxation but with fast quantum tunneling of magnetization (QTM). In an applied direct-current (dc) field, the QTM was suppressed, and two slow magnetic relaxation processes occurred for both compounds. Comparative studies on the magnetic properties indicate how the ligand field and the local geometric symmetry of the magnetic anisotropy of the Dy^III center leads to differing magnetic behavior.

Two Dy compounds, [Dy₂(Phen)₂(CH₃COO)₆] (1, Phen = 1,10-phenanthroline) and [Dy(Phen)₂(NO₃)₃] (2), are obtained. The coordination geometries of the Dy^III ions in 1 and 2 are C_4v and D_4d, respectively. Static and dynamic magnetic measurements reveal that both of them display two-step thermal magnetic relaxation under an external direct-current (dc) field and show single-molecule magnetism.

Invited for the cover of this issue is the group of Ming-Liang Tong at the Sun Yat-Sen University and collaborators in France, China, and Belgium. The image depicts the magnetic hysteresis and the fluorescence of a pentagonal bipyramidal Dy^III single-ion magnet. Read the full text of the article at 10.1002/chem.201606029.

“We are most excited about the discovery of the fluorescence fine structure in this system.” Read more about the story behind the cover in the Cover Profile and about the research itself on page ▪▪ ff. (DOI: 10.1002/chem.201606029).

Heterometallic Gd−Pt complexes ([Gd₂Pt₃(H₂O)₂(SAc)₁₂] (SAc=thioacetate), [Y_1.4Gd_0.6Pt₃(H₂O)₂(SAc)₁₂], and [Gd₂Pt₃(H₂O)₆(SAc)₁₂]⋅7 H₂O have been synthesized. The crystal structures and DFT calculations indicated a Gd−Pt heretometallic bond. Single-crystal ESR spectra determined the direction of magnetic anisotropy as direction of the Gd−Pt bond. In other words, the Gd−Pt bond dictates the direction of magnetic anisotropy. The heterometallic Gd−Pt bond lowers the symmetry of the Gd ion, splitting the Kramers doublet in a dc field. Thus, we observed clear field-induced slow magnetic relaxation of [Y_1.4Gd_0.6Pt₃(H₂O)₂(SAc)₁₂] up to 36 K. The relaxation process was determined to be a direct process.

Relax and go slow! A new strategy is reported in which a diamagnetic Pt ion was used as a ligand on a Gd ion to bring about SMM-like behavior in a Gd complex. The heterometallic Gd−Pt bond lowers the symmetry of the Gd ion, splitting the Kramers doublet in a dc field. Thus, the complexes should undergo slow magnetic relaxation.

The pentagonal bipyramidal single-ion magnets (SIMs) are among the most attractive prototypes of high performance single-molecule magnets (SMMs). A fluorescence-active phosphine oxide ligand is introduced, and by combining dynamic magnetic measurements, optical characterization, and ab initio calculations, the magneto-optical correlation of a high-performance pseudo-D_5h Dy^III SIM with large U_eff = 508(2) K and high magnetic hysteresis temperature of 19 K, [Dy(CyPh₂PO)₂(H₂O)₅]Br₃⋅2 (CyPh₂PO)⋅EtOH⋅3 H₂O (CyPh₂PO= cyclohexyl(diphenyl)phosphine oxide) was studied. This work provides a deeper insight into the rational design of promising molecular magnets. More information can be found in the Full Paper by M.-L. Tong, J.-L. Liu, et al. (DOI: 10.1002/chem.201606029).

A new synthetic procedure was developed to obtain a novel mononuclear chiral square-pyramidal (acetato)bis(aminoalkoxido)Mn^III complex from a heterometallic Zn^II/Mn^II system with a crucial role for O₂ in the process. The resulting compound was characterized spectroscopically and crystallographically, and its magnetic properties were determined. The Mn^III ion exhibits magnetic anisotropy with a zero-field splitting D parameter equal to –2.95 cm^–1.

A new synthetic procedure is developed to obtain a novel mononuclear chiral square-pyramidal (acetato)bis(aminoalkoxideo)Mn^III complex. The resulting compound is characterized spectroscopically and crystallographically, and its magnetic properties are determined.

Assembly of the triangular, organic radical-bridged complexes Cp*₆Ln₃(μ₃-HAN) (Cp*=pentamethylcyclopentadienyl; Ln=Gd, Tb, Dy; HAN=hexaazatrinaphthylene) proceeds through the reaction of Cp*₂Ln(BPh₄) with HAN under strongly reducing conditions. Significantly, magnetic susceptibility measurements of these complexes support effective magnetic coupling of all three Ln^III centers through the HAN^3−. radical ligand. Thorough investigation of the Dy^III congener through both ac susceptibility and dc magnetic relaxation measurements reveals slow relaxation of the magnetization, with an effective thermal relaxation barrier of U_eff=51 cm⁻¹. Magnetic coupling in the Dy^III complex enables a large remnant magnetization at temperatures up to 3.0 K in the magnetic hysteresis measurements and hysteresis loops that are open at zero-field up to 3.5 K.

A Dy^III HAT Trick: Magnetic coupling between three lanthanide ions is established through a central organic radical bridging ligand in Cp*₆Ln₃(μ₃-HAN) (Cp*=pentamethylcyclopentadienyl; Ln=Gd, Tb, Dy; HAN=hexaazatrinaphthylene). Coupling in the Dy^III congener enables a large remnant magnetization up to 3.0 K in the magnetic hysteresis measurements and hysteresis loops that are open at zero-field up to 3.5 K.

The cover picture shows space-filling plots of two enantiomeric Mn^III triangles and their electronic circular dichroism (ECD) spectra against a background featuring an enantiomeric image from the macroscopic world. Details are discussed in the article by A. Escuer et al. on page 991 ff (DOI: 10.1002/ejic.201601138). For more on the story behind the cover research, see the Cover Profile (DOI: 10.1002/ejic.201700078).

Three molecular structures, each containing three different lanthanide(III) centres, have been prepared by coupling three kinetically inert lanthanide(III) complexes in an Ugi reaction. These 2 kDa molecules were purified by dialysis and characterised by NMR and luminescence techniques. The photophysical properties of these heterotrimetallic complexes were investigated and are discussed by comparison with simpler, but related, heterodimetallic compounds. It was found that an aminonaphthalene unit inhibits the sensitisation of terbium, and that the spatial arrangement of the chromophores and lanthanide(III) centres in these molecules inhibits the efficient sensitisation of europium. We conclude that the intramolecular collisions required for efficient Dexter energy transfer from the sensitiser to the lanthanide(III) centre can be prevented by steric congestion.

We have prepared large distinct heteronuclear lanthanide architectures from kinetically inert building blocks. By combining optical and magnetic resonance spectroscopy, we are able to conclude that conformational freedom allowing for intramolecular collision is more important than apparent proximity for efficient energy transfer.