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Rare-earth-containing materials featuring rare-earth–chalcogen (RE–E) coordination are of interest as optical and magnetic materials with enhanced properties over their counterparts with O-coordination. Herein, a series of rare-earth chalcogenidotetrachloride complexes of the general formula [η5-Cp*RE(μ-Cl)(THF)]3(μ3-Cl)(μ3-E) (RE3ECl4: RE = Dy, Gd, Y; E = S, Se, Te; Cp* = pentamethylcyclopentadienide) were reported. Apart from for the identity of the rare-earth and chalcogen elements, these clusters share a common core motif composed of triangularly arranged RE atoms with one chloro ligand bridging each neighboring pair of RE atoms; the trimetallic plane is additionally capped by triply bridging chloro and chalcogenide ligands, one for each kind. Each RE atom is further coordinated with one Cp* and one THF ligand. Comparative magnetic and luminescence studies revealed fine but definitive differences due to using different metal and chalcogen elements. Experimental and computational studies have been used to gain insights into the dipolar and super-exchange interactions for the magnetically active Dy- and Gd-based clusters. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Many sandwich‐type lanthanide complexes show extremely high energy barriers (Ueff) for the reversal of magnetization and high blocking temperatures, being the star molecules in the research area of single‐molecule magnets. Herein, the preparation, structural determination, and magnetic property studies of two ansa‐bridged Er‐COT (COT = cyclooctatetraenyl dianion) complexes [KDME2][Er((η8‐COT‐SiMe2)2O)] (1) and [KDME2][Er((η8‐COT‐SiiPr2)2O)]K[Er((η8‐COT‐SiiPr2)2O)] (2) were reported. The Er(III) ions in both complexes are sandwiched by two COT rings which are ansa‐bridged by a [Si‐O‐Si] group. Magnetic studies reveal both complexes display slow magnetic relaxations with comparable energy barriers (228(5) K for 1, and 196(4) K for 2) and blocking temperatures (10.5 K for both complexes). The difference in the relaxation times (τ) for the two complexes was studied in details: different molecular vibrations induced by the substituents are the main reason for τ for 1 being about 10 times longer than for 2 at the same temperature above 10 K, while the quantum tunnelling of magnetization relaxation time (τQTM) for 2 is about 10 times longer than for 1 below 8 K, probably owing to the different dipolar interactions. Further rearrangement of molecular network with such ansa‐bridged SMMs is promising to design molecular magnetic materials with enhanced properties or new properties. [ABSTRACT FROM AUTHOR]

Magnetic semiconductors, with integrated properties of ferromagnets and semiconductors, are significant for developing next‐generation spintronic devices. Herein two atomically precise clusters of dysprosium(III) tellurides, formulated respectively as [Na2(15‐crown‐5)3(py)2][(η5‐Cp*Dy)5(Te)6](py)4 (Dy5Te6, Cp*=pentamethylcyclopentadienyl; py=pyridine) and [K(2,2,2‐cryptand)]2[(η5‐Cp*Dy)6(Te3)(Te2)2(Te)3] (Dy6Te10), are reported. Crystallographic studies revealed the presence of multifarious tellurido ligands within the polyhedral cluster cores. Spectroscopic and magnetic studies showed that both clusters are single‐molecule magnets exhibiting slow magnetic relaxation behaviors at low temperatures and semiconductors with low optical band gaps comparable to benchmark semiconductors. These clusters represent probably the first lanthanide‐based molecular magnetic semiconductors. [ABSTRACT FROM AUTHOR]

The fast Raman relaxation process via a virtual energy level has become a puzzle for how to chemically engineer single‐molecule magnets (SMMs) with better performance. Here, we use the trifluoromethyl group to systematically substitute the methyl groups in the axial position of the parent bis‐butoxide pentapyridyl dysprosium(III) SMM. The resulting complexes—[Dy(OLA)2py5][BPh4] (LA=CH(CF3)2−1, CH2CF3−2, CMe2CF3−3)—show progressively enhanced TBhys (@100 Oe s−1) from 17 K (for 3), 20 K (for 2) to 23 K (for 1). By experimentally identifying the varied under barrier relaxation energy in the 5–500 cm−1 regime, we are able to identify that the C−F bond related vibration energy of the axial ligand ranging from 200 to 350 cm−1 is the key variant for this improvement. Thus, this finding not only reveals a correlation between the structure and the Raman process but also provides a paradigm for how to apply the vibronic barrier model to analyze multi‐phonon relaxation processes in lanthanide SMMs. [ABSTRACT FROM AUTHOR]

Three six‐coordinate DyIII single‐molecule magnets (SMMs) [Dy(OtBu)2(L)4]+ with local D4h symmetry are obtained by optimizing the equatorial ligands. One of the compounds with L=4‐phenylpyridine shows an energy barrier (Ueff) of 2075(11) K, which is the third largest Ueff, and the first Ueff>2000 K for SMMs with axial‐type symmetry so far. Ab initio analysis indicates that the exceptional uniaxial magnetic anisotropy is deeply related to the axially compressed octahedral geometry. This work provides a new insight into the local D4h symmetry for high‐performance SMMs. [ABSTRACT FROM AUTHOR]

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]