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 bisbutoxide pentapyridyl dysprosium(III) SMM. The re-hys (@100 Oe s À 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 À 1 regime, we are able to identify that the CÀ F bond related vibration energy of the axial ligand ranging from 200 to 350 cm À 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.

Guanidinate ligand | Magnetic properties | Lanthanides | Single-molecule magnets | Ab initio calculations Two chelating guanidinate-based dysprosium(III) complexes, namely the monomeric {(Me 3 Si) 2 NC(N i Pr) 2 } 2 Dy(μ-Cl) 2 Li(THF) 2 1 and the dimeric [{(Me 3 Si) 2 NC(N iPr) 2 } 2 Dy(μ-Cl)] 2 2, have been confirmed to be single-molecule magnets. Moreover, the alteration from 1 to 2 leads to an obvious mitigated quantum tunnelling of magnetization at zero field of the hysteresis loop and much enhanced magnetic relaxation barrier (up to 312 K). 5% dilution with the yttrium(III) analogue for 2 shows no clear change for the hysteresis, indicating the single-ion nature of the magnetic behavior.

Theoretical calculation plays an important role in the emerging field of single-molecule magnets (SMMs). It can not only explain experimental phenomena but also provide synthetic guidance. This review focuses on discussing the computational methods that have been used in this field in recent years. The most common and effective method is the complete active space self-consistent field (CASSCF) approach, which predicts mononuclear SMM property very well. For bi- and multi-nuclear SMMs, magnetic exchange needs to be considered, and the exchange coupling constants can be obtained by Monte Carlo (MC) simulation, ab initio calculation via the POLY_ANISO program and density functional theory combined with a broken-symmetry (DFT-BS) approach. Further application for these calculation methods to design high performance SMMs is also discussed.

A family of fully sandwiched arachno‐lanthanacarborane complexes formulated as {η6‐[μ‐1,2‐[o‐C6H4(CH2)2]‐1,2‐C2B10H10]2Ln}{Li5(THF)10} (Ln=Tb, Dy, Ho, Er, Y) is successfully synthesized, where the “carbons‐adjacent” carboranyl ligand (arachno‐R2‐C2B10H104−) bears four negative charges and coordinates to the central lanthanide ions using the hexagonal η6C2B4 face. Thus, the central lanthanide cations are pseudo‐twelve‐coordinate and have an approximate pseudo‐D6h symmetry or hexagonal‐prismatic geometry. As the crystal field effect imparted by this geometry is still unknown, we thoroughly investigated the magnetic properties of this series of complexes and found that the crystal field imposed by this ligand causes a relation of Tb>Dy>Ho>Er for the energy gaps between the ground and the first excited states, which is of striking resemblance to the ferrocenophane and phthalocyanine ligands although the latter two ligands give disparate local coordination geometries. Moreover, the effective energy barrier to magnetization reversal of 445(10) K, the observable hysteresis loop up to 4 K and the relaxation time of the yttrium‐diluted sample reaching 193(17) seconds at 2 K under an optimized field for the Tb analogue of this family of arachno‐lanthanacarborane complexes, render a new benchmark for Tb3+‐based single‐molecule magnets.

The syntheses and magnetic properties of organometallic heterometallic compounds [K(THF) 6 ]{Co I [(μ 3 -HAN)RE 2 Cp* 4 ] 2 } (1-RE) and [K(Crypt)] 2 {Co I [(μ 3 -HAN)RE 2 Cp* 4 ] 2 } (2-RE) containing hexaazatrinaphthylene radicals (HAN *3À ) and four rare earth (RE) ions are reported. 1-RE shows isolable species with ligand-based mixed valency as revealed by cyclic voltammetry (CV) thus leading to the isolation of 2-RE via one-electron chemical reduction. Strong electronic communication in mixed-valency supports stronger overall ferromagnetic behaviors in 2-RE than 1-RE containing Gd and Dy ions. Ac magnetic susceptibility data reveal 1-Dy and 2-Dy both exhibit slow magnetic relaxation. Importantly, larger coercive field was observed in the hysteresis of 2-Dy at 2.0 K, indicating the enhanced SMM behavior compared with 1-Dy. Ligand-based mixed-valency strategy has been used for the first time to improve the magnetic coupling in lanthanide (Ln) SMMs, thus opening up new ways to construct strongly coupled Ln-SMMs.