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Lanthanide permanent magnets are widely used in applications ranging from nanotechnology to industrial engineering. However, limited access to the rare earths and rising costs associated with their extraction are spurring interest in the development of lanthanide‐free hard magnets. Zero‐ and one‐dimensional magnetic materials are intriguing alternatives due to their low densities, structural and chemical versatility, and the typically mild, bottom‐up nature of their synthesis. Here, we present two one‐dimensional cobalt(II) systems Co(hfac)2(R‐NapNIT) (R‐NapNIT=2‐(2′‐(R‐)naphthyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide, R=MeO or EtO) supported by air‐stable nitronyl nitroxide radicals. These compounds are single‐chain magnets and exhibit wide, square magnetic hysteresis below 14 K, with giant coercive fields up to 65 or 102 kOe measured using static or pulsed high magnetic fields, respectively. Magnetic, spectroscopic, and computational studies suggest that the record coercivities derive not from three‐dimensional ordering but from the interaction of adjacent chains that compose alternating magnetic sublattices generated by crystallographic symmetry. [ABSTRACT FROM AUTHOR]

For a long time, the cobalt(II) complex ([Co(napy)4](ClO4)2) (napy=1, 8‐naphthyridine) has been considered as an eight‐coordinate complex without any structural proof. After careful considerations, two complexes [Co(napy)2Cl2] (1) and [Co(napy)4](ClO4)2 (2) based on the bidentate ligand napy were synthesized and structurally characterized. X‐ray single‐crystal structural determination showed that the cobalt(II) center in [Co(napy)2Cl2] (1) is four‐coordinate with a tetrahedral geometry (Td), while [Co(napy)4](ClO4)2 (2) is seven‐coordinate rather than eight‐coordinate with a capped trigonal prism geometry (C2v). Direct‐current (dc) magnetic data revealed that complexes 1 and 2 possess positive zero‐field splitting (ZFS) parameters of 11.08 and 25.30 cm−1, respectively, with easy‐plane magnetic anisotropy. Alternating current(ac) susceptibility measurements revealed that both complexes showed slow magnetic relaxation behaviour. Theoretical calculations demonstrated that the presence of easy‐plane magnetic anisotropy (D>0) for complexes 1 and 2 is in agreement with the experimental data. Furthermore, these results pave the way to obtain four‐coordinate and seven‐coordinate cobalt(II) single‐ion magnets (SIMs) by using a bidentate ligand. [ABSTRACT FROM AUTHOR]

By using paramagnetic [Fe(CN)6]3− anions in place of diamagnetic [Co(CN)6]3− anions, two field‐induced mononuclear single‐molecular magnets, [Nd(18‐crown‐6)(H2O)4][Co(CN)6]⋅2 H2O (1) and [Nd(18‐crown‐6)(H2O)4][Fe(CN)6]⋅2 H2O (2), have been synthesized and characterized. Single‐crystal X‐ray diffraction analysis revealed that compounds 1 and 2 were ionic complexes. The NdIII ions were located inside the cavities of the 18‐crown‐6 ligands and were each bound by four water molecules on either side of the crown ether. Magnetic investigations showed that these compounds were both field‐induced single‐molecular magnets. By comparing the slow relaxation behaviors of compounds 1 and 2, we found significant differences between the direct and Raman processes for these two complexes, with a stronger direct process in compound 2 at low temperatures. Complete active space self‐consistent field (CASSCF) calculations were also performed on two [Nd(18‐crown‐6)(H2O)4]3+ fragments of compounds 1 and 2. Ab initio calculations showed that the magnetic anisotropies of the NdIII centers in complexes 1 and 2 were similar to each other, which indicated that the difference in relaxation behavior was not owing to the magnetic anisotropy of NdIII. Our analysis showed that the magnetic interaction between the NdIII ion and the low‐spin FeIII ion in complex 2 played an important role in enhancing the direct process and suppressing the Raman process of the single‐molecular magnet. [ABSTRACT FROM AUTHOR]

A family of four mononuclear DyIII β‐diketonate complexes with formulas [Dy(tmhd)3(Br2‐bpy) (1), [Dy(tmhd)3(Br‐bpy)] (2), [Dy(tmhd)3(dppz)] (3), and [Dy(tmhd)3(mcdpq)] (4) (tmhd=2,2,6,6‐tetramethyl‐3,5‐heptanedione, Br2‐bpy=5,5′‐dibromo‐2,2′‐bipyridine, Br‐bpy=5‐bromo‐2,2′‐bipyridine, dppz=dipyrido [3,2‐a:2′,3′‐c]phenazine, mcdpq=2‐methoxyl‐3‐cyanodipyrido[3,2‐f:2,3′‐h]quinoxaline) were prepared by modifying the capping N‐donor coligands. DyIII centers in these complexes feature an N2O6 octacoordinate environment with distorted square‐antiprismatic D4d symmetry. Magnetic investigations evidenced single‐ion magnet behavior in all complexes with energy barriers Ueff of 42.10 (1), 61.47, (2), 77.53 (3), and 2.51 K (4) in the absence of static field, as well as 206.03 (1), 224.13 (2), 247.76 (3), and 49.70 K (4) under applied dc field (Hdc=1500 Oe for 1 and 2; Hdc=1200 Oe for 3 and 4). The different natures of the N‐donor ligands induce changes in both the coordination geometry and their intermolecular interactions, which severely impact their magnetic dynamics. The disparities in their magnetic behaviors and the uniaxial anisotropies are also explained and substantiated by theoretical calculations. Cap variations: A combination of electron‐donating β‐diketonate ligands and different capping N‐donor coligands led to a family of four mononuclear DyIII complexes exhibiting nearly identical D4d symmetry but differing magnetic dynamics, which were elucidated by a combination of magnetic investigations and ab initio calculations. [ABSTRACT FROM AUTHOR]

A series of bis-pentamethylcyclopentadienyl-supported Dy complexes containing different ancillary ligands were synthesized and characterized. Magnetic studies showed that 1 Dy [Cp*2DyCl(THF)], 1 Dy' [Cp*2DyCl2K(THF)] n, 2 Dy [Cp*2DyBr(THF)], 3 Dy [Cp*2DyI(THF)] and 4 Dy [Cp*2DyTp] (Tp=hydrotris(1-pyrazolyl)borate) were single-ion magnets (SIMs). The 1D dysprosium chain 1 Dy' exhibited a hysteresis at up to 5 K. Furthermore, 3 Dy featured the highest energy barrier (419 cm−1) among the complexes. The effects of ancillary ligands on single-ion magnetic properties were studied by experimental, ab initio calculations and electrostatic analysis methods in detail. These results demonstrated that the QTM rate was strongly dependent on the ancillary ligands and that a weak equatorial ligand field could be beneficial for constructing Dy-SIMs. [ABSTRACT FROM AUTHOR]

In recent years, plentiful lanthanide-based (TbIII, DyIII, and ErIII) single-molecule magnets (SMMs) were studied, while examples of other lanthanides, for example, TmIII are still unknown. Herein, for the first time, we show that by rationally manipulating the coordination sphere, two thulium compounds, 1[(Tp)Tm(COT)] and 2[(Tp*)Tm(COT)] (Tp=hydrotris(1-pyrazolyl)borate; COT=cyclooctatetraenide; Tp*=hydrotris(3,5-dimethyl-1-pyrazolyl)borate), can adopt the structure of non-Kramers SMMs and exhibit their behaviors. Dynamic magnetic studies indicated that both compounds showed slow magnetic relaxation under dc field and a relatively high effective energy barrier (111 K for 1, 46 K for 2). Magnetic diluted 1 a[(Tp)Tm0.05Y0.95(COT)] and 2 a[(Tp*)Tm0.05Y0.95(COT)] even exhibited magnetic relaxation under zero dc field. Relativistic ab initio calculations combined with single-crystal angular-resolved magnetometry measurements revealed the strong easy axis anisotropy and nearly degenerated ground doublet states. The comparison of 1 and 2 highlights the importance of local symmetry for obtaining Tm SMMs. [ABSTRACT FROM AUTHOR]

A series of bis‐pentamethylcyclopentadienyl‐supported dysprosium complexes containing different ancillary ligands was studied. The results showed that a weak equatorial ligand field was beneficial for constructing dysprosium single‐ion magnets. More information can be found in the Full Paper by Y. Q. Zhang, B. W. Wang, S. Gao et al. on page 12724. [ABSTRACT FROM AUTHOR]