The synthesis of air-stable, high-performance single-molecule magnets (SMMs) is of great significance for their practical applications. Indeed, Ln complexes with high coordination numbers are satisfactorily air stable. However, such geometries easily produce spherical ligand fields that minimize magnetic anisotropy. Herein, we report the preparation of three air-stable eight-coordinate mononuclear Dy(iii) complexes with triangular dodecahedral geometries, namely, [Dy(BPA-TPA)Cl](BPh4)2 (1) and [Dy(BPA-TPA)(X)](BPh4)2·nCH2Cl2 (X = CH3O- and n = 1 for 2; L = PhO- and n = 2 for 3), using a novel design concept in which the bulky heptadentate [2,6-bis[bis(2-pyridylmethyl)amino]methyl]-pyridine (BPA-TPA) ligand enwraps the Dy(iii) ion through weak coordinate bonds leaving only a small vacancy for a negatively charged (Cl-), methoxy (CH3O-) or phenoxy (PhO-) moiety to occupy. Magnetic measurements reveal that the single-molecule magnet (SMM) property of complex 1 is actually poor, as there is almost no energy barrier. However, complexes 2 and 3 exhibit fascinating SMM behavior with high energy barriers (U eff = 686 K for 2; 469 K for 3) and magnetic hysteresis temperatures up to 8 K, which is attributed to the pseudolinear ligand field generated by one strong, highly electrostatic Dy-O bond. Ab initio calculations were used to show the apparent difference in the magnetic dynamics of the three complexes, confirming that the pseudo-mono-axial ligand field has an important effect on high-performance SMMs compared with the local symmetry. This study not only presents the highest energy barrier for a triangular dodecahedral SMM but also highlights the enormous potential of the pseudolinear Dy-L ligand field for constructing promising SMMs.

Taking advantage of the pentaethylene glycol (EO5) and deprotonation of EO5, a family of new structurally hexagonal bipyramidal Dy(III) complexes, [Dy(EO5)(2,6-dichloro-4-nitro-PhO)2](2,6-dichloro-4-nitro-PhO) (1), [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)2] (2), and [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)Cl] (3), were controbllably synthesized and structurally characterized. Magnetic measurements show that complex 1 is a zero-field SIM and has an observable hysteresis opening up to 4 K. Conversely, only under extra magnetic field is slow magnetic relaxation observed in 2 and 3. This considerable difference in the magnetic behavior is mainly caused by the change of the equatorial negative charge. Detailed ab initio calculations further elucidate that the quantum tunneling is induced by the presence of equatorial negative charge, and the magnetic anisotropy depends on the axial ligands. This work demonstrates that the absence of the equatorial negative charge should also be considered in the rational design of promising single molecular magnets based on the oblate ions.

Two mononuclear seven-coordinate Dy(iii) complexes with different strengths of ligand fields exhibit different slow magnetic relaxations.

Na-ion batteries (NIBs) have attracted more and more attention due to the plentiful resources of sodium, excellent ion storage capacity and superior cycle life. However, the implementation of NIBs has been limited by the shortage of electrode materials with outstanding comprehensive properties. Among the discovered anode materials, transition metal sulfides (TMSs) have been widely considered as one of the most competitive and promising ones due to their high theoretical specific capacity. Herein, CoS2 nanoparticles embedded in nitrogen-doped carbon nanosheets (CoS2/NC) were designed and synthesized by using Co-based Metal-organic frame-work (Co-MOF) as precursor of metal sulfurs, followed by a simple combined carbonization-sulfurization process. The CoS2/NC compo-sites were evaluated as binder-free anode materials for NIBs, delivering a high reversible gravimetric capability of 332 mA h g(-1) after 60 cycles as well as great rate capability of 326.6 mA h g(-1) at 2000 mA g(-1). The improvement of electrochemical behavior is attributed to the synergistic interaction between CoS2 nanoparticles with high electro-chemical activity and the sheet-shaped N-doped carbon with high conductivity. This work provides a greatly attractive strategy for energy conversion and storage.