In this work, a large excess of electrostatic repulsion, arising from the axial ligands, over that from the equatorial ligands is taken as the design strategy for high performance pentagonal bipyramidal (PBP) DyIII single-ion magnets (SIMs).

It is crucial to promote axiality to enhance easy-axis magnetic anisotropy. Two mononuclear Dy compounds, in which each Dy is nine-coordinated, namely, [(CHNO)Dy(NO)(HO)]·CHOH (1) and [(CHNO)Dy(NO)(CHOH)]·HO (2) (HL = N-(2-pyridoyl)-4-pyridinecarboxamidrazone), have been prepared through controlling the amount of CHOH and HO solvents. Geometry modulations were realized by interchanging coordinated and lattice solvents, thus achieving a structure closer to the configuration of a capped square antiprism for 2 compared to that for 1. Notably, magnetic studies revealed that compound 1 displays no slow relaxation of magnetization while compound 2 exhibits single-molecule magnet (SMM) behaviour in the absence of a static magnetic field, with the highest energy barrier (203.11 K) of nine-coordinated Dy SMMs. Ab initio calculations were performed to elucidate such a distinct performance, demonstrating that the combination of the larger charge distribution along the magnetic axis and the lower charge distribution in the equatorial plane generates a strong easy-axis ligand field to enhance magnetic properties, which is further associated with the structural symmetry. In addition, a possible coordination mode is proposed to realize high axis anisotropy for nine-coordinated Dy compounds. This work presents an effective method to modulate the dynamic magnetic relaxation of the Dy SMMs through interchange between coordinated and lattice solvents.

Solvent-tuning changes the magnetic exchange interaction and results in different magnetic relaxation dynamics in Dy2 systems ligated by a μ-phenolato heptadentate Schiff base.

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Here, two Dy(iii) polymorphs with D4d symmetry, [Dy(Clapi)]2·(CH2Cl2)2 (1a and 1b), exhibit distinct magnetic dynamic behaviours. This work presents a rational model to explore the magneto-structural relationship of SMMs in both experimental and theoretical aspects.

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Lattice water effects on the structures and magnetic properties of single-molecule magnets (SMMs) have attracted considerable attention. Herein, we have successfully synthesized two centrosymmetric binuclear compounds [Dy2(2,3′-ppcad)2(C2H3O2)4(H2O)2] (1) and [Dy2(2,3′-ppcad)2(C2H3O2)4(H2O)2]·6H2O...

Nano-hydroxyapatite (nHAp)-based dual-/multi-modal bioimaging systems have received significant attention due to their excellent bioactivity and biocompatibility. However, it is difficult to obtain highly sensitive imaging results. On the one side, the high surface energy of nHAp tends to enable the agglomerations of nHAp, which could further limit the clinical applications. On the other side, the main strategy for the construction of co-doped nHAp nanocrystals depends on high temperature and techniques of post-modification, resulting in inevitable nHAp crystal polymerization and increased particle size. In order to overcome the current shortcomings of nonmonodispersed nHAp, such as uneven distribution and easy aggregation, the construction of monodispersed nHAp is expected to ensure the imaging performance of traceable nHAp by reducing the aggregation of nHAp in vivo and improving the imaging sensitivity. Thus, in this review, the approaches of monodispersed nHAp based on hydrothermal, biomimetic and microwave synthesis methods are summarized. Furthermore, the development of single/multi-mode traceable monodispersed nHAp for biological imaging applications is also discussed.