Three Gd-Based Metal-Organic Frameworks Constructed from Similar Dicarboxylate Ligands with Large Magnetic Entropy Changes

Magnetic cooling: a molecular perspective

The magnetocaloriceffect is considered as an energy-efficient and environmentally friendly technique which can take cooling technology to the next level. Apart from its commercial application at room temperature, magnetic refrigeration is an up-and-coming solution for the cryogenic regime, especially as an alternative to He³ systems. Molecular magnets reveal advantageous features for ultra-low cooling which are competitive with intermetallic and lanthanide alloys. Here, we present a guide to the current status of magnetocaloric effect research of molecular magnets with a theoretical background focused on the inverse magnetocaloric effect and an overview of recent results and developments, including the rotating magnetocaloric effect.

Preparation and characterization of two lanthanide complexes with one-dimensional chain-like structures

Two novel RE–Hg (RE = rare earth) complexes [RE(IA)3(H3O)2]2 n·2 n(HgCl4)· n(HgCl5)· nH2O·3 nH3O (RE = Y, 1; Lu, 2; IA = isonicotinic acid anion) were synthesized through hydrothermal reactions and are structurally characterized by single-crystal X-ray diffraction. The two complexes are isostructures and are characteristic of a one-dimensional chain-like structure. Both complexes are characterized by a three-dimensional supramolecular network. Photoluminescence experiments using solid-state samples show that they possess emission bands in the blue or red region. They have remarkable CIE chromaticity coordinates of (0.1172, 0.182) and (0.623, 0.3765), respectively. As a result, they are potential candidates for light-emitting materials for light-emitting diodes. They show wide optical band gaps of 3.29 eV and 2.89 eV, as revealed by the solid-state UV/Vis diffuse reflectance spectra.

Synthesis, structure, photophysical properties, and energy transfer mechanism of an erbium–mercury compound

A hydrothermal reaction leads to the formation of a novel erbium–mercury compound [Er(IA)3(H3O)(H2O)] n(0.5 nHg2I6) (1) (HIA = isonicotinic acid). The compound has been characterized by single-crystal X-ray diffraction. It is characteristic of a one-dimensional chain-like structure and a two-dimensional supramolecular layer. A solid-state photoluminescence experiment reveals that this compound displays upconversion green photoluminescence. The photoluminescence emission peaks can be attributed to the 4 G11/2 → 4 I15/2, 4 F7/2 → 4 I15/2, and 2 H11/2 → 4 I15/2 of the Er3+ ions. The energy transfer mechanism is consistent with the energy-level diagrams of the erbium ions and isonicotinic acid ligand. This compound possesses Commission Internationale de I'Éclairage chromaticity coordinates of 0.1755 and 0.5213. A solid-state diffuse reflectance measurement reveals that this compound features a narrow optical band gap of 1.97 eV.

Photophysical properties and energy transfer mechanism of a praseodymium compound with a two-dimensional layer

A hydrothermal reaction results in the formation of a novel [Pr2(2,5-PA)2(2,5-HPA)2(H2O)4] n·2 nH2O complex (2,5-H2PA = 2,5-pyridinedicarboxylic acid). The complex is structurally characterized by single-crystal X-ray diffraction and crystallizes in the space group P21 of the monoclinic system with two formula units in one cell. This praseodymium complex is characterized by a two-dimensional layered structure. A solid-state photoluminescence experiment reveals that the praseodymium complex shows an emission in the red region. The complex has Commission Internationale de I’Éclairage chromaticity coordinates of 0.5495 and 0.4492. The photoluminescence emission bands could be assigned to the characteristic emission of the 4 f electron intrashell transition of the 3 P0 → 3 H5, 1 D2 → 3 H4, 3 P0 → 3 H6, 3 P0 → 3 F2, and 3 P1 → 3 F3 of the Pr3+ ions. The energy transfer mechanism is explained by the energy level diagrams of the praseodymium ions and the 2,5-H2PA ligand. A solid-state diffuse reflectance measurement shows that the complex possesses a wide optical band gap of 3.48 eV.

Two GdIII complexes with different structures and magnetocaloric properties induced by metal ion sources

Two 0D/3D Gd^III complexes based on dl-malic acid have been constructed and they display weak ferromagnetic behaviors and significant MCEs.

Large magnetocaloric effect and remarkable single-molecule-magnet behavior in triangle-assembled LnIII6 clusters

Two intriguing triangle-assembled LnIII6 clusters (1 and 2) have been synthesized. The magnetic study reveals that 1 displays a larger cryogenic magnetocaloric effect, while 2 exhibits remarkable SMM behaviors.

Linear-shaped LnIII4 and LnIII6 clusters constructed by a polydentate Schiff base ligand and a β-diketone co-ligand: structures, fluorescence properties, magnetic refrigeration and single-molecule magnet behavior

A series of linear-shaped LnIII4 and LnIII6 clusters were synthesized. The structures, fluorescence properties and magnetic properties have been deeply studied.

Structures, fluorescence properties and magnetic properties of a series of rhombus-shaped LnIII4 clusters: magnetocaloric effect and single-molecule-magnet behavior

A family LnIII4 clusters were successfully synthesized and structurally characterized. Magnetic studies show that Gd₄ cluster displays magnetic refrigeration, while Dy₄ cluster demonstrates two distinct slow magnetic relaxation processes.

Controlled Gelation of Graphene Towards Unprecedented Superstructures

Graphene exhibits a range of exceptional physical properties and holds great promise for development of novel bulk materials for widespread applications. Properly engineering of assembled structures of graphene at multiple length scales is essential to realize its full potential in bulk forms. In this Concept article, we highlight the unique colloidal and gelation behavior of a commonly used precursor for graphene, graphene oxide (GO), and discuss how the colloidal chemistry of GO and reduced GO can enable new scalable and cost-effective approaches to construct graphene-based soft superstructures with excellent properties.