Recent development in 2D materials beyond graphene

The use of 3d metals in de/hydrogenation catalysis has emerged as a competitive field with respect to “traditional” precious metal catalyzed transformations. The introduction of functional pincer ligands that can store protons and/or electrons as expressed by metal–ligand cooperativity and ligand redox-activity strongly stimulated this development as a conceptual starting point for rational catalyst design. This review aims at providing a comprehensive picture of the utilization of functional pincer ligands in first-row transition metal hydrogenation and dehydrogenation catalysis and related synthetic concepts relying on these such as the hydrogen borrowing methodology. Particular emphasis is put on the implementation and relevance of cooperating and redox-active pincer ligands within the mechanistic scenarios.

First-Row Transition Metal (De)Hydrogenation Catalysis Based On Functional Pincer Ligands.

The observation of spin crossover with thermal hysteresis loops of more than a few Kelvin remains relatively uncommon and unpredictable, so is a relatively underdeveloped, but important, area of spin crossover, particularly for memory applications. Lessons learnt regarding the origins, and the practicalities of the proper study and reporting, of thermal hysteresis loops are considered and explained, from a synthetic chemists perspective, after a general introduction to the field of spin crossover.

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Spin crossover with thermal hysteresis: practicalities and lessons learnt.

Two-dimensional (2D) nanomaterials, especially the inorganic ultrathin nanosheets with single or few-atomic layers, have been extensively studied due to their special structures and rich physical properties coming from the quantum confinement of electrons. With atomic-scale thickness, 2D nanomaterials have an extremely high specific surface area enabling their surface phase to be as important as bulk counterparts, and therefore provide an alternative way of modifying the surface phase for engineering the intrinsic physical properties of inorganic 2D nanomaterials. In this review, we focus on recent research concerning surface chemical modification strategies to effectively engineer the intrinsic physical properties of inorganic 2D nanomaterials. We highlight the newly developed regulation strategies of surface incorporation, defect engineering, and structure modulation of inorganic 2D nanomaterials, which respectively influence the intrinsic conductivity, band structure, and magnetism while maintaining the primary 2D freestanding structures that are vital for 2D based ultrasensitive electronic response, enhanced catalytic and magnetocaloric capabilities.

Surface chemical-modification for engineering the intrinsic physical properties of inorganic two-dimensional nanomaterials.

Molecular magnetism, quo vadis? A historical perspective from a coordination chemist viewpoint☆

Spin-crossover in cobalt(II) compounds containing terpyridine and its derivatives

Molecularly-thin nanosheets are ultimate two-dimensional (2D) nanomaterials potentially giving unusual physical and chemical properties due to the strong 2D quantum and surface effects. Here, it is demonstrated that 1.5-nm-thick ZnO nanosheets exhibit greatly enhanced room-temperature ferromagnetism. Saturation magnetization value of the nanosheets with intercalated dodecyl sulfate layers is approximately 100 times that of ZnO mesocrystals. Anion exchange with dodecyl phosphate layers strongly suppresses ferromagnetic ordering as a result of surface defect passivation while maintaining bulk-like n-type semiconducting properties, which reveals significance of interfacial states to engineer functional properties of nanosheet-based hybrid materials.

Enhanced and engineered d0 ferromagnetism in molecularly-thin zinc oxide nanosheets

Iron(II) spin crossover complexes with branched long alkyl chain

Iron(III) spin-crossover compounds, [Fe(qnal)2]CF3SO3·MeOH (1·MeOH) and [Fe(qnal)2]CF3SO3·acetone (1·acetone) were prepared and their spin transition properties were characterized by magnetic susceptibility measurement, Mossbauer spectroscopy and single crystal analysis. Two iron(III) compounds exhibited abrupt spin transition with thermal hysteresis loop (T
 1/2↑ = 115 K and T
 1/2↓ = 104 K for 1·MeOH, and T
 1/2↑ = 133 K and T
 1/2↓ = 130 K for 1·acetone). Single crystal analysis revealed both of the structures in high-spin (HS) and low-spin (LS) states for 1·acetone. The difference of bond length between the HS and LS states for 1·acetone was ~0.10 A, which was corresponding to that of typical iron(III) SCO compounds. Specially, it showed strong intermolecular interactions by π–π stacking formed between the neighbor complexes leading to 2-D sheet. Both 1·MeOH and 1·acetone exhibited LIESST effect when it was illuminated at 1000 nm. We also confirmed that the introduction of strong intermolecular interactions, such as π–π stacking, can play an important role in LIESST effect.

Tetsuya Shimizu

Papers

Spin-crossover in cobalt(II) compounds containing terpyridine and its derivatives

Enhanced and engineered d0 ferromagnetism in molecularly-thin zinc oxide nanosheets

Iron(II) spin crossover complexes with branched long alkyl chain

Photo-switchable spin-crossover iron(III) compound based on intermolecular interactions

Spin crossover polymeric iron(II) complex based on triazole with branched long alkyl chain