Transition-metal complexes of O2 and N2 play an important role in the environment, chemical industry, and metalloenzymes. This Perspective compares and contrasts the binding modes, reduction levels, and electronic influences on the nature of the bound O2 or N2 group in these complexes. The charge distribution between the metal and the diatomic ligand is variable, and different models for describing the adducts have evolved. In some cases, single resonance structures (e.g. M–superoxide = M–O2−) are accurate descriptions of the adducts. Recent studies have shown that the magnetic coupling in certain N22− complexes differs between resonance forms, and can be used to distinguish experimentally between resonance structures. On the other hand, many O2 and N2 complexes cannot be described well with a simple valence-bond model. Defining the situations where ambiguities occur is a fertile area for continued study.

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Metal-dioxygen and metal-dinitrogen complexes: where are the electrons?

A simple hydrothermal process is proposed for synthesizing SnO2 quantum dots (QDs), in which hydrazine hydrate is used as the mineralizer instead of NaOH. X-ray diffraction, high-resolution transmission electron microscopy (HRTEM) and UV–vis diffuse reflectance spectroscopy (DRS) were employed to characterize the product. The HRTEM image shows that the diameters of the SnO2 nanoparticles fall into a small range of 2.3–3.1 nm, with the majority being less than the exciton Bohr radius of SnO2 (~2.7 nm). Analysis of the DRS spectrum showed the band gap of the SnO2 QDs to be 3.88 eV, exhibiting a 0.28 eV blue shift from that of the bulk SnO2 (3.6 eV). The mechanism for hydrothermal synthesis of the SnO2 QDs using hydrazine hydrate as the mineralizer is discussed.

https://iopscience.iop.org/article/10.1088/0957-4484/17/9/052/pdf

A simple hydrothermal route for synthesizing SnO2 quantum dots

https://www.tandfonline.com/doi/pdf/10.1088/1468-6996/12/1/013004

Zinc stannate nanostructures: hydrothermal synthesis

Preparation of fine Ni powders from nickel hydrazine complex

In this work, various novel NiO hierarchical nanostructures, including mesoporous nanotubes by nanoparticles self-assembly, nanowire bundles, dandelions, hollow spheres by rods self–assembly, have been fabricated by a simple hydrothermal process and subsequent thermal decomposition at atmosphere. A detailed study of the effect of experimental parameters on the morphology is also presented. Results and analyses demonstrated that oxalic-acid/NaOH molar ratio has an immense function in the subtle morphology control of NiO products. Electrochemical characterization demonstrated that the mesoporous NiO nanotubes were capable of delivering a specific capacitance (SC) of 405 F g−1 at the current density of 0.5 A g−1 and offered good capacitance retention of ca. 91% after 1500 continuous charge-discharge cycles. This soundly indicates that as electrode material, the as-prepared NiO mesoporous nanostructures could meet key requirements in terms of large power density, outstanding rate capability and excellent electrochemical stability.

Mesoporous NiO with various hierarchical nanostructures by quasi-nanotubes/nanowires/nanorods self-assembly: controllable preparation and application in supercapacitors

A. Braibanti

Papers

The nitrogen-nitrogen stretching band in hydrazine derivatives and complexes