Inorganics, Volume 8, Issue 3 (March 2020) – 6 articles

A series of [Re(N^N)(CO)₃(Cl)] (N^N = diimine) complexes based on 4-(pyrid-2-yl)-1,2,3-triazole (1), 1-benzyl-4-(pyrimidin-2-yl)-1,2,3-triazole (2), and 1-benzyl-4-(pyrazin-2-yl)-1,2,3-triazole (3) diimine ligands were prepared and their photophysical and electrochemical properties were characterized. The ligand-based reduction wave is shown to be highly sensitive to the nature of the triazole-based ligand, with the peak potential shifting by up to 600 mV toward more positive potential from 1 to 3. All three complexes are phosphorescent in solution at room temperature with λ_max ranging from 540 nm (1) to 638 nm (3). Interestingly, the complexes appear to show inverted energy-gap law behaviour (τ = 43 ns for 1 versus 92 ns for 3), which is tentatively interpreted as reduced thermal accessibility of metal-centred (³MC) states from photoexcited metal to ligand charge transfer (³MLCT) states upon stabilisation of the N^N-centred lowest unoccupied molecular orbital (LUMO). The photophysical characterisation, supported by computational data, demonstrated a progressive stabilization of the LUMO from complex 1 to 3, which results in a narrowing of the HOMO–LUMO energy gap (HOMO = highest occupied molecular orbital) across the series and, correspondingly, red-shifted electronic absorption and photoluminescence spectra. The two complexes bearing pyridyl (1) and pyrimidyl (2) moieties, respectively, showed a modest ability to catalyse the electroreduction of CO₂, with a peak potential at ca. −2.3 V versus Fc/Fc⁺. The catalytic wave that is observed in the cyclic voltammograms is slightly enhanced by the addition of water as a proton source. Full article

The order of OH groups in the crystal structure of SbC₂O₄OH, a potential precursor in the synthesis of ternary oxides, was debated. Neutron diffraction on the deuteride SbC₂O₄OD revealed disordered OD groups with half occupation for deuterium atoms on either side of a mirror plane (SbC₂O₄OD at T = 298(1) K: Pnma, a = 582.07(3) pm, b = 1128.73(5) pm, c = 631.26(4) pm). O–H stretching frequencies are shifted by a factor of 1.35 from 3390 cm⁻¹ in the hydride to 2513 cm⁻¹ in the deuteride as seen in infrared spectra. SbC₂O₄OH suffers radiation damage in a synchrotron beam, which leaves a dark amorphous residue. Thermal decomposition at 564 K yields antimony oxide, carbon dioxide, carbon oxide, and water in an endothermic reaction. When using SbC₂O₄OH as a precursor in reactions, however, ternary oxides are only formed at much higher temperatures. Full article

This paper reviews synthetic concepts for the functionalization of various inorganic nanoparticles with a shell consisting of organic polymers and possible applications of the resulting hybrid materials. A polymer coating can make inorganic nanoparticles soluble in many solvents as individual particles and not only do low molar mass solvents become suitable, but also polymers as a solid matrix. In the case of shape anisotropic particles (e.g., rods) a spontaneous self-organization (parallel orientation) of the nanoparticles can be achieved, because of the formation of lyotropic liquid crystalline phases. They offer the possibility to orient the shape of anisotropic nanoparticles macroscopically in external electric fields. At least, such hybrid materials allow semiconducting inorganic nanoparticles to be dispersed in functional polymer matrices, like films of semiconducting polymers. Thereby, the inorganic nanoparticles can be electrically connected and addressed by the polymer matrix. This allows LEDs to be prepared with highly fluorescent inorganic nanoparticles (quantum dots) as chromophores. Recent works have aimed to further improve these fascinating light emitting materials. Full article

Here we highlight past work on metal–dithiolene interactions and how the unique electronic structure of the metal–dithiolene unit contributes to both the oxidative and reductive half reactions in pyranopterin molybdenum and tungsten enzymes. The metallodithiolene electronic structures detailed here were interrogated using multiple ground and excited state spectroscopic probes on the enzymes and their small molecule analogs. The spectroscopic results have been interpreted in the context of bonding and spectroscopic calculations, and the pseudo-Jahn–Teller effect. The dithiolene is a unique ligand with respect to its redox active nature, electronic synergy with the pyranopterin component of the molybdenum cofactor, and the ability to undergo chelate ring distortions that control covalency, reduction potential, and reactivity in pyranopterin molybdenum and tungsten enzymes. Full article

The compounds [1,4′-bipyridine]-1,1′-diium [CuCl₄] (1) and [1,4′-bipyridine]-1,1′-diium [CuBr₄] (2) were prepared and their crystal structures and magnetic properties are reported. The compounds are isomorphous and crystallize in the monoclinic space group C2/c. The cation crystallizes in a two-fold disordered fashion with the terminal nitrogen and carbon atoms exhibiting 50% occupancies. This results in a crystal packing arrangement with significant hydrogen bonding that is very similar to that observed in the corresponding 4,4′-bipyridinediium complexes. Temperature dependent magnetic susceptibility measurements and room temperature EPR spectroscopy indicate the presence of very weak antiferromagnetic exchange. The data were fit to the Curie–Weiss law and yielded Weiss constants of −0.26(5) K (1) and −1.0(1) K (2). Full article

Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel, sustainable technologies towards a CO₂-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na⁺, Mg²⁺ and Ca²⁺, while Al³⁺-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials, the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore, it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE, the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed. Full article