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Boron-hydrogen compounds are of increasing importance as electrolytes in solid state batteries, for hydrogen storage and possibly as high temperature super conductors. Solvent based methods are of increasing importance to obtain pure products, for purification of materials and also for the synthesis of novel compounds. In this context, the solubility information of several classes of metal-boron-hydrogen compounds such as borohydrides, closo-decahydridodecaborates, closo-dodecahydridododecaborates, arachno- and nido-hydridoborates in typical solvents is vital. This information is currently dispersed in the literature, hence the need to present a cohesive summary and comparison of these properties. This review collects, analyses and discusses the available data to provide inspiration for the future design of new synthesis routes and the discovery of novel materials. [ABSTRACT FROM AUTHOR]

Mg(B3H8)2 is a crucial reaction intermediate in the thermal decomposition of the hydrogen storage material Mg(BH4)2 and is discussed as a potential solid-state Mg-ion conductor. We successfully synthesized unsolvated Mg(B3H8)2 and highlight that Mg(B3H8)2 exists mainly as a low-dimensional solid. In addition, the Mg2+ conductivity was evaluated to be 1.4.10−4 S cm−1 at 80 °C. [ABSTRACT FROM AUTHOR]

Lithium borohydride is a promising lithium ion conductor for all-solid-state batteries. However, the compound only exhibits high ionic conductivity at elevated temperatures, typically above 110 °C. It was shown that the addition of oxides such as silica or alumina increases the room temperature ionic conductivity by 3 orders of magnitude. The origin of this remarkable effect is not yet well understood. Here, we investigate the influence of oxide surface groups on the ionic conductivity of LiBH4/SiO2 nanocomposites. We systematically varied the density and nature of the surface groups of mesoporous silica by heat treatment at different temperatures, or surface functionalization, and subsequently prepared LiBH4/SiO2 nanocomposites by melt infiltration. The ionic conductivity is strongly influenced by the heat treatment temperature, hence the density of the free surface silanol groups. Replacing some of the silanol groups with hydrophobic surface groups resulted in an order of magnitude reduction of the room temperature ionic conductivity, suggesting that their presence is crucial to obtain high ionic conductivity in the nanocomposites. This systematic study and insight provide a basis for further exploration of the impact of surface groups, and for the rational design of novel solid-state nanocomposite electrolytes via interface engineering. [ABSTRACT FROM AUTHOR]

We report on the identification and survey of the Pb4Ln2O7 series (Ln = La, Gd, Sm and Nd) which turn out to be real van der Waals 2D oxides. In the neutral layers, strong covalent Pb–O bonds together with external stereoactive Pb2+ lone pairs, which act as sensitizers, lead to an ideal matrix for enhanced and tunable luminescence by lanthanide emitters, tested here for Sm3+ and Eu3+ doping. DFT calculations and preliminary ex-solution experiments validate the weak bonding between the layers separated by 3.5 Å and suggest a indirect to direct crossover realized by isolating the layers. [ABSTRACT FROM AUTHOR]

Fluoride substitution in LiBH4 is studied by investigation of LiBH4–LiBF4 mixtures (9 : 1 and 3 : 1). Decomposition was followed by in situ synchrotron radiation X-ray diffraction (in situ SR-PXD), thermogravimetric analysis and differential scanning calorimetry with gas analysis (TGA/DSC-MS) and in situ infrared spectroscopy (in situ FTIR). Upon heating, fluoride substituted LiBH4 forms (LiBH4−xFx) and decomposition occurs, releasing diborane and solid decomposition products. The decomposition temperature is reduced more than fourfold relative to the individual constituents, with decomposition commencing at T = 80 °C. The degree of fluoride substitution is quantified by sequential Rietveld refinement and shows a selective manner of substitution. In situ FTIR experiments reveal formation of bands originating from LiBH4−xFx. Formation of LiF and observation of diborane release implies that the decomposing materials have a composition that facilitates formation of diborane and LiF, i.e. LiBH4−xFx (LiBH3F). An alternative approach for fluoride substitution was performed, by addition of Et3N·3HF to LiBH4, yielding extremely unstable products. Spontaneous decomposition indicates fluoride substitution to have occurred. From our point of view, this is the most significant destabilization effect seen for borohydride materials so far. [ABSTRACT FROM AUTHOR]

Backscattered Raman optical activity (ROA) spectra are measured for Δ- and Λ-tris-(ethylenediamine)rhodium(iii) chloride in aqueous solution. In addition, the spectra of the four possible conformers in the Λ configuration are investigated by ab initio calculations. The Λ(δδδ) conformer is in best agreement with experimental spectra and examined in more details. The two most stable conformers according to the calculations are not compatible with the experimental ROA spectrum. Insights into the origin of observed band intensities are obtained by means of group coupling matrices. The influence of the first solvation shell is explored via an ab initio molecular dynamics simulation. Taking explicit solvent molecules into account further improves the agreement between calculation and experiment. Analysis of selected normal modes using group coupling matrices shows that solvent molecules lead to normal mode rotation and thus contribute to the ROA intensity, whereas the contribution of the Rh can be neglected. [ABSTRACT FROM AUTHOR]

A series of 6 novel triarylamine-containing oxadiazole compounds (o-PCzPOXD, o-ICzPOXD, o-TPATOXD, o-PCzTOXD, o-ICzTOXD, o-CzTOXD) have been designed, synthesized and characterized concerning applications as host materials in PHOLED devices. To further improve the ortho-linkage concept, the impact of incorporating planarized electron-donating triarylamine (TAA) structures on intramolecular charge transfer was examined. The effect was evaluated for two series of electron-accepting oxadiazole scaffolds, realizing ortho-linkage on the benzene (POXD) and the thiophene (TOXD) cores. Thermal analysis shows increased glass-transition temperatures for planarized structures indicating an improved morphological stability. A higher degree of planarization also results in significantly increased singlet and triplet energy values, revealing the impact on the intramolecular charge transfer. Employing the developed materials, red (o-TPATOXD: CEmax: 28.8 cd A−1, EQEmax: 16.9%), green (o-PCzPOXD: CEmax: 62.9 cd A−1, EQEmax: 17.1%) and blue (o-PCzPOXD: CEmax: 29.8 cd A−1, EQEmax: 13.4%) devices were achieved showing remarkably low efficiency roll-off for planarized donors. Hence, this is the first report of efficient blue devices for this specific class of host materials. It is proposed that the results correlate with an increasing ortho-linkage effect and decreasing donor strength of the TAA moiety by planarization and, thus, tackling one of the major challenges in PHOLED research: improving both triplet energy and compound stability. [ABSTRACT FROM AUTHOR]

Correction for 'Experimental investigation of Mg(B3H8)2 dimensionality, materials for energy storage applications' by Romain Moury et al., Dalton Trans., 2020, 49, 12168–12173, https://doi.org/10.1039/D0DT02170A. [ABSTRACT FROM AUTHOR]

Lithium borohydride is a promising lithium ion conductor for all-solid-state batteries. However, the compound only exhibits high ionic conductivity at elevated temperatures, typically above 110 °C. It was shown that the addition of oxides such as silica or alumina increases the room temperature ionic conductivity by 3 orders of magnitude. The origin of this remarkable effect is not yet well understood. Here, we investigate the influence of oxide surface groups on the ionic conductivity of LiBH 4 /SiO 2 nanocomposites. We systematically varied the density and nature of the surface groups of mesoporous silica by heat treatment at different temperatures, or surface functionalization, and subsequently prepared LiBH 4 /SiO 2 nanocomposites by melt infiltration. The ionic conductivity is strongly influenced by the heat treatment temperature, hence the density of the free surface silanol groups. Replacing some of the silanol groups with hydrophobic surface groups resulted in an order of magnitude reduction of the room temperature ionic conductivity, suggesting that their presence is crucial to obtain high ionic conductivity in the nanocomposites. This systematic study and insight provide a basis for further exploration of the impact of surface groups, and for the rational design of novel solid-state nanocomposite electrolytes via interface engineering.

Fluoride substitution in LiBH 4 is studied by investigation of LiBH 4 -LiBF 4 mixtures (9 : 1 and 3 : 1). Decomposition was followed by in situ synchrotron radiation X-ray diffraction (in situ SR-PXD), thermogravimetric analysis and differential scanning calorimetry with gas analysis (TGA/DSC-MS) and in situ infrared spectroscopy (in situ FTIR). Upon heating, fluoride substituted LiBH 4 forms (LiBH 4-x F x ) and decomposition occurs, releasing diborane and solid decomposition products. The decomposition temperature is reduced more than fourfold relative to the individual constituents, with decomposition commencing at T = 80 °C. The degree of fluoride substitution is quantified by sequential Rietveld refinement and shows a selective manner of substitution. In situ FTIR experiments reveal formation of bands originating from LiBH 4-x F x . Formation of LiF and observation of diborane release implies that the decomposing materials have a composition that facilitates formation of diborane and LiF, i.e. LiBH 4-x F x (LiBH 3 F). An alternative approach for fluoride substitution was performed, by addition of Et 3 N·3HF to LiBH 4 , yielding extremely unstable products. Spontaneous decomposition indicates fluoride substitution to have occurred. From our point of view, this is the most significant destabilization effect seen for borohydride materials so far.

Backscattered Raman optical activity (ROA) spectra are measured for Δ- and Λ-tris-(ethylenediamine)rhodium(III) chloride in aqueous solution. In addition, the spectra of the four possible conformers in the Λ configuration are investigated by ab initio calculations. The Λ(δδδ) conformer is in best agreement with experimental spectra and examined in more details. The two most stable conformers according to the calculations are not compatible with the experimental ROA spectrum. Insights into the origin of observed band intensities are obtained by means of group coupling matrices. The influence of the first solvation shell is explored via an ab initio molecular dynamics simulation. Taking explicit solvent molecules into account further improves the agreement between calculation and experiment. Analysis of selected normal modes using group coupling matrices shows that solvent molecules lead to normal mode rotation and thus contribute to the ROA intensity, whereas the contribution of the Rh can be neglected.

Inorganic borohydrides are actively studied in view of potential hydrogen storage applications. These compounds can be obtained by a variety of reactions ranging from high temperature reactions of the elements to exchange reactions in solution or in solid state. Different approaches will be discussed and compared.