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The structural variability of a compound class is an important criterion for the research into phosphor host lattices for phosphor-converted light-emitting diodes (pc-LEDs). Especially, nitridophosphates and the related class of imidonitridophosphates are promising candidates. Recently, the ammonothermal approach has opened a systematic access to this substance class with larger sample quantities. We present the successful ammonothermal synthesis of the imidonitridophosphate Ba 4 P 4 N 8 (NH) 2 :Eu 2+ . Its crystal structure is solved by X-ray diffraction and it crystallizes in space group Cc (no. 9) with lattice parameters a=12.5250(3), b=12.5566(4), c=7.3882(2) Å and β=102.9793(10)°. For the first time, adamantane-type (imido)nitridophosphate anions [P 4 N 8 (NH) 2 ] 8- are observed next to metal ions other than alkali metals in a compound. The presence of imide groups in the structure and the identification of preferred positions for the hydrogen atoms are performed using a combination of quantum chemical calculations, Fourier-transform infrared, and solid-state NMR spectroscopy. Eu 2+ doped samples exhibit cyan emission (λ max =498 nm, fwhm=50 nm/1981 cm -1 ) when excited with ultraviolet light with an impressive internal quantum efficiency (IQE) of 41 %, which represents the first benchmark for imidonitridophosphates and is promising for potential industrial application of this compound class., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Nitridophosphates are subject of current research, as they have a broad spectrum of properties and potential applications, such as ion conductors or luminescent materials. Yet, the subclass of imidonitridophosphates has been studied less extensively. The primary reason is that the controlled N-H functionalization of nitridophosphates is not straight forward, making targeted synthesis more challenging. Inspired by the high-pressure (HP) post-synthetic modification of nitridophosphates, we present the topochemical HP deprotonation of phosphorus nitride imides using the high-pressure polymorph β-PN(NH) as an example. Additional incorporation of Zn 2+ results in the first quaternary transition metal imidonitridophosphate ZnH 2 P 4 N 8 . The crystal structure was elucidated by single-crystal X-ray diffraction (SCXRD), energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD) and solid-state magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). In addition, the presence of H as part of an imide group was confirmed by IR spectroscopy. The potential of this defunctionalization approach for controlling the N-H content is demonstrated by the preparation of partially deprotonated intermediates Zn x H 4-2x P 4 N 8 (x≈0.5, 0.85). This topochemical high-pressure reaction represents a promising way to prepare, control and manipulate new imide-based materials without altering their overall anionic framework., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Oxide zeolites are synthesized from aqueous solutions in an established way employing hydrothermal synthesis. Transferring this approach to nitride zeolites requires a solvent providing nitrogen for which ammonia has proven to be particularly suitable. We present the successful ammonothermal synthesis of the (oxo)nitridosilicate compounds Ce 3 [Si 6 N 11 ], Li 2 RE 4 [Si 4 N 8 ]O 3 (RE=La, Ce) and K 1.25 Ce 7.75 [Si 11 N 21 O 2 ]O 0.75 . Within this procedure, the usage of supercritical ammonia as a solvent as well as the utilization of the mineralizers NaN 3 , Li 3 N and KN 3 , respectively, allowed the targeted synthesis of large single crystals. Formation of these (oxo)nitridosilicates depends mainly on the employed mineralizer despite their similar degree of condensation. The three compounds were structurally characterized using X-ray diffraction and their crystal structures contain a wide range of different ring sizes within their tetrahedra networks. The zeolite(-like) crystal structures are elucidated and compared to known nitridosilicate representatives of the respective structure types. Their elemental composition was investigated using energy-dispersive X-ray (EDX) spectroscopy and incorporation of the O rather than N-H functionality was confirmed by Fourier-Transform infrared (FTIR) spectroscopy as well as by charge distribution (CHARDI) and bond valence sum (BVS) calculations. The presented examples demonstrate that ammonothermal synthesis provides a one-step access from elemental starting materials towards nitride zeolites., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Based on their various and outstanding properties, binary nitrides are used as (synthesis) materials in industry and research. Hence, their comprehensive characterization by analytical methods is of particular interest. Since Nuclear Magnetic Resonance (NMR) spectroscopy is very sensitive to the symmetry of the electronic density distribution, it is a suitable tool for the investigation of rock-salt structure types and, especially, for those with known stoichiometry issues. Here, we report on magic-angle spinning NMR spectra of the nuclides 89 Y (I=12), 139 La (I=72) and 14 N (I=1) in polycrystalline samples of YN, LaN and LuN. Due to the high symmetry of their crystal structures, the spectra of all nuclides do not exhibit anisotropic effects of significant magnitude. The resulting isotropic chemical shift values are δiso( 89 Y) = 516 ppm for YN, δiso( 139 La) =1294 ppm for LaN, and δiso( 14 N) = 457 ppm (YN), 788 ppm (LaN) and 384 ppm (LuN). The newly determined δiso( 14 N) values for these three binary nitrides fit well into the previously reported linear correlation between nitrogen distance to the nearest cation and isotropic chemical shift, leading to a better correlation coefficient and reduced error margins for the fit parameters.

Nitridophosphates have emerged as promising host compounds in the field of solid-state lighting. Their industrial relevance has increased significantly, mainly due to recent advances in synthetic approaches under medium-pressure (MP) conditions, including ammonothermal synthesis and hot isostatic pressing (HIP). In this study, we report on the synthesis and characterization of the quaternary representatives Ca x Li 10-2x P 4 N 10 (x=2, 2.7, 4) and Sr 3 Li 4 P 4 N 10 , prepared via a simplified ion exchange reaction under MP conditions, starting from the nitridophosphate-based lithium ion conductor Li 10 P 4 N 10 . The synthesis route allowed for the preservation of the anionic [P 4 N 10 ] 10- structural motif of the starting material, while simultaneously introducing potential doping sites for Eu 2+ by incorporating divalent alkaline earth cations (Ca 2+ /Sr 2+ ). Upon excitation of Eu 2+ doped samples with blue light, strong luminescence due to parity-allowed 4f 6 ( 7 F)5d 1 →4f 7 ( 8 S 7/2 ) transition can be observed in the red (Ca 2 Li 6 P 4 N 10  : Eu 2+ : λ max =626 nm), yellow/orange (Ca 2.7 Li 4.6 P 4 N 10  : Eu 2+ : λ max1 =506 nm, λ max2 =592 nm and Sr 3 Li 4 P 4 N 10  : Eu 2+ : λ max =596 nm) and green (Ca 4 Li 2 P 4 N 10  : Eu 2+ : λ max =546 nm) spectral regions of the visible light. The compounds presented, together with the simplified synthetic approach, demonstrate the significant potential of ion exchange on Li ion conductors for the development of novel nitridophosphates in the future., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Nitrides represent a promising class of materials for a variety of applications. However, bulk synthesis remains a challenging task due to the stability of the N 2 molecule. In this study, we introduce a simple and scalable approach for synthesizing nitride bulk materials. Moderate reaction temperatures are achieved by using reactive starting materials, slow and continuous mixing of the starting materials, and by dissipating heat generated during the reaction. The impact on the synthesis of using different starting materials as nitrogen source and the influence of a flux were examined. γ-Sn 3 N 4 was selected as the model compound. The synthesis of pure γ-Sn 3 N 4 bulk material on a large scale has still been a challenge, although a few synthesis methods were already described in the literature. Here we synthesized γ-Sn 3 N 4 by metathesis reaction of argon-diluted SnCl 4 with Li 3 N, Mg 3 N 2 or Ca 3 N 2 as nitrogen sources. Products were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, dynamic flash combustion analysis, hot gas extraction analysis, X-ray photoelectron spectroscopy, Mössbauer spectroscopy and X-ray absorption and emission spectroscopy. Additionally, single-crystal diffraction data of γ-Sn₃N₄, previously unavailable, were successfully collected., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Compounds of transition metals and beryllium have a wide range of applications, from everyday tools to high tech applications. Remarkably, no single ternary beryllium nitride with a transition metal is known. Here, we report on the synthesis and properties of the first transition metal nitridoberyllates, namely W 2 Be 4 N 5 and W 4 Be 8 N 9 . Both compounds were synthesized in a high-temperature high-pressure approach from Be 3 N 2 and W, using azide generated N 2 as an oxidizing agent. The crystal structures, consisting of alternating layers of WN 6 trigonal prisms and BeN 4 tetrahedra, were elucidated by single-crystal X-ray diffraction (sc-XRD). The separating nitridoberyllate layers show either ambient temperature (α-Be 3 N 2 type) or high temperature (β-Be 3 N 2 type) motifs. W 2 Be 4 N 5 was further corroborated by infrared (IR), nuclear magnetic resonance (NMR) and UV/Vis spectroscopy and vibrating sample magnetometry (VSM) measurements. The latter revealed a mixed valence with an intermediate oxidation state of 3.5 for the W atoms. Both, the synthesis of the first transition metal nitridoberyllates and the synthesis approach using elemental W pave the way to a new field of nitride chemistry., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We report on the synthesis, crystal, and electronic structure, as well as the magnetic, and electric properties of the phosphorus-containing tantalum nitride P 1-x Ta 8+x N 13 (x=0.1-0.15). A high-pressure high-temperature reaction (8 GPa, 1400 °C) of Ta 3 N 5 and P 3 N 5 with NH 4 F as a mineralizing agent yields the compound in the form of black, rod-shaped crystals. Single-crystal X-ray structure elucidation (space group C2/m (no. 12), a=16.202(3), b=2.9155(4), c=11.089(2) Å, β=126.698(7)°, Z=2) shows a network of face- and edge-sharing Ta-centered polyhedra that contains small vacant channels and PN 6 octahedra strands. Atomic resolution transmission electron microscopy reveals an unusual P/Ta disorder. Mixed-valent tantalum atoms exhibit interatomic distances similar to those in metallic tantalum, however, the electrical resistivity is quite high in the order of 10 1  Ω cm. The density of states and the electron localization function indicate localized electrons in both covalent and ionic bonds between P/Ta and N atoms, combined with less localized electrons that do not contribute to interatomic bonds., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The research for wurtzite-type ternary nitride semiconductors containing earth abundant elements with a stoichiometry of 1 : 1 : 2 was focused on metals like Mg or Zn, so far. The vast majority of these Grimm-Sommerfeld analogue compounds crystallize in the β-NaFeO 2 structure, although a second arrangement in space group Pmc2 1 is predicted to be a viable alternative. Despite extensive theoretical and experimental studies, this structure has so far remained undiscovered. Herein, we report on BeGeN 2 in a Pmc2 1 structure, synthesized from Be 3 N 2 and Ge 3 N 4 using a high-pressure high-temperature approach at 6 GPa and 800 °C. The compound was characterized by powder X-ray diffraction (PXRD), solid state nuclear magnetic resonance (NMR), Raman and energy dispersive X-ray (EDX) spectroscopy, temperature-dependent PXRD, second harmonic generation (SHG) and UV/Vis measurements and in addition also compared to its lighter homologue BeSiN 2 in all mentioned analytic techniques. The synthesis and investigation of both the first beryllium germanium nitride and the first ternary wurtzite-type nitride crystallizing in space group Pmc2 1 open the door to a new field of research on wurtzite-type related structures., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Nitridophosphates are in the focus of current research interest due to their structural versatility and properties, such as ion conductivity, ultra-incompressibility and luminescent properties when doped with suitable activator ions. Multinary representatives often require thorough investigation due to the competition with the thermodynamically more stable binary and ternary compounds. Another point of concern is the synthetic control of structural details, which is usually limited by conventional bottom-up syntheses. In this study, we report on the synthesis and characterization of the quaternary nitridophosphate CaLi 2 PN 3 . Various synthesis protocols were used for the preparation of CaLi 2 PN 3 , including the novel nitridophosphate double salt approach. The crystal structure was solved and refined from single-crystal X-ray diffraction data and confirmed by Rietveld refinement, solid-state NMR spectroscopy, EDX measurements and low-cost crystallographic calculations. The experimental results were corroborated by DFT calculations, which revealed the electronic band structure. Formation energy calculations allowed conclusions to be drawn about the stability in comparison to the initial ternary nitridophosphates. The synthesis of CaLi 2 PN 3 exemplifies the enormous potential of medium-pressure syntheses in the field of nitridophosphate research. Furthermore, the presented new synthesis route allows a certain degree of structural control, which is a promising addition to previous synthesis strategies in nitridophosphate chemistry., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Nitridophosphates, with their primary structural motif of isolated or condensed PN 4 tetrahedra, meet many requirements for high performance materials. Their properties are associated with their structural diversity, which is mainly limited by this specific building block. Herein, we present the alkaline earth metal nitridophosphate oxide Ba 3 [PN 3 ]O featuring a trigonal planar [PN 3 ] 4- anion. Ba 3 [PN 3 ]O was obtained using a hot isostatic press by medium-pressure high-temperature synthesis (MP/HT) at 200 MPa and 880 °C. The crystal structure was solved and refined from single-crystal X-ray diffraction data in space group R 3 ‾ ${\bar 3}$ c (no. 167) and confirmed by SEM-EDX, magic angle spinning (MAS) NMR, vibrational spectroscopy (Raman, IR) and low-cost crystallographic calculations (LCC). MP/HT synthesis reveals great potential by extending the structural chemistry of P to include trigonal planar [PN 3 ] 4- motifs., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Ammeline is a simple, readily available, molecular compound, which has been known for nearly 200 years. Despite that, no proper structural characterization of ammeline has been conducted so far. For this reason, the prevalent tautomeric form of ammeline in the solid remained unknown to this date. In the course of this study, its crystal structure was finally established by single-crystal X-ray diffraction. In this structure, ammeline is exclusively found as its 4,6-diamino-1,3,5-triazin-2(1H)-one tautomer and adopts layered structure with an exceptionally high hydrogen bond density. Ammeline shows an interesting amphoteric behavior. Therefore, the synthesis and structural characterization of some of its salts were carried out to investigate the influence of the protonation degree on its molecular structure. In particular, the crystal structure of silver ammelinate monohydrate was solved as the first reported structure containing deprotonated ammeline. Moreover, the crystal structures of three different modifications of ammelinium perchlorate were elucidated and the transformation conditions between them were studied. Lastly, the crystal structure of ammelinediium diperchlorate monohydrate, containing unprecedented doubly protonated ammeline, was determined. The products' thermal behavior was studied by differential thermal analysis and thermogravimetric analysis. The perchlorate salts were additionally examined for their potential as insensitive high-energy-density materials., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Sn 3 P 8 N 16 combines the structural versatility of nitridophosphates and Sn within one compound. It was synthesized as dark gray powder in a high-pressure high-temperature reaction at 800 °C and 6 GPa from Sn 3 N 4 and P 3 N 5 . The crystal structure was elucidated from single-crystal diffraction data (space group C2/m (no. 12), a=12.9664(4), b=10.7886(4), c=4.8238(2) Å, β=109.624(1)°) and shows a 3D-network of PN 4 tetrahedra, incorporating Sn in oxidation states +II and +IV. The Sn cations are located within eight-membered rings of vertex-sharing PN 4 tetrahedra, stacked along the [001] direction. A combination of solid-state nuclear magnetic resonance spectroscopy, 119 Sn Mössbauer spectroscopy and density functional theory calculations was used to confirm the mixed oxidation of Sn. Temperature-dependent powder X-ray diffraction measurements reveal a low thermal expansion of 3.6 ppm/K up to 750 °C, beyond which Sn 3 P 8 N 16 starts to decompose., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Although beryllium and its compounds show outstanding properties, owing to its toxic potential and extreme reaction conditions the chemistry of Be under high-pressure conditions has only been investigated sparsely. Herein, we report on the highly condensed wurtzite-type Be 2 PN 3 , which was synthesized from Be 3 N 2 and P 3 N 5 in a high-pressure high-temperature approach at 9 GPa and 1500 °C. It is the missing member in the row of formula type M 2 PN 3 (M = Mg, Zn). The structure was elucidated by powder X-ray diffraction (PXRD), revealing that Be 2 PN 3 is a double nitride, rather than a nitridophosphate. The structural model was further corroborated by 9 Be and 31 P solid-state nuclear magnetic resonance (NMR) spectroscopy. We present 9 Be NMR data for tetrahedral nitride coordination for the first time. Infrared and energy-dispersive X-ray spectroscopy (FTIR and EDX), as well as temperature dependent PXRD complement the analytical characterization. Density functional theory (DFT) calculations reveal super-incompressible behavior and the remarkable hardness of this low-density material. The formation of Be 2 PN 3 through a high-pressure high-temperature approach expands the synthetic access to Be-containing compounds and may open access to various multinary beryllium nitrides., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The imidonitridosilicate Rb 3 Si 6 N 5 (NH) 6 , being only the second representative of this compound class, was synthesized ammonothermally at 870 K and 230 MPa. Its crystal structure was solved from single-crystal X-ray diffraction data. The imidonitridosilicate crystallizes isotypically with the respective potassium compound in space group P4 1 32 with the lattice parameter a=10.9422(4) Å forming a three-dimensional imidonitridosilicate tetrahedra network with voids for the rubidium ions. The structure model and the presence of the imide groups were verified by Fourier-Transform infrared (FTIR) and magic-angle spinning (MAS) NMR spectroscopy, using cross polarization 15 N{ 1 H} and 29 Si{ 1 H} MAS NMR experiments. Rb 3 Si 6 N 5 (NH) 6 represents a possible intermediate during the ammonothermal synthesis of nitridosilicates. The characterization of such intermediates improves the understanding of the reaction pathway from ammonothermal solutions to nitrides. Thus, the ammonothermal synthesis is an alternative approach to the well-established high-temperature synthesis leading to the compound class of nitridosilicates., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Tetrahedron-based nitrides offer a wide range of properties and applications. Highly condensed nitridophosphates are examples of nitrides that exhibit fascinating luminescence properties when doped with Eu 2+ , making them appealing for industrial applications. Here, we present the first nitridomagnesophosphate solid solution series Ba 3-x Sr x [Mg 2 P 10 N 20 ] : Eu 2+ (x=0-3), synthesized by a high-pressure high-temperature approach using the multianvil technique (3 GPa, 1400 °C). Starting from the binary nitrides P 3 N 5 and Mg 3 N 2 and the respective alkaline earth azides, we incorporate Mg into the P/N framework to increase the degree of condensation κ to 0.6, the highest observed value for alkaline earth nitridophosphates. The crystal structure was elucidated by single-crystal X-ray diffraction, powder X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), and solid-state NMR. DFT calculations were performed on the title compounds and other related highly condensed nitridophosphates to investigate the influence of Mg in the P/N network. Eu 2+ -doped samples of the solid solution series show a tunable narrow-band emission from cyan to green (492-515 nm), which is attributed to the preferred doping of a single crystallographic site. Experimental confirmation of this assumption was provided by overdoping experiments and STEM-HAADF studies on the series as well on the stoichiometric compound Ba 2 Eu[Mg 2 P 10 N 20 ] with additional atomic resolution energy-dispersive X-ray spectroscopy (EDX) mapping., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A series of isostructural imidonitridophosphates AE 2 AlP 8 N 15 (NH) (AE=Ca, Sr, Ba) was synthesized at high-pressure/high-temperature conditions (1400 °C and 5-9 GPa) from alkaline-earth metal nitrides or azides Ca 3 N 2 /Sr(N 3 ) 2 /Ba(N 3 ) 2 and the binary nitrides AlN and P 3 N 5 . NH 4 F served as a hydrogen source and mineralizing agent. The crystal structures were determined by single-crystal X-ray diffraction and feature a three-dimensional network of vertex-sharing PN 4 -tetrahedra forming diverse-sized rings that are occupied by aluminum and alkaline earth ions. These structures represent another example of nitridophosphate-based networks that simultaneously incorporate AlN 6 -octahedra and alkaline-earth-centered polyhedra, with aluminum not participating in the tetrahedra network. They differ from previously reported ones by incorporating non-condensed octahedra instead of strongly condensed octahedra units and contribute to the diversity of multicationic nitridophosphate network structures. The results are supported by atomic resolution EDX mapping, solid-state NMR and FTIR measurements. Eu 2+ -doped samples show strong luminescence with narrow emissions in the range of green to blue under UV excitation, marking another instance of Eu 2+ -luminescence within imidonitridophosphates., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Nitridophosphates and nitridogermanates attract high interest in current research due to their structural versatility. Herein, the elastic properties of GeP 2 N 4 were investigated by single-crystal X-ray diffraction (XRD) upon compression to 44.4(1) GPa in a diamond anvil cell. Its isothermal bulk modulus was determined to be 82(6) GPa. At 44.4(1) GPa, laser heating resulted in the formation of multiple crystalline phases, one of which was identified as unprecedented germanium nitridophosphate GePN 3 . Its structure was elucidated from single-crystal XRD data ( C 2/ c (no. 15), a = 8.666(5), b = 8.076(4), c = 4.691(2) Å, β = 101.00(7)°) and is built up from layers of GeN 6 octahedra and PN 4 tetrahedra. The GeN 6 octahedra form double zigzag chains, while the PN 4 tetrahedra are found in single zigzag chains. GePN 3 can be recovered to ambient conditions with a unit cell volume increase of about 12%. It combines P V and Ge IV in a condensed nitridic network for the first time.

This study presents the synthesis and characterization of oxonitridosilicate phosphates Sr 3 SiP 3 O 2 N 7 , Sr 5 Si 2 P 4 ON 12 , and Sr 16 Si 9 P 9 O 7 N 33 as the first of their kind. These compounds were synthesized under high-temperature (1400 °C) and high-pressure (3 GPa) conditions. A unique structural feature is their common fundamental building unit, a vierer single chain of (Si, P)(O, N) 4 tetrahedra. All tetrahedra comprise substitutional disorder which is why we refer to it as the fundamental disorder unit (FDU). We classified four different FDU motifs, revealing systematic bonding patterns. Including literature known Sr 5 Si 2 P 6 N 16 , three of the four patterns were found in the presented compounds. Common techniques like single-crystal X-ray diffraction (SCXRD), elemental analyses, and 31 P nuclear magnetic resonance (NMR) spectroscopy were utilized for structural analysis. Additionally, low-cost crystallographic calculations (LCC) provided insights into the structure of Sr 16 Si 9 P 9 O 7 N 33 where NMR data were unavailable due to the lack of bulk samples. The optical properties of these compounds, when doped with Eu 2+ , were investigated using photoluminescence excitation (PLE), photoluminescence (PL) measurements, and density functional theory (DFT) calculations. Factors influencing the emission properties, including thermal quenching mechanisms, were discussed. This research reveals the new class of oxonitridosilicate phosphates with unique systematic structural features that offer potential for theoretical studies of luminescence and band gap tuning in insulators., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The first nitridic analog of an amphibole mineral, the quaternary nitridosilicate phosphate Cr 5.7 Si 2.3 P 8 N 24 was synthesized under high-pressure high-temperature conditions at 1400 °C and 12 GPa from the binary nitrides Cr 2 N, Si 3 N 4 and P 3 N 5 , using NH 4 N 3 and NH 4 F as additional nitrogen source and mineralizing agent, respectively. The crystal structure was elucidated by single-crystal X-ray diffraction with microfocused synchrotron radiation (C2/m, a=9.6002(19), b=17.107(3), c=4.8530(10) Å, β=109.65(3)°). The elemental composition was analyzed by energy dispersive X-ray spectroscopy. The structure consists of vertex-sharing PN 4 -tetrahedra forming zweier double chains and edge-sharing (Si,Cr)-centered octahedra forming separated ribbons. Atomic resolution scanning transmission electron microscopy shows ordered Si and Cr sites next to a disordered Si/Cr site. Optical spectroscopy indicates a band gap of 2.1 eV. Susceptibility measurements show paramagnetic behavior and support the oxidation state Cr +IV , which is confirmed by EPR. The comprehensive analysis expands the field of Cr-N chemistry and provides access to a nitride analog of one of the most prevalent silicate structures., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We report on the synthesis of two-layered alkali germanates, Na 2 Ge 4 O 7 and K 2 Ge 4 O 7 . Both compounds were synthesized by using the ammonothermal method at 823 K and 100 MPa. Under these conditions, germanium is partially reduced from the +IV state to +II, forming mixed-valence compounds with the rarely observed [Ge (II) O 3 ] 4- unit. The valence state was verified by X-ray photoelectron spectroscopy (XPS) and was accompanied by theoretical calculations alongside vibrational spectroscopy and single-crystal X-ray structure determination. The compounds crystallize in the trigonal space groups (Na 2 Ge 4 O 7 : P 3̅ c 1 and K 2 Ge 4 O 7 : P 3̅ m 1) and feature layers of corner sharing [Ge (II) O 3 ] 4- and [Ge (IV) 2 O 7 ] 6- units forming [Ge (II) 2 Ge (IV) 2 O 7 ] 2- polyanions. These layers are separated by alkali metal ions. The compounds are colorless insulators with band gaps of 4.0-4.2 eV. According to the Robin-Day classification, both compounds can be described as class I materials, where the valences are trapped on specific sites.

High-pressure, high-temperature (HP/HT) syntheses are essential for modern high-performance materials. Phosphorus nitride, nitridophosphate, and more generally nitride syntheses benefit greatly from HP/HT conditions. In this contribution, we present the first systematic in situ investigation of a nitridophosphate HP/HT synthesis using the reaction of zinc nitride Zn 3 N 2 and phosphorus(V) nitride P 3 N 5 to the nitride semiconductor Zn 2 PN 3 as a case study. At a pressure of 8 GPa and temperatures up to 1300 °C, the reaction was monitored by energy-dispersive powder X-ray diffraction (ED-PXRD) in a large-volume press at beamline P61B at DESY. The experiments investigate the general behavior of the starting materials under extreme conditions and give insight into the reaction. During cold compression and subsequent heating, the starting materials remain crystalline above their ambient-pressure decomposition points, until a sufficient minimum temperature is reached and the reaction starts. The reaction proceeds via ion diffusion at grain boundaries with an exponential decay in the reaction rate. Raising the temperature above the minimum required value quickly completes the reaction and initiates single-crystal growth. After cooling and decompression, which did not influence the resulting product, the recovered sample was analyzed by energy-dispersive X-ray (EDX) spectroscopy.

We have previously presented a computational protocol that is based on an embedded cluster model and operates in the framework of TD-DFT in conjunction with the excited state dynamics (ESD) approach. The protocol is able to predict the experimental absorption and emission spectral shapes of Eu 2+ -doped phosphors. In this work, the applicability domain of the above protocol is expanded to Eu 2+ -doped phosphors bearing multiple candidate Eu doping centers. It will be demonstrated that this protocol provides full control of the parameter space that describes the emission process. The stability of Eu doping at various centers is explored through local energy decomposition (LED) analysis of DLPNO-CCSD(T) energies. This enables further development of the understanding of the electronic structure of the targeted phosphors, the diverse interactions between Eu and the local environment, and their impact on Eu doping probability, and control of the emission properties. Hence, it can be employed to systematically improve deficiencies of existing phosphor materials, defined by the presence of various intensity emission bands at undesired frequencies, towards classes of candidate Eu 2+ -doped phosphors with desired narrow band red emission. For this purpose, the chosen study set consists of three UCr 4 C 4 -based narrow-band phosphors, namely the known alkali lithosilicates RbNa[Li 3 SiO 4 ] 2 :Eu 2+ (RNLSO2), RbNa 3 [Li 3 SiO 4 ] 4 :Eu 2+ (RNLSO) and their isotypic nitridolithoaluminate phosphors consisting of CaBa[LiAl 3 N 4 ] 2 :Eu 2+ (CBLA2) and the proposed Ca 3 Ba[LiAl 3 N 4 ] 4 :Eu 2+ (CBLA), respectively. The theoretical analysis presented in this work led us to propose a modification of the CBLA2 phosphor that should have improved and unprecedented narrow band red emission properties. Finally, we believe that the analysis presented here is important for the future rational design of novel Eu 2+ -doped phosphor materials, with a wide range of applications in science and technology.

The elements hydrogen, carbon, and nitrogen are among the most abundant in the solar system. Still, little is known about the ternary compounds these elements can form under the high-pressure and high-temperature conditions found in the outer planets' interiors. These materials are also of significant research interest since they are predicted to feature many desirable properties such as high thermal conductivity and hardness due to strong covalent bonding networks. In this study, the high-pressure high-temperature reaction behavior of malononitrile H 2 C(CN) 2 , dicyandiamide (H 2 N) 2 C=NCN, and melamine (C 3 N 3 )(NH 2 ) 3 was investigated in laser-heated diamond anvil cells. Two previously unknown compounds, namely α-C(NH) 2 and β-C(NH) 2 , have been synthesized and found to have fully sp 3 -hybridized carbon atoms. α-C(NH) 2 crystallizes in a distorted β-cristobalite structure, while β-C(NH) 2 is built from previously unknown imide-bridged 2,4,6,8,9,10-hexaazaadamantane units, which form two independent interpenetrating diamond-like networks. Their stability domains and compressibility were studied, for which supporting density functional theory calculations were performed., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Skutterudites are of high interest in current research due to their diversity of structures comprising empty, partially filled and filled variants, mostly based on metallic compounds. We herein present Ba 12 [BN 2 ] 6.67 H 4 , forming a non-metallic filled anti-skutterudite. It is accessed in a solid-state ampoule reaction from barium subnitride, boron nitride and barium hydride at 750 °C. Single-crystal X-ray and neutron powder diffraction data allowed to elucidate the structure in the cubic space group Im 3 ‾ ${\bar{3}}$ (no. 204). The barium and hydride atoms form a three-dimensional network consisting of corner-sharing HBa 6 octahedra and Ba 12 icosahedra. Slightly bent [BN 2 ] 3- units are located in the icosahedra and the voids in-between. 1 H and 11 B magic angle spinning (MAS) NMR experiments and vibrational spectroscopy further support the structure model. Quantum chemical calculations coincide well with experimental results and provide information about the electronic structure of Ba 12 [BN 2 ] 6.67 H 4 ., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

In this work, we present the synthesis, characterization, and optical properties of Sr 5 Si 7 P 2 N 16 :Eu 2+ , the first tetrahedral (Si,P)-N network in which Si occupies more than 50% of the tetrahedra. While past studies have shown progress with anionic (Si,P)-N networks, the potential of silicon-rich compounds remains untapped. The synthesized compound Sr 5 Si 7 P 2 N 16 exhibits a unique mixture of substitutional order and positional disorder within its network. The analytical challenges posed by the similarities between Si 4+ and P 5+ , along with the network's disorder, were overcome by combining single-crystal X-ray diffraction and scanning transmission electron microscopy EDX mapping. Low-cost crystallographic calculations provided additional insights into the identification of tetrahedral occupations in mixed networks. Luminescence investigations on Sr 5 Si 7 P 2 N 16 :Eu 2+ revealed yellow emission, adding to the known blue, green, and orange emission maxima of Sr-(Si,P)-N networks, highlighting the variability of such compounds.

Alkali nitridophosphates AP 4 N 7 and A 3 P 6 N 11 (A=Na, K, Rb, Cs) have been known for decades. However, their Li homologues have remained elusive. In this work, the highly condensed lithium (imido)nitridophosphates LiP 4 N 7 and Li 3-x P 6 N 11-x (NH) x (x=1.66(3)) were synthesized from LiPN 2 and P 3 N 5 in the multianvil press at 10 GPa. They constitute the first lithium nitridophosphates with 3D networks exhibiting a degree of condensation larger than 0.5 and high thermal stability. LiP 4 N 7 crystallizes in the orthorhombic space group P2 1 2 1 2 1 with a=4.5846(6) Å, b=8.0094(11) Å, and c=13.252(2) Å (Z=4). Li 3-x P 6 N 11-x (NH) x crystallizes in the triclinic space group P 1 - ${\mathrel{\mathop{{\rm { 1}}}\limits^{{\rm -}}}}$ with Z=2, a=4.6911(11) Å, b=7.024(2) Å, c=12.736(3) Å, α=87.726(11), β=80.279(11), and γ=70.551(12)°. Both compounds are stable against hydrolysis in air., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Carbon nitrides featuring three-dimensional frameworks of CN 4 tetrahedra are one of the great aspirations of materials science, expected to have a hardness greater than or comparable to diamond. After more than three decades of efforts to synthesize them, no unambiguous evidence of their existence has been delivered. Here, the high-pressure high-temperature synthesis of three carbon-nitrogen compounds, tI14-C 3 N 4 , hP126-C 3 N 4 , and tI24-CN 2 , in laser-heated diamond anvil cells, is reported. Their structures are solved and refined using synchrotron single-crystal X-ray diffraction. Physical properties investigations show that these strongly covalently bonded materials, ultra-incompressible and superhard, also possess high energy density, piezoelectric, and photoluminescence properties. The novel carbon nitrides are unique among high-pressure materials, as being produced above 100 GPa they are recoverable in air at ambient conditions., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Multianionic metal hydrides, which exhibit a wide variety of physical properties and complex structures, have recently attracted growing interest. Here we present Sr 6 N[BN 2 ] 2 H 3 , prepared in a solid-state ampoule reaction at 800 °C, as the first combination of nitridoborate, nitride and hydride anions within a single compound. The crystal structure was solved from single-crystal X-ray and neutron powder diffraction data in space group P2 1 /c (no. 14), revealing a three-dimensional network of undulated layers of nitridoborate units, strontium atoms and hydride together with nitride anions. Magic angle spinning (MAS) NMR and vibrational spectroscopy in combination with quantum chemical calculations further confirm the structure model. Electrochemical measurements suggest the existence of hydride ion conductivity, allowing the hydrides to migrate along the layers., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The crystalline lithium oxonitridophosphate Li 8+x P 3 O 10-x N 1+x , was obtained in an ampoule synthesis from P 3 N 5 and Li 2 O. The compound crystallizes in the triclinic space group P 1 - ${\mathrel{\mathop{{\rm { 1}}}\limits^{{\rm -}}}}$ with a=5.125(2), b=9.888(5), c=10.217(5) Å, α=70.30(2), β=76.65(2), γ=77.89(2)°. Li 8+x P 3 O 10-x N 1+x is a double salt, the structure of which contains distinctive complex anion species, namely non-condensed P(O,N) 4 tetrahedra, and P(O,N) 7 double tetrahedra connected by one N atom. Additionally, there is mixed occupation of O/N positions, which enables further anionic species by variation of O/N occupancies. To characterize these motifs in detail, complementary analytical methods were applied. The double tetrahedron exhibits significant disorder in single-crystal X-ray diffraction. Furthermore, the title compound is a Li + ion conductor with a total ionic conductivity of 1.2×10 -7  S cm -1 at 25 °C, and a corresponding total activation energy of 0.47(2) eV., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Tetrahedra-based nitridophosphates show a rich structural chemistry, which can be further extended by incorporating cations in higher coordinated positions, for example, in octahedral voids or by substituting the nitrogen atoms in the network with other anions. Following this approach, SrAl 5 P 4 N 10 O 2 F 3 was synthesized at high-temperature and high-pressure conditions using a multianvil press (1400 °C, 5 GPa) starting from Sr(N 3 ) 2 , c-PON, P 3 N 5 , AlN, and NH 4 F. SrAl 5 P 4 N 10 O 2 F 3 crystallizes in space group I 4 ‾ m 2 ${I\bar 4m2}$ with a=11.1685(2) and c=7.84850(10) Å. Atomic-resolution EDX mapping with scanning transmission electron microscopy (STEM) indicates atom assignments, which are further corroborated by bond-valence sum (BVS) calculations. Ten Al 3+ -centered octahedra form a highly condensed tetra-face-capped octahedra-based unit that is a novel structure motif in network compounds. A network of vertex-sharing PN 4 tetrahedra and chains of face-sharing Sr 2+ -centered cuboctahedra complement the structure. Eu 2+ -doped SrAl 5 P 4 N 10 O 2 F 3 shows blue emission (λ em= 469 nm, fwhm=98 nm; 4504 cm -1 ) when irradiated with UV light., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Silicon pernitride, SiN 2 , was synthesized from the elements at 140 GPa in a laser-heated diamond anvil cell. Its crystal structure was solved and refined by means of synchrotron-based single-crystal X-ray diffraction data. The title compound crystallizes in the pyrite structure type (space group Pa , No. 205). The Si atom occupies a site with multiplicity 4 (Wyckoff letter b , site symmetry ..), while the N atom is located on a site with multiplicity 8 (Wyckoff letter c , site symmetry .3.). The crystal structure of SiN 2 is comprised of slightly distorted [SiN 6 ] octa-hedra inter-connected with each other by sharing vertices. Crystal chemical analysis of bond lengths suggests that Si has a formal oxidation state of +IV, while nitro-gen forms pernitride anions (N-N) 4- ., (© Jurzick et al. 2023.)

Oxonitridophosphates exhibit the potential for broad structural diversity, making them promising host-compounds in phosphor-converted light-emitting diode applications. The novel monophyllo-oxonitridophosphate β-MgSrP 3 N 5 O 2 was obtained by using the high-pressure multianvil technique. The crystal structure was solved and refined based on single-crystal X-ray diffraction data and confirmed by powder X-ray diffraction. β-MgSrP 3 N 5 O 2 crystallizes in the orthorhombic space group Cmme (no. 67, a=8.8109(6), b=12.8096(6), c=4.9065(3) Å, Z=4) and has a structure related to that of Ba 2 CuSi 2 O 7 . DFT calculations were performed to investigate the phase transition from α- to β-MgSrP 3 N 5 O 2 and to confirm the latter as the corresponding high-pressure polymorph. Furthermore, the luminescence properties of Eu 2+ doped samples of both polymorphs were investigated and discussed, showing blue and cyan emission, respectively (α-MgSrP 3 N 5 O 2 ; λ max =438 nm, fwhm=46 nm/2396 cm -1 ; β-MgSrP 3 N 5 O 2 ; λ max =502 nm, fwhm=42 nm/1670 cm -1 )., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Metal hydrides are an uprising compound class bringing up various functional materials. Due to the low X-ray scattering power of hydrogen, neutron diffraction is often crucial to fully disclose the structural characteristics thereof. We herein present the second strontium nitridoborate hydride known so far, Sr 13 [BN 2 ] 6 H 8 , formed in a solid-state reaction of the binary nitrides and strontium hydride at 950 °C. The crystal structure was elucidated based on single-crystal X-ray and neutron powder diffraction in the hexagonal space group P6 3 /m (no. 176), exhibiting a novel three-dimensional network of [BN 2 ] 3- units and hydride anions connected by strontium cations. Further analyses with magic angle spinning (MAS) NMR and vibrational spectroscopy corroborate the presence of anionic hydrogen within the structure. Quantum chemical calculations reveal the electronic properties and support the experimental outcome. Sr 13 [BN 2 ] 6 H 8 expands the emerging family of nitridoborate hydrides, broadening the access to an open field of new, intriguing materials., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Layered silicates are a very versatile class of materials with high importance to humanity. The new nitridophosphates MP 6 N 11 (M=Al, In), synthesized from MCl 3 , P 3 N 5 and NH 4 N 3 in a high-pressure high-temperature reaction at 1100 °C and 8 GPa, show a mica-like layer setup and feature rare nitrogen coordination motifs. The crystal structure of AlP 6 N 11 was elucidated from synchrotron single-crystal diffraction data (space group Cm (no. 8), a=4.9354(10), b=8.1608(16), c=9.0401(18) Å, β=98.63(3)°), enabling Rietveld refinement of isotypic InP 6 N 11 . It is built up from layers of PN 4 tetrahedra, PN 5 trigonal bipyramids and MN 6 octahedra. PN 5 trigonal bipyramids have been reported only once and MN 6 octahedra are sparsely found in the literature. AlP 6 N 11 was further characterized by energy-dispersive X-ray (EDX), IR and NMR spectroscopy. Despite the vast amount of known layered silicates, there is no isostructural compound to MP 6 N 11 as yet., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The Li + ion conductor Li 27-x [P 4 O 7+x N 9-x ]O 3 (x≈1.9) has been synthesized from P 3 N 5 , Li 3 N and Li 2 O in a Ta ampoule at 800 °C under Ar atmosphere. The cubic compound crystallizes in space group I 4 ‾ 3 d ${I\overline 4 3d}$ with a=12.0106(14) Å and Z=4. It contains both non-condensed [PO 2 N 2 ] 5- and [PO 3 N] 4- tetrahedra as well as O 2- ions, surrounded by Li + ions. Charge neutrality is achieved by partial occupancy of Li positions, which was refined with neutron powder diffraction data. Measurements of the partial ionic and electronic conductivity show a total ionic conductivity of 6.6×10 -8  S cm -1 with an activation energy of 0.46±0.02 eV and a bulk ionic conductivity of 4×10 -6  S cm -1 at 25 °C, which is close to the ionic conductivity of amorphous lithium nitridophosphate. This makes Li 27-x [P 4 O 7+x N 9-x ]O 3 an interesting candidate for investigation of structural factors affecting ionic conductivity in lithium oxonitridophosphates., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Invited for the cover of this issue are the groups of Oliver Oeckler at Leipzig University and Wolfgang Schnick at University of Munich (LMU). The image background depicts a diffraction pattern of an intergrown crystal containing P 40 O 31 N 46 as a night sky. P 40 O 31 N 46 and P 74 O 59 N 84 form complex disordered frameworks, a cutout of which symbolizes the earth's surface (which mainly contains silicates with related building blocks). The structures are built up from chain-like building units, which fall like rain, symbolizing the modular building scheme. Read the full text of the article at 10.1002/chem.202203892., (© 2023 Wiley-VCH GmbH.)

Non-crystalline lithium oxonitridophosphate (LiPON) is used as solid electrolyte in all-solid-state batteries. Crystalline lithium oxonitridophosphates are important model structures to retrieve analytical information that can be used to understand amorphous phases better. The new crystalline lithium oxonitridophosphate Li 5+x P 2 O 6-x N 1+x was synthesized as an off-white powder by ampoule synthesis at 750-800 °C under Ar atmosphere. It crystallizes in the monoclinic space group P2 1 /c with a=15.13087(11) Å, b=9.70682(9) Å, c=8.88681(7) Å, and β=106.8653(8)°. Two P(O,N) 4 tetrahedra connected by an N atom form the structural motif [P 2 O 6-x N 1+x ] (5+x)- . The structure was elucidated from X-ray diffraction data and the model corroborated by NMR and infrared spectroscopy, and elemental analyses. Measurements of ionic conductivity show a total ionic conductivity of 6.8×10 -7  S cm -1 at 75 °C with an activation energy of 0.52±0.01 eV., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Owing to their widespread properties, nitridophosphates are of high interest in current research. Explorative high-pressure high-temperature investigations yielded various compounds with stoichiometry MP 2 N 4 (M=Be, Ca, Sr, Ba, Mn, Cd), which are discussed as ultra-hard or luminescent materials, when doped with Eu 2+ . Herein, we report the first germanium nitridophosphate, GeP 2 N 4 , synthesized from Ge 3 N 4 and P 3 N 5 at 6 GPa and 800 °C. The structure was determined by single-crystal X-ray diffraction and further characterized by energy-dispersive X-ray spectroscopy, density functional theory calculations, IR and NMR spectroscopy. The highly condensed network of PN 4 -tetrahedra shows a strong structural divergence to other MP 2 N 4 compounds, which is attributed to the stereochemical influence of the lone pair of Ge 2+ . Thus, the formal exchange of alkaline earth cations with Ge 2+ may open access to various compounds with literature-known stoichiometry, however, new structures and properties., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Invited for the cover of this issue are Dominique Laniel (University of Edinburgh), Florian Trybel (University of Linköping), and their colleagues. The image depicts a bridge built of the newly discovered δ-P 3 N 5 solid with the structure featuring PN 6 units, a previously missing connection between the carbon group elements nitrides and chalcogens nitrides. Read the full text of the article at 10.1002/chem.202201998., (© 2022 Wiley-VCH GmbH.)

Combining different anions in one material allows tuning of its structural, magnetic, and electronic properties. We hereby present the mixed anion compound Sr 2 BN 2 H, expanding the less-known class of nitridoborate hydrides. Solid-state reaction of Sr 2 N, BN, and SrH 2 at 850 °C in a tube furnace yielded a gray, air- and moisture-sensitive powder of Sr 2 BN 2 H. It crystallizes as colorless platelets in the orthorhombic space group Pnma (no. 62) with a = 9.9164(2), b = 3.9079(1), and c = 10.1723(2) Å and Z = 4. An initial structural model was obtained from single-crystal X-ray diffraction data and corroborated by neutron powder diffraction data of the corresponding deuteride. Further validation by 1 H and 11 B MAS NMR, FTIR, and Raman spectroscopy complements the structural proof of anionic hydrogen present in the compound. Quantum chemical calculations support the experimental findings and reveal the electronic structure of Sr 2 BN 2 H.

The oxonitridosilicate La 7 Sr[Si 10 N 19 O 3 ] : Eu 2+ and its substitutional variants RE 8-x AE x [Si 10 N 20-x O 2+x ] : Eu 2+ with RE=La, Ce; AE=Ca, Sr, Ba and 0≤x≤2 were synthesized starting from REN, SrN/Ca 3 N 2 /Ba 2 N, SiO 2 , amorphous Si 3 N 4 and Eu 2 O 3 as doping agent at 1600 °C in a radiofrequency furnace. The crystal structure of La 7 Sr[Si 10 N 19 O 3 ] was solved and refined based on single-crystal X-ray diffraction data. La 7 Sr[Si 10 N 19 O 3 ] crystallizes in the orthorhombic space group Pmn2 1 (no. 31). The crystal structures of the isotypic compounds RE 8-x AE x [Si 10 N 20-x O 2+x ] were confirmed by Rietveld refinements based on powder X-ray diffraction data using the single-crystal data of La 7 Sr[Si 10 N 19 O 3 ] as starting point. Crystal structure elucidation reveals a 3D network of vertex sharing SiN 4 and SiN 2 (N 1/2-x/4 O 1/2+x/4 ) 2 (0≤x≤2) tetrahedra. When excited with UV to blue light, La 7 Sr[Si 10 N 19 O 3 ] : Eu 2+ shows amber luminescence with λ em =612 nm and fwhm=84 nm/2194 cm -1 , which makes it interesting for application in amber phosphor-converted light emitting diodes., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

In this work, we present a computational protocol that is able to predict the experimental absorption and emission spectral shapes of Eu 2+ -doped phosphors. The protocol is based on time-dependent density functional theory and operates in conjunction with an excited-state dynamics approach. It is demonstrated that across the study set consisting of representative examples of nitride, oxo-nitride, and oxide Eu 2+ -doped phosphors, the energy distribution and the band shape of the emission spectrum are related to the nature of the 4f-5d transitions that are probed in the absorption process. Since the 4f orbitals are very nearly nonbonding, the decisive quantity is the covalency of the 5d acceptor orbitals that become populated in the electronically excited state that leads to emission. The stronger the (anti) bonding interaction between the lanthanide and the ligands is in the excited state, the larger will be the excited state distortion. Consequently, the corresponding emission will get broader due to the vibronic progression that is induced by the structural distortion. In addition, the energy separation of the absorption bands that are dominated by states with valence 4f-5d and a metal to ligand charge transfer character defines a measure for the thermal quenching of the studied Eu 2+ -doped phosphors. Based on this analysis, simple descriptors are identified that show a strong correlation with the energy position and bandwidth of the experimental emission bands without the need for elaborate calculations. Overall, we believe that this study serves as an important reference for designing new Eu 2+ -doped phosphors with desired photoluminescence properties.

TiP 4 N 8 was obtained from the binary nitrides TiN and P 3 N 5 upon addition of NH 4 F as a mineralizer at 8 GPa and 1400 °C. An intricate interplay of disorder and polymorphism was elucidated by in situ temperature-dependent single-crystal X-ray diffraction, STEM-HAADF, and the investigation of annealed samples. This revealed two polymorphs, which consist of dense networks of PN 4 tetrahedra (degree of condensation κ=0.5) and either augmented triangular TiN 7 prisms or triangular TiN 6 prisms for α- and β-TiP 4 N 8 , respectively. The structures of TiP 4 N 8 exhibit body-centered tetragonal (bct) framework topology. DFT calculations confirm the measured band gaps of α- and β-TiP 4 N 8 (1.6-1.8 eV) and predict the thermochemistry of the polymorphs in agreement with the experiments., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The nitridoberylloaluminate Ba 2 [BeAl 3 N 5 ]:Eu 2+ and solid solutions Sr 2-x Ba x [BeAl 3 N 5 ]:Eu 2+ (x=0.5, 1.0, 1.5) were synthesized in a hot isostatic press (HIP) under 50 MPa N 2 atmosphere at 1200 °C. Ba 2 [BeAl 3 N 5 ]:Eu 2+ crystallizes in triclinic space group P 1 ‾ (no. 2) (Z=2, a=6.1869(10), b=7.1736(13), c=8.0391(14) Å, α=102.754(8), β=112.032(6), γ=104.765(7)°), which was determined from single-crystal X-ray diffraction data. The lattice parameters of the solid solution series have been obtained from Rietveld refinements and show a nearly linear dependence on the atomic ratio Sr : Ba. The electronic properties and the band gaps of M 2 [BeAl 3 N 5 ] (M=Sr, Ba) have been investigated by a combination of soft X-ray spectroscopy and density functional theory (DFT) calculations. Upon irradiation with blue light (440-450 nm), the nitridoberylloaluminates exhibit intense orange to red luminescence, which can be tuned between 610 and 656 nm (fwhm=1922-2025 cm -1 (72-87 nm)). In contrast to the usual trend, the substitution of the smaller Sr 2+ by larger Ba 2+ leads to an inverse-tunable luminescence to higher wavelengths. Low-temperature luminescence measurements have been performed to exclude anomalous emission., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)