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The impact of the surrounding ligand field is successfully exploited in the case of Eu2+ to tune the emission characteristics of inorganic photoactive materials with potential application in, e.g. phosphor‐converted white light‐emitting diodes (pc‐wLEDs). However, the photoluminescence of Mn2+ related to intraconfigurational 3d5–3d5 transitions is also strongly dependent on local ligand field effects and has been underestimated in this regard so far. In this work, we want to revive the idea how to electronically tune the emission color of a transition metal ion in inorganic hosts by unusual electronic effects in the metal‐ligand bond. The concept is explicitly demonstrated for the weakly coordinating layer‐like borosulfate ligand in the Mn2+‐containing solid solutions Zn1‐xMnx[B2(SO4)4] (x = 0, 0.03, 0.04, 0.05, 0.10). Zn[B2(SO4)4]:Mn2+ shows orange narrow‐band luminescence at 590 nm, which is an unusually short wavelength for octahedrally coordinated Mn2+ and indicates an uncommonly weak ligand field. On the other hand, the analysis of the interelectronic Racah repulsion parameters reveals ionic Mn−O bonds with values close to the Racah parameters of the free Mn2+ ion. Overall, this strategy demonstrates that electronic control of the metal‐ligand bond can be a tool to make Mn2+ a potent alternative emitter to Eu2+ for inorganic phosphors. [ABSTRACT FROM AUTHOR]

Red‐emitting narrow‐band phosphors are of utmost importance for next‐generation white‐light phosphor‐converted light‐emitting diodes (pc‐wLEDs) for improved efficacy and optimized correlated color temperatures. A promising representative crystallizing in an ordered variant of the UCr4C4 structure type is Sr[Li2Al2O2N2]:Eu2+ (SALON:Eu2+) emitting at a desirable wavelength of 614 nm. Despite an expected eightfold coordination of the Eu2+ ions by four N3− and O2− ions, respectively, the exact local coordination symmetry and a 1:1 ratio between the two types of ligands is not straightforwardly proven by X‐ray diffraction. Low‐temperature luminescence spectroscopy in conjunction with ligand field theory are powerful alternatives to resolve local features of Eu2+ as its excited 4f65d1 configuration reacts sensitively to the polarity of the ligands. The dominant emission at 614 nm shows pronounced vibronic fine structure at 10 K. In addition, weak emission bands can be resolved at 570 and 650 nm even at a low doping concentration of 0.5 mol% and are assigned to Eu2+ ions being eightfold coordinated by N3− and O2− ions in a ratio different from 1:1. Due to the feature of vierer ring‐type channels in SALON:Eu2+, those Eu2+ centers are sufficiently close for mutual energy transfer, which is characterized by time‐resolved luminescence at 10 K. [ABSTRACT FROM AUTHOR]

Some examples are I i - [[17]], I i - [[18], [19]], and I i -SrHPO SB 4 sb [[20]], Sr SB 5 sb (PO SB 4 sb ) SB 3 sb OH [[21]], and Sr SB 6 sb H SB 3 sb (PO SB 4 sb ) SB 5 sb -2H SB 2 sb O [[22]]. In contrast, the coordination environment and Ce-O bond lengths in I i -SrHPO SB 4 sb are expected to differ from those in Sr SB 5 sb (PO SB 4 sb ) SB 3 sb OH and I i -SrHPO SB 4 sb . S4 SP ‡ sp ), exemplary measurements before ( I t i = 1 min) and after ( I t i = 80 min) saturation were used to acquire the emission spectra of Ce SP 3+ sp -doped amorphous strontium phosphate, Sr SB 5 sb (PO SB 4 sb ) SB 3 sb OH, and I i -SrHPO SB 4 sb . It can be concluded that the coordination environment of the Ce SP 3+ sp ions in doped amorphous strontium phosphate is similar to that in doped Sr SB 5 sb (PO SB 4 sb ) SB 3 sb OH and I i -SrHPO SB 4 sb . [Extracted from the article]

Borosulfates are weakly coordinating ligands, which is directly reflected in the photoluminescence properties of the Mn SP 2+ sp ions: They show orange narrow emission, which is indicative for a weak octahedral ligand field, as explained by Jörn Bruns, Markus Suta et al. in their Research Article (e202309212). Borosulfates are weakly coordinating ligands, which is directly reflected in the photoluminescence properties of the Mn SP 2+ sp ions: They show orange narrow emission, which is indicative for a weak octahedral ligand field, as explained by Jörn Bruns, Markus Suta et al. in their Research Article (e202309212). Keywords: Borosulfate; Mn2+; Photolumineszenz; Schwach Koordinierend DE Borosulfate Mn2+ Photolumineszenz Schwach Koordinierend 1 1 1 10/31/23 20231106 NES 231106 B Mn b SP B 2+ b sp B b is a so-far still rather underestimated visible emitter that is more abundant than the currently dominantly used emitter Eu SP 2+ sp . [Extracted from the article]

• Transition metal, lanthanide, and actinide ions embedded in solids are prone to the surrounding ligand field. • Optical and magnetic properties of these elements are described by ligand field theory. • The angular overlap model (AOM) is chemically very intuitive and works with just a few parameters. • Several application areas of the AOM for f elements are discussed. Lanthanoid ions are well-known for their characteristic optical and magnetic properties interesting for a wide range of applications. Most of these properties show a subtle dependence on the surrounding ligands. Unlike the transition metal ions with their often encountered octahedral or tetrahedral coordination in compounds, rare earth ions are typically found in coordination geometries with low symmetries and high coordination numbers. The quantitative treatment of the ligand field in the so-called Wybourne scheme then becomes overparametrized and not readily insightful but merely a technical tool. In this review, we want to present the alternative approach by the chemically intuitive angular overlap model (AOM) of ligand field theory that is independent from symmetry and allows to decompose any coordination geometry into its separate metal–ligand bonds with well-known bonding character. It is the goal of this review to demonstrate its strength in the semi-quantitative description of opto-magnetic properties of the rare earth ions on carefully selected examples from practice. Finally, we compare the AOM to conventional Wybourne-parametrized ligand field theory and show how the two schemes of ligand field theory are related to one another. Overall, this review offers a perspective on future approaches to ligand field calculations with f elements with the benefit of full transparency and intuitive understanding rather than technical fitting. [ABSTRACT FROM AUTHOR]

Red‐emitting narrow‐band phosphors are of utmost importance for next‐generation white‐light phosphor‐converted light‐emitting diodes (pc‐wLEDs) for improved efficacy and optimized correlated color temperatures. A promising representative crystallizing in an ordered variant of the UCr4C4 structure type is Sr[Li2Al2O2N2]:Eu2+ (SALON:Eu2+) emitting at a desirable wavelength of 614 nm. Despite an expected eightfold coordination of the Eu2+ ions by four N3− and O2− ions, respectively, the exact local coordination symmetry and a 1:1 ratio between the two types of ligands is not straightforwardly proven by X‐ray diffraction. Low‐temperature luminescence spectroscopy in conjunction with ligand field theory are powerful alternatives to resolve local features of Eu2+ as its excited 4f65d1 configuration reacts sensitively to the polarity of the ligands. The dominant emission at 614 nm shows pronounced vibronic fine structure at 10 K. In addition, weak emission bands can be resolved at 570 and 650 nm even at a low doping concentration of 0.5 mol% and are assigned to Eu2+ ions being eightfold coordinated by N3− and O2− ions in a ratio different from 1:1. Due to the feature of vierer ring‐type channels in SALON:Eu2+, those Eu2+ centers are sufficiently close for mutual energy transfer, which is characterized by time‐resolved luminescence at 10 K. [ABSTRACT FROM AUTHOR]

Some examples are I i - [[17]], I i - [[18], [19]], and I i -SrHPO SB 4 sb [[20]], Sr SB 5 sb (PO SB 4 sb ) SB 3 sb OH [[21]], and Sr SB 6 sb H SB 3 sb (PO SB 4 sb ) SB 5 sb -2H SB 2 sb O [[22]]. In contrast, the coordination environment and Ce-O bond lengths in I i -SrHPO SB 4 sb are expected to differ from those in Sr SB 5 sb (PO SB 4 sb ) SB 3 sb OH and I i -SrHPO SB 4 sb . S4 SP ‡ sp ), exemplary measurements before ( I t i = 1 min) and after ( I t i = 80 min) saturation were used to acquire the emission spectra of Ce SP 3+ sp -doped amorphous strontium phosphate, Sr SB 5 sb (PO SB 4 sb ) SB 3 sb OH, and I i -SrHPO SB 4 sb . It can be concluded that the coordination environment of the Ce SP 3+ sp ions in doped amorphous strontium phosphate is similar to that in doped Sr SB 5 sb (PO SB 4 sb ) SB 3 sb OH and I i -SrHPO SB 4 sb . [Extracted from the article]