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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.

The program BonnMag has been developed to calculate the absorption spectra and temperature dependent magnetic susceptibilities of f(n) systems. The computations of the transition energies are performed within the angular overlap model. Using Judd-Ofelt theory BonnMag allows estimation of the relative absorption coefficients of the electronic transitions with reasonable accuracy. A description of the theoretical background of the implemented methods is given. Using Slater-Condon-Shortley parameters and spin-orbit coupling coefficients for free Ln(3+) ions from ab initio calculations, the transition energies of all Ln(3+) ions are calculated and compared to the results from CASSCF/NEV-PT2 calculations. Splitting due to the ligand field as well as transition energies of all Cs(2)NaLnCl(6) (except Gd and Pm) are calculated using parameters reported in the literature. Based on the comparison between theory and experiment, the potential and limitations of the program BonnMag are shown. (c) 2017 Wiley Periodicals, Inc.

This work concerns a novel blue emitting LED phosphor activated by Eu2+. It was found that this luminescent material can be efficiently pumped by near UV or UV-A radiation sources while it exhibits a high quantum yield at a doping level between 0.3 and 3.0%. More impressively, this material has a very high quenching temperature T1/2 and will thus be applicable on-chip in high power phosphor converted LEDs or even in laser diodes. The emission and thermal stability are almost identical to that of BAM:Eu2+ while the absorption band is broader and reaches into the near UV range. Therefore, Na3RbMg7(PO4)6:Eu2+ is a promising candidate as a blue emitter in high CRI full conversion LEDs. To investigate the site preference of Eu2+, DFT and Ligand Field Theory based calculations were performed to successfully predict the emission spectrum. An unusual decay behavior was observed at low temperatures and the underlying mechanism involving spin-forbidden transitions of Eu2+ is discussed., The authors want to thank Merck KGaA, Darmstadt, Germany for their generous financial support.

Detailed experimental data on UPO4Cl comprising single-crystal UV/vis/NIR spectra and temperature-dependent magnetic susceptibilities form the basis for the investigation of the electronic structure of the U(4+) cation in UPO4Cl. For modeling of the observed physical properties the angular overlap model (AOM) was successfully employed. The computations were performed using the newly developed computer program BonnMag. The calculations show that all electronic transitions and the magnetic susceptibility as well as its temperature dependence are well-reproduced within the AOM framework. Using Judd-Ofelt theory BonnMag allows estimation of the relative absorption coefficients of the electronic transitions with reasonable accuracy. Ligand field splitting for states originating from f-electron configurations are determined. Slater-Condon-Shortley parameters and the spin-orbit coupling constant for U(4+) were taken from literature. The good transferability of AOM parameters for U(4+) is confirmed by calculations of the absorption spectra of UP2O7 and (U2O)(PO4)2. The effect of variation of the fit parameters is investigated. AOM parameters for U(4+) (5f) are compared to those of the rare-earth elements (4f) and transition metals (3d).

Emerald-green single crystals of U(PO4)Cl were grown by chemical vapor transport in a temperature gradient (1000 → 900 °C). The crystal structure of U(PO4)Cl (Cmcm, Z = 4, a = 5.2289(7) Å, b = 11.709(2) Å, c = 6.9991(8) Å) consists of a three-dimensional network of [PO4] tetrahedra and bicapped octahedral [U(IV)O6Cl2] groups. Polarized absorption spectra measured for two perpendicular polarization directions show a large number of well-resolved electronic transitions. These transitions can be fully assigned on the basis of a detailed ligand-field treatment within the framework of the angular overlap model. The magnetic behavior predicted on the basis of the spectroscopic data is in agreement with an f (2) system and perfectly matched by the results of temperature-dependent susceptibility measurements.

Producción Científica, We present here our theoretical model that allows to predict, for the first time, the luminescence properties of a new phosphor (BaSnSi3O9:Eu2+) before the experiment is performed. The predicted emission wavelength, 488 nm with a 64 nm bandwidth, is confirmed by subsequent experimental work. The method consists in a multielectronic Hamiltonian parametrized from ab initio calculations. The luminescence properties of other similar compounds (BaHfSi3O9:Eu2+ and BaZrSi3O9:Eu2+), for which there is already experimental information, are also correctly reproduced., Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI) (grant PCE 108/2017), Merck KGaA, Germany, Junta de Castilla y León (Project VA124G18)

The most efficient way to provide domestic lighting nowadays is by light-emitting diodes (LEDs) technology combined with phosphors shifting the blue and UV emission toward a desirable sunlight spectrum. A route in the quest for warm-white light goes toward the discovery and tuning of the lanthanide-based phosphors, a difficult task, in experimental and technical respects. A proper theoretical approach, which is also complicated at the conceptual level and in computing efforts, is however a profitable complement, offering valuable structure-property rationale as a guideline in the search of the best materials. The Eu(2+)-based systems are the prototypes for ideal phosphors, exhibiting a wide range of visible light emission. Using the ligand field concepts in conjunction with density functional theory (DFT), conducted in nonroutine manner, we develop a nonempirical procedure to investigate the 4f(7)-4f(6)5d(1) luminescence of Eu(2+) in the environment of arbitrary ligands, applied here on the CsMgBr3:Eu(2+)-doped material. Providing a salient methodology for the extraction of the relevant ligand field and related parameters from DFT calculations and encompassing the bottleneck of handling large matrices in a model Hamiltonian based on the whole set of 33,462 states, we obtained an excellent match with the experimental spectrum, from first-principles, without any fit or adjustment. This proves that the ligand field density functional theory methodology can be used in the assessment of new materials and rational property design.

The flux growth of uranium(IV) oxides presents several challenges, and to the best of our knowledge, only one example has ever been reported. We succeeded in growing two new reduced uranium silicates A2USi6O15 (A = K, Rb) under flux growth conditions in sealed copper tubes. The compounds crystallize in a new structure type with space group C2/c and lattice parameters a = 24.2554(8) Å, b = 7.0916(2) Å, c = 17.0588(6) Å, β = 97.0860(6) ° (K) and a = 24.3902(8) Å, b = 7.1650(2) Å, c = 17.2715(6) Å, β = 96.8600(6) ° (Rb). A2USi6O15 (A = K, Rb) are isocompositional to a previously reported Cs2USi6O15, and the two structures are compared. K2USi6O15 undergoes an interesting crystal-to-crystal structural phase transition at T ≈ 225 K to a triclinic structure, which is accompanied by an intense color change. The magnetic properties of A2USi6O15 (A = K, Rb, Cs) are reported and differ from the magnetism observed in other U(4+) compounds. Calculations are performed on the (UO6)(-8) clusters of K2USi6O15 to study the cause of these unique magnetic properties.

The theoretical rationalization of the open-shell 4f and 5d configuration of Eu 2+ is by far not trivial because it involves a non-standard version of ligand field theory, based on a two-shell Hamiltonian. Here we present our methodology based on ligand field theory, taking the system CsCaBr 3 :Eu 2+ as a case study with an octahedral coordination sphere of Eu 2+ . The ligand field, interelectronic and spin-orbit coupling parameters are deduced from experimental data. The assignment of the transitions to the corresponding irreducible representations of the double group was performed together with the intensity modelling resulting in an excellent match to the experimental spectra.

We present a theoretical work detailing the electronic structure and the optical properties of (PrF8)(5-) embedded in LiYF4, complementing the insight with data that are not available by experimental line. The local distortions due to the embedding of the lanthanide ion in the sites occupied in the periodic lattice by smaller yttrium centres, not detectable in regular X-ray analyses, are reproduced with the help of geometry optimization. Then, based on the local coordination environment, the relation structure-optical properties is constructed by Density Functional Theory computations in conjunction with the ligand field theory analyses (LFDFT) determining the [Xe]4f(2)→ [Xe]4f(1)5d(1) transitions. In previous instances we analysed rather symmetric systems, here facing the complexity of low symmetry cases, treated in the Wybourne ligand field parameterization and in the Angular Overlap Model (AOM) frame. A very important improvement at the AOM level is the consideration of the f-d mixing that brings coupling term of odd-even nature, essential for the realistic description of the asymmetric coordination centres. Furthermore, we introduce now a principle for modelling the emission intensity. The results are in agreement with available experimental findings. The relevance of the modelling has a practical face in the rational design of optimal luminescent materials needed in domestic lightening and also an academic side, revisiting with modern computational tools areas incompletely explored by the standard ligand field theories.

In this work, we predict and measure the optical behaviour of Pr 3+ in different binary and ternary fluorides. We use a validated model based on Ligand Field Theory and Density Functional Theory to calculate the multiplet energy levels arising from the ground [Xe]4f 2 and excited [Xe]4f 1 5d 1 electron configurations of Pr 3+ in its chemical environment. Moreover, the luminescence spectra of the considered materials were recorded. In overall the theoretical determination corroborates to the experimental findings. The phenomenon of the photon cascade emission is particularly stressed, being important for the design of modern phosphors with quantum efficiencies larger than 100%.

Here we report a theoretical analysis of the luminescence properties of Sr2Si5N8 host lattices codoped with Ca(2+) and Eu(2+). These systems have been first synthesized by Li et al. [J. Solid State Chem., 2008, 181, 515], who have found that Ca(2+) doping provokes a red-shifting of the emission peak of Eu(2+), from 620 nm to 643 nm. However, the mechanism that drives this shift is still unclear from experimental data. Based on density functional theory and ligand field analysis, we study the structure, stability, and emission properties of Eu(2+) embedded in the (Sr1-xCax)2Si5N8 host lattice. Our results provide a full explanation of the experimental data and the methodology could constitute a valuable tool for the design of phosphors with tunable emission spectra.

We present a recipe for the calculation of the optical properties of Ce 3+ -doped systems. The model implies the use of ligand field phenomenology in conjunction with Density Functional Theory (DFT). The particular procedures enable the reliable prediction of the 4f 1 → 4f 0 5d 1 transitions in Cs 2 NaYCl 6 :Ce 3+ . The analysis of the doping of Ce 3+ into the host is accomplished by band structure calculations. The calculated multiplet energy levels are in agreement with the experimental observation, the outlined treatment being, to the best of our knowledge, unprecedented clear and conclusive application of DFT for the rather complex problems of structure and spectroscopy of cerium-doped systems.

The new ternary compounds UP2S6, UP2S7, U(P2S6)2, and U3(PS4)4 were prepared from uranium metal, phosphorus pentasulfide, and sulfur at 700 °C. The crystal structures were determined by single-crystal X-ray diffraction methods. UP2S6 (I) crystallizes in the ZrP2S6 structure type [tetragonal, P42/m, a = 6.8058(7) A, c = 9.7597(14) A, Z = 2], which consists of central uranium(IV) atoms coordinated by P2S64– anions (staggered conformation). The anions are two-dimensional connectors for four uranium cations arranged in one plane. The structure of UP2S7 (II) [orthorhombic, Fddd, a = 8.9966(15) A, b = 15.2869(2) A, c = 30.3195(5) A, Z = 16] is closely related to the monoclinic ZrP2S7 structure type. It consists of U4+ cations linked by P2S74– ligands, the resulting 3D network contains large pores (diameter approx. 3.5 × 16.7 A). In the previously reported compound U(P2S6)2 (III) [I41/a, a = 12.8776(9) A, c = 9.8367(10) A, Z = 2], the metal atoms are coordinated by four bidentate P2S62– ligands. This arrangement can be considered as a pseudotetrahedral coordination of the uranium atoms by the linear ligands. Three of the resulting diamondoid frameworks are inseparably interwoven in order to optimize space filling. U3(PS4)4 (IV) [I41/acd, a = 10.7440(9) A, c = 19.0969(2) A, Z = 2] crystallizes in a defect variant of the PrPS4 structure type, with 50 % of the U2 sites statistically occupied with uranium atoms. The resulting stoichiometry is U3(PS4)4 with tetravalent uranium atoms. The structure of U3(PS4)4 consists of uranium atoms connected by PS43– groups, each PS4 group linking four central uranium atoms. Vibrational spectra, which were recorded for I–III, show good agreement between the obtained results and the expected values for the anionic units, while magnetic measurements confirm the presence of tetravalent uranium.

The Yb(2+)-doped perovskite derivatives CsMX3 (M = Ca and Sr; X = Cl, Br, and I) are ideal systems for obtaining a detailed insight into the structure-luminescence relationship of divalent lanthanides. The investigation of the respective photoluminescence properties yielded two emission bands in the violet and blue spectral range for all compounds, which are assigned to the spin-allowed and spin-forbidden 5d-4f transitions, respectively. The impact on their energetic positions is dependent on both the covalency of the Yb(2+)-halide bond and the corresponding bond length in agreement with expectations. The excitation spectra provide a detailed fine structure at low temperatures and can be partly interpreted separating the 4f(13) core from the 5d electron in the excited state. The local crystal field in CsSrI3:Yb(2+) provides a special case due to the trigonal distortion induced by the crystal structure that is clearly evident in the luminescence features of Yb(2+). The structure-property relationship of several spectroscopic key quantities of Yb(2+) in this series of halides is analyzed in detail and parallels the properties of Eu(2+) ions doped in the given perovskites.

The novel tetrameric gadolinium(III) compound [Gd4(OH)4(CF3COO)8(H2O)4] · 2.5 H2O was synthesized and structurally characterized by X-ray crystallography. The Gd3+ ions are bridged by hydroxide ions and carboxylate groups to tetramers with Gd3+-Gd3+ distances between 384.2(2) and 388.1(2) pm. The compound crystallizes in the monoclinic space group C2/c (Z = 4). The magnetic behaviour of [Gd4(OH)4(CF3COO)8(H2O)4] · 2.5 H2O was investigated in the temperature range of 2 to 300 K. The magnetic data of this compound indicate antiferromagnetic interactions (Jex = −0.0197 cm−1).

The compounds M2USi6O15 (M: K, Rb, Cs) are prepared in 61, 29, and 37% yield, resp., by layering a mixture of UO2 and SiO2 under a MF/MCl mixture that acts as a flux (copper tube, N2 flow, 900 °C, 12 h).

Four complexes with the formulae Gd2(ClF2CCOO)6(hypy)2 (1), Gd2(F3CCOO)6(hypy)2 (2), Gd2(F2HCCOO)6(hypy)2 (3) and Gd2(Cl2HCCOO)6(H2O)2(hypy)2 (4) have been synthesised and characterised by single-crystal X-ray diffraction methods at room temperature. The title compounds have been obtained by reaction of the corresponding gadolinium carboxylates with 4-hydroxypyridine in a solution of ethanol and water. They crystallise in the triclinic space group P (Z = 2) [1: a = 999.8(4) pm, b = 1061.8(5) pm, c = 1283.6(6) pm, α = 91.23(5)°, β = 111.29(5)° and γ = 105.27(5)°; 2: a = 972.4(4) pm, b = 1053.5(5) pm, c = 1252.4(6) pm, α = 94.23(5)°, β = 110.21(5)° and γ = 104.84(5)°; 3: a = 883.3(4) pm, b = 1051.3(4) pm, c = 1284.9(6) pm, α = 100.46(5)°, β = 109.87(5)° and γ = 97.43(5)°; 4: a = 913.7(4) pm, b = 1079.0(5) pm, c = 1137.5(5) pm, α = 93.41(5)°, β = 109.36(5)° and γ = 99.53(5)°]. The crystal structures consist of dinuclear Gd3+–Gd3+ units. The corresponding residuals (all data) for the refined structures are 4.82 % (1), 5.93 % (2), 5.68 % (3) and 4.04 % (4). The magnetic behaviour of the compounds was investigated over the temperature range 1.76–300 K. The magnetic data were interpreted by considering exchange interactions within the dimeric units [Jex = –0.019 cm–1 (1), Jex = –0.034 cm–1 (2), Jex = –0.064 cm–1 (3), Jex = –0.011 cm–1 (4)].(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The gadolinium(III) trifluoroacetates ((CH3)2NH2)[Gd(CF3COO)4] (1), ((CH3)3NH)[Gd(CF3 COO)4(H2O)] (2), Gd(CF3COO)3(H2O)3 (3) as well as Gd2(CF3COO)6(H2O)2(phen)3 · C2H5OH (4) (phen = 1,10-phenanthroline) were synthesized and structurally characterized by X-ray crystallography. These compounds crystallize in the space group P1̅ (No. 2, Z = 2) (1, 2 and 4) and P 21/c (No. 14, Z = 4) (3), respectively, with the following lattice constants 1: a = 884.9(2), b = 1024.9(2), c = 1173.1(2) pm, α = 105.77(2), β = 99.51(2), γ = 107.93(2)°; 2: a = 965.1(1), b = 1028.6(1), c = 1271.3(2) pm, α = 111.83(2), β = 111.33(2), γ = 90.44(2)°; 3: a = 919.6(2), b = 1890.6(4), c = 978.7(2) pm, β = 113.94(2)°; 4: a = 1286.7(8), b = 1639.3(8), c = 1712.2(9) pm, α = 62.57(6), β = 84.13(5), γ = 68.28(5)°. The compounds consist of Gd3+ ions which are bridged by carboxylate groups either to chains (1 and 2) or to dimers (3 and 4). In addition to the Gd3+ dimers, compound (4) also contains monomeric Gd3+ units. The magnetic behaviour of 2 and 3 was investigated in a temperature range of 1.77 to 300 K. The magnetic data for these compounds indicate weak antiferromagnetic interactions

Synthesis, Crystal Structure and Magnetic Behaviour of Gd(CF3CF2COO)3(H2O)3 Single crystals of Gd(CF3CF2COO)3(H2O)3 have been obtained by reaction of Gd2O3 with an aqueous solution of CF3CF2COOH. The compound crystallizes triclinically in the space group (No. 2; Z = 2; a = 928.5(1) pm, b = 1037.1(1) pm, c = 1147.3(2) pm, α = 90.44(2)°, β = 108.56(1)°, γ = 106.49(1)°). In the crystal structure the gadolinium ions are bridged by carboxylate groups to dimers and are coordinated eightfold by oxygen atoms. The magnetic behaviour was investigated in the temperature range of 1.77 to 300 K. The magnetic data indicate weak antiferromagnetic interactions within the dimeric unit (Jex = −0.0057 cm−1).

The three novel gadolinium(III) containing compounds (NH3CH3)[Gd(CF3CF2COO)4(H2O)] (1), (NH3C2H5)[Gd(CF3CF2COO)4(H2O)] (2) and ((CH3)4N)[Gd(CF3CF2COO)3(H2O)2]CF3CF2COO (3) were synthesized and structurally characterized by X-ray crystallography. In the crystal structures of 1 and 2, the gadolinium ions are bridged by carboxylate groups to dimers with a Gd3+–Gd3+ distance of 451.6(2) (1) and 451.8(3) pm (2), respectively. In the crystal structure of 3 the Gd3+ ions are bridged by carboxylate groups to chains with almost the same Gd3+–Gd3+ distances (494.0(8) and 503.4(7) pm). The magnetic behaviour of 1 and 2 was investigated in the temperature range of 1.76–300 K. The magnetic data indicate weak antiferromagnetic interactions within the dimeric unit.

Single crystals of [NH3C2H5][Gd(Cl2HCCOO)4] have been obtained by reaction of Gd2O3 with NH3C2H5Cl in an aqueous solution of Cl2HCCOOH. The compound crystallizes in the triclinic space group P 1 ¯ (no. 2, Z = 2, a = 813.7(3) pm, b = 1246.9(4) pm, c = 1263.9(4) pm, α = 61.67(4)°, β = 87.39(4)°, γ = 84.84(4)°). The Gd3+ ion is eight-fold coordinated by oxygen atoms. The magnetic behavior of the compound was investigated in the temperature range of 1.72–300 K. The magnetic data indicate an intramolecular ferromagnetic interaction within a dimeric unit (Jintra = + 0.029 cm−1) on which an intermolecular antiferromagnetic interaction is imposed (Jinter = −0.010 cm−1).

Single crystals of the title compound have been obtained by reaction of Gd3(ClH2CCOO)9(H2O)5 with 2,2′-bipyridyl (bipy) in a solution of ethanol and water. Gd2(ClH2CCOO)6(bipy)2 crystallises in the triclinic space group P (Z = 2) with a = 959.5(3) pm, b = 980.9(3) pm, c = 1163.9(4) pm, α = 68.67(3) °, β = 84.82(4)° and γ = 82.47(4)°. The crystal structure is built up of discrete molecules of dinuclear Gd3+–Gd3+ units. The corresponding residual (all data) for the refined structure is 4.46 %. The magnetic behaviour of the compound was investigated in the temperature range of 1.76–300 K. The magnetic data were interpreted considering exchange interactions within the dimeric unit (Jex = –0.020 cm–1). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Single crystals of Gd2(Cl3CCOO)6(bipy)2 × (H2O)2 · 4 bipy, Pr(Cl3CCOO)3(bipy)2, Nd(Cl3CCOO)3 × (bipy)2 and Er(Cl3CCOO)3(bipy)2(H2O) have been obtained by reaction of the corresponding trichloroacetate salts with 2,2′-bipyridyl (bipy) in a water/ethanol (1:1) solution. Gd2(Cl3CCOO)6(bipy)2(H2O)2 · 4 bipy crystallizes in the monoclinic space group P21/c (no. 14, Z = 4, a = 1642.40(9) pm, b = 1227.36(10) pm, c = 2303.48(14) pm, β = 107.043(7)°). The Gd3+ ions are bridged to dimers by carboxylate groups and are surrounded by six oxygen and two nitrogen atoms. One 2,2′-bipyridyl molecule is coordinated to Gd3+, the two other ones are non-coordinated. The monomeric compounds Ln(Cl3CCOO)3(bipy)2 (Ln = Pr, Nd) are isotypic with each other and crystallize in the triclinic space group P-1 (no. 2, Z = 2, Pr: a = 989.83(8) pm, b = 1032.22(8) pm, c = 1791.56(13) pm, α = 99.312(9)°, β = 102.036(9)°, γ = 99.166(9)°; Nd: a = 990.09(7) pm, b = 1030.74(8) pm, c = 1788.70(13) pm, α = 99.393(9)°, β = 102.064(8)°, γ = 99.242(9)°). The Ln3+ atom is surrounded by six oxygen and four nitrogen atoms. A chelating coordination by the carboxylate groups is observed. There are two 2,2′-bipyridyl molecules coordinated to Ln3+. The compound Er(Cl3CCOO)3(bipy)2(H2O) crystallizes in the triclinic space group P-1 (no. 2, Z = 2, a = 1060.65(9) pm, b = 1273.35(11) pm, c = 1402.49(11) pm, α = 105.484(10)°, β = 104.504(9)°, γ = 93.712(10)°). The Er3+ ion is coordinated by four oxygen and four nitrogen atoms. There are two 2,2′-bipyridyl molecules attached to Er3+.

Einkristalle von [NH3CH3][Gd(Cl2HCCOO)4] wurden durch Reaktion von Gd2O3 mit NH3CH3Cl in einer wassrigen Losung von Cl2HCCOOH erhalten. Die Verbindung kristallisiert triklin in der Raumgruppe P 1¯ (Nr. 2, Z = 2, a = 811, 5 pm, b = 1228, 4 pm, c = 1228, 9 pm, α = 62, 43°, β = 87, 67°, γ = 84, 48°). Die Gd3+-Ionen sind durch Carboxylatgruppen zu Ketten verknupft. Diese kann man sich aus dimeren Einheiten aufgebaut denken, da zwei unterschiedliche Gd3+-Gd3+-Abstande auftreten. Das magnetische Verhalten der Verbindung wurde im Temperaturbereich von 1, 77 bis 300 K untersucht. Die magnetischen Daten weisen auf eine intramolekulare ferromagnetische Wechselwirkung in der dimeren Einheit hin (Jintra = +0, 023 cm-1), die von einer intermolekularen antiferromagnetischen Wechselwirkung uberlagert wird (Jinter = -0, 007 cm-1). Synthesis, Crystal Structure and Magnetic Behaviour of [NH3CH3][Gd(Cl2HCCOO)4] Single crystals of [NH3CH3][Gd(Cl2HCCOO)4] have been obtained by reaction of Gd2O3 with NH3CH3Cl in an aqueous solution of Cl2HCCOOH. The compound crystallizes in the triclinic space group P 1¯ (No. 2, Z = 2, a = 811.5 pm, b = 1228.4 pm, c = 1228.9 pm, α = 62.43°, β = 87.67°, γ = 84.48°). The Gd3+ ions are connected to chains by carboxylate groups. The chains can be considered to consist of dimeric units as two different Gd3+-Gd3+ distances appear. The magnetic behaviour of the compound was investigated in the temperature range of 1.77 to 300 K. The magnetic data indicate an intramolecular ferromagnetic interaction within the dimeric unit (Jintra = +0.023 cm-1) on which an intermolecular antiferromagnetic interaction is imposed (Jinter = -0.007 cm-1).

Rules are pointed out to protect the magnetochemist from pitfalls in both measurement and interpretation of magnetic data. Carefully chosen magnetic field strengths during magnetic susceptibility measurements guarantee the recording of genuine data. With the help of examples, the effect of too strong applied fields is demonstrated producing magnetic saturation and, for example, quenching of weak ferro- or antiferromagnetic spin–spin couplings. In consequence, the data run the risk of being misinterpreted unless model susceptibility equations are applied that take the field dependence of χ m into consideration. Recommendations are given for the presentation of experimental and theoretical data. The limited applicability of the most overworked formula in paramagnetism, the Curie–Weiss law χ m = C/(T–θ), is clearly presented (magnetically condensed systems, pure spin magnetism). While rough and ready susceptibility formulae are applicable to specific 3d and 4f systems, the complex situation for the remaining d and f centers, including actinides, demands computer programs which consider simultaneously interelectronic repulsion, ligand field potential, spin-orbit coupling, interatomic exchange interactions, and applied magnetic field.

Einkristalle von Ln(ClF2CCOO)3(H2O)3 (Ln = Gd, Dy, Ho, Er) wurden durch Reaktion von Ln2O3 mit einer wassrigen Losung von ClF2CCOOH erhalten. Die Verbindungen sind isotyp miteinander und kristallisieren monoklin in der Raumgruppe P 21/c (Nr.: 14; Z = 4) mit den Gitterkonstanten, z.B. Gd(ClF2CCOO)3(H2O)3: a = 927, 9(3) pm, b = 1923, 8(4) pm, c = 1037, 2(4) pm, β = 114, 21(4)°. In den Kristallstrukturen sind die Lanthanidionen durch Carboxylatgruppen zu dimeren Einheiten verbruckt und von Sauerstoffatomen achtfach koordiniert. Das magnetische Verhalten von Gd(ClF2CCOO)3(H2O)3 wurde im Temperaturbereich von 1, 73 bis 300 K untersucht. Die magnetischen Daten weisen auf eine schwache antiferromagnetische Wechselwirkung in der dimeren Einheit hin. Synthesis and Crystal Structures of Ln(ClF2CCOO)3(H2O)3 (Ln = Gd, Dy, Ho, Er) and Magnetic Behaviour of Gd(ClF2CCOO)3(H2O)3 Single crystals of Ln(ClF2CCOO)3(H2O)3 (Ln = Gd, Dy, Ho, Er) have been obtained by reaction of Ln2O3 with an aqueous solution of ClF2CCOOH. The compounds are isotypic with each other and crystallize monoclinically in the space group P 21/c (No. 14; Z = 4) with the following lattice constants, e.g. Gd(ClF2CCOO)3(H2O)3: a = 927.9(3) pm, b = 1923.8(4) pm, c = 1037.2(4) pm, β = 114.21(4)°. In the crystal structures the lanthanide ions are bridged by carboxylate groups to dimers and are eightfold coordinated by oxygen atoms. The magnetic behaviour of Gd(ClF2CCOO)3(H2O)3 was investigated in the temperature range of 1.73 to 300 K. The magnetic data indicate weak antiferromagnetic interactions within the dimeric unit.

Single crystals of Gd(HF 2 CCOO) 3 (H 2 O) 2 .H 2 O have been obtained by reaction of Gd 2 O 3 with HF 2 CCOOH in water. Data collection was carried out using a STOE imaging plate diffractometer at 173 K. The compound crystallizes in the triclinic space group P1 (Z = 2) with a = 833.1(2) pm, b = 943.5(2) pm, c = 944.9(2) pm; a = 66.78(3), β = 79.54(3) and y = 77.61(3). The corresponding residual (all data) for the refined structure is 2.98%. The magnetic behaviour of the compound was investigated in the temperature range of 1.7-300 K. The magnetic data were interpreted considering exchange interaction effects in the dinuclear Gd 3+ -Gd 3+ unit. The exchange coupling constant J = -0.024 cm -1 indicates antiferromagnetic interaction, whereas J = +0.05 cm -1 for Gd(H 3 CCOO) 3 (H 2 O) 2 .2H 2 O a ferromagnetic one.

The magnetism of the three compounds Pr 3 X[SiS 4 ] 2 (X=Cl, Br, I) has been measured in the temperature range between 1.7 and 300 K. For the theoretical calculations to interpret the magnetic behavior the angular overlap model was employed to reproduce the ligand field influence and the molecular field approach to take magnetic interaction into account.

Single crystals of the title compound were prepared from the elements by a solid state reaction in an iodine atmosphere. Data collection were carried out using a STOE image plate detector at 293 K. The compound crystallizes in the space group P 2 1 /n of the monoclinic system isotypically to Tb 4 [SiS 4 ] 3 with four formular units in cells of dimensions: a =986.7(2) pm, b =1099.69(19) pm, c =1646.2(4) pm, β =102.67(3)°. The corresponding residual (all data) for the refined structure is 3.09%. The magnetic behavior of the compound was investigated on powdered samples in a temperature range between 1.7 and 300 K. The deviations from the Curie-behavior could be interpreted by the molecular field approach.

Single crystals of Nd3ClS2[SiS4] were prepared from the elements. Data collection was carried out using a STOE image plate detector at 293 K. The compound crystallizes in the orthorhombic space group Pnma with eight familiar units in a cell of dimension: a=1240.3(2),b=1035.8(2),c=1616.4(3) pm The corresponding residual (all data) for the refined structures is 3.45%. In the crystal structure, the chloride ions form chains along [0 1 0] with trigonal coordination by the lanthanide ions. The magnetic behavior of powdered crystals was interpreted by ligand field calculations where the influence of the ligand field was taken into account by applying the angular overlap model and magnetic exchange by the molecular field approximation.

Kristalle des komplexen Chlorides (2,4,6-Trimethylpyridinium)10[ErCl6][ErCl5(H2O)]2Cl3 wurden durch Reaktion von ErCl3·6H2O mit 2,4,6-Trimethylpyridiniumchlorid in ethanolischer Losung dargestellt und die Kristallstruktur anhand von rontgenographischen Einkristalldaten ermittelt. Die Verbindung kristallisiert monoklin in der Raumgruppe P21/a (Z = 2) mit den Gitterparametern a = 1704, 5(3) pm, b = 1696, 7(2) pm, c = 1798, 5(4) pm und β = 90, 76(3)°. In der Kristallstruktur liegen oktaedrische Koordinationspolyeder der Zusammensetzung [ErCl6]3— und [ErCl5(H2O)]2— vor. Die Oktaeder sind uber Wasserstoff brucken bindungen mit den organischen Kationen und den isolierten Chlorid-Anionen zu Schichten parallel (0 1 0) verknupft. Die Ergebnisse magnetischer Messungen an Pulverproben der Titelverbindung konnten mit Hilfe ligandenfeldtheoretischer Rechnungen unter Anwendung des Angular-Overlap-Modells interpretiert werden. Preparation, Crystal Structure, and Magnetic Behaviour of (2,4,6-Trimethylpyridinium)10[ErCl6][ErCl5(H2O)]2Cl3 Crystals of the complex chloride (2,4,6-Trimethylpyridinium)10[ErCl6][ErCl5(H2O)]2Cl3 have been prepared by reaction of ErCl3·6H2O with 2,4,6-Trimethylpyridiniumchloride in ethanol solution for the first time. The crystal structure has been determined from single crystal X-ray diffraction data. The compound crystallizes monoclinically in the space group P21/a (Z = 2) with a = 1704.5(3) pm, b = 1696.7(2) pm, c = 1798.5(4) pm and β = 90.76(3)°. The structure contains octahedral building units [ErCl6]3— and [ErCl5(H2O)]2—. The octahedra, the organic cations and isolated chloride anions are interconnected via hydrogen bonds forming layers parallel to the ac-plane (0 1 0). The magnetic behaviour of (2,4,6-Trimethylpyridinium)10[ErCl6][ErCl5(H2O)]2Cl3 has been studied. The magnetic data are interpreted by ligand field calculations applying the angular overlap model.

The complex chloride (2-methylpyridinium)2[TbCl4(H2O)3]Cl has been prepared for the first time. (2-Methylpyridinium)2[TbCl4(H2O)3]Cl crystallizes monoclinically in the space group P21/n (Z=4) with a=1327.0 pm, b=886.3 pm, c=1911.3 pm and β=105.52°. The coordination polyhedron containing terbium is a pentagonal bipyramid [TbCl4(H2O)3]−. The magnetic behaviour of (2-methylpyridinium)2[TbCl4(H2O)3]Cl and (2-methylpyridinium)3[TbCl6] has been studied. The magnetic data are interpreted by ligand field calculations applying the angular overlap model.

The structure of completely exchanged Tb3+-β′′-Al2O3 (Tb0.46Al10.62Mg0.38O17) crystals has been investigated by single crystal X-ray diffraction methods at room temperature [trigonal, Rm, Z = 3, a = 560.91(8) pm, c = 3330.3(8) pm]. The terbium ions are found to occupy BR (49.2%) and mO positions (50.8%) in nearly the same amount. The structural results are discussed in relation to magnetic measurements on crushed single crystals, where ligand field calculations applying the angular overlap model have been taken into account. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Single crystals of Ln 3 Cl[SiS 4 ] 2 (Ln=La, Ce, Pr) were prepared by the reaction of lanthanide metal, sulfur, silicon and chlorine. Data collection was carried out using a STOE imaging plate detector at 293 K. The homologue compounds crystallize in the space group C2/c of the monoclinic system isotypically to Ln 3 X[SiS 4 ] 2 (X=Br, I) and the A-type of the halide oxosilicates Ln 3 X[SiO 4 ] 2 (X=Cl, Br; Ln=La, Ce, Pr) with four formula units in cells of dimensions: • La 3 Cl[SiS 4 ] 2 : a =1567.2(3) pm, b =777.8(2) pm, c =1101.5(2) pm, β =96.88(2)° • Ce 3 Cl[SiS 4 ] 2 : a =1559.4(3) pm, b =770.2(2) pm, c =1096.9(2) pm, β =97.07(2)° • Pr 3 Cl[SiS 4 ] 2 : a =1555.9(3) pm, b =764.2(1) pm, c =1093.2(2) pm, β =97.40(2)° The corresponding residuals (all data) for the refined structures are 2.28% (La), 2.15% (Ce), and 3.17% (Pr), respectively. In the crystal structures, the chloride ions form chains along [0 0 1] with trigonal coordination by the lanthanide ions.

Einkristalle der Bromid—Thiosilicate Ln3Br[SiS4]2 wurden durch Reaktion von Lanthanidmetall (Ln = La, Ce, Pr, Nd, Sm, Gd), Schwefel, Silicium und elementarem Brom in Quarzglasampullen dargestellt. Die Thiosilicate kristallisieren monoklin in der Raumgruppe C2/c (Z = 4) isotyp zu den Iodid—Analoga Ln3I(SiS4)2 und den Chlorid—Oxosilicaten Ln3Cl[SiO4]2 des A—Typs mit den Gitterkonstanten s. Abstract. In den Kristallstrukturen bilden die Bromid—Ionen Ketten entlang [001] und sind von Lanthanid—Ionen trigonal planar umgeben, wahrend die [SiS4]4-—Baugruppen isolierte verzerrte Tetraeder darstellen. Synthesis and Crystal Structures of Lanthanide Bromide Thiosilicates Ln3Br[SiS4]2 (Ln = La, Ce, Pr, Nd, Sm, Gd) Single crystals of the bromide—thiosilicates Ln3Br[SiS4]2 were prepared by reaction of lanthanide metal (Ln = La, Ce, Pr, Nd, Sm, Gd), sulfur, silicon and bromine in quartz glass tubes. The thiosilicates crystallize in the monoclinic spacegroup C2/c (Z = 4) isotypically to the iodide analogues Ln3I(SiS4)2 and the A—type chloride—oxosilicates Ln3Cl[SiO4]2 with the following lattice constants: La3Br[SiS4]2: a = 1583.3(4) pm, b = 783.0(1) pm, c = 1098.2(3) pm, β = 97.33(3)° Ce3Br[SiS4]2: a = 1570.4(3) pm, b = 776.5(2) pm, c = 1092.2(2) pm, β = 97.28(2)° Pr3Br[SiS4]2: a = 1562.6(3) pm, b = 770.1(2) pm, c = 1088.9(2) pm, β = 97.50(2)° Nd3Br[SiS4]2: a = 1561.4(4) pm, b = 766.0(1) pm, c = 1085.3(2) pm, β = 97.66(3)° Sm3Br[SiS4]2: a = 1555.4(3) pm, b = 758.5(2) pm, c = 1079.9(2) pm, β = 98.28(2)° Gd3Br[SiS4]2: a = 1556.5(3) pm, b = 750.8(1) pm, c = 1074.5(2) pm, β = 99.26(2)° In the crystal structures the bromide ions form chains along [001] with trigonal planar coordination by lanthanide cations, while the [SiS4]4-—building units display isolated distorted tetrahedra.

We deal with the computational determination of the electronic structure and properties of lanthanide ions in complexes and extended structures having open-shell f and d configurations. Particularly, we present conceptual and methodological issues based on Density Functional Theory (DFT) enabling the reliable calculation and description of the f → d transitions in lanthanide doped phosphors. We consider here the optical properties of the Pr3+ ion embedded into various solid state fluoride host lattices, for the prospection and understanding of the so-called quantum cutting process, being important in the further quest of warm-white light source in light emitting diodes (LED). We use the conceptual formulation of the revisited ligand field (LF) theory, fully compatibilized with the quantum chemistry tools: LFDFT. We present methodological advances for the calculations of the Slater–Condon parameters, the ligand field interaction and the spin–orbit coupling constants, important in the non-empirical parameterization of the effective Hamiltonian adjusted from the ligand field theory. The model shows simple procedure using less sophisticated computational tools, which is intended to contribute to the design of modern phosphors and to help to complement the understanding of the 4fn → 4fn−15d1 transitions in any lanthanide system. Swiss National Science Foundation Swiss State Secretariat for Innovation and Research UEFISCDI Romania research grant/PCE 14/2013

Considering the DySc2N@C80 system as a prototype for Single Ion Magnets (SIMs) based on endohedral fullerenes, we present methodological advances and state-of-the art computations analysing the electronic structure and its relationship with the magnetic properties due to the Dy(III) ion. The results of the quantum chemical calculations are quantitatively decrypted in the framework of ligand field (LF) theory, extracting the full parametric sets and interpreting in heuristic key the outcome. An important result is the characterization of the magnetic anisotropy in the ground and excited states, drawing the polar maps of the state-specific magnetization functions that offer a clear visual image of the easy axes and account for the pattern of response to perturbations by the magnetic field applied from different space directions. The state-specific magnetization functions are derivatives with respect to the magnetic field, taken for a given eigenvalue of the computed spectrum. The methodology is based on the exploitation of the data from the black box of the ab initio spin–orbit (SO) calculations. The ground state is characterized by the Jz = ±15/2 quantum numbers with easy axis along the Dy–N bond. The implemented dependence on the magnetic field allowed the first-principles simulation of the magnetic properties. The computational approach to the properties of endohedral fullerenes is an important goal, helping to complement the scarcity of the experimental data on such systems, determined by the limited amount of samples.

We discuss the applicability of the Angular Overlap Model (AOM) to evaluate the electronic structure of lanthanide compounds, which are currently the subject of incredible interest in the field of luminescent materials. The functioning of phosphors is well established by the f–d transitions, which requires the investigation of both the ground 4fn and excited 4fn−15d1 electron configurations of the lanthanides. The computational approach to the problem is based on the effective Hamiltonian adjusted from ligand field theory, but not restricted to it. The AOM parameterization implies the chemical bonding concept. Focusing our interest on this interaction, we take the advantages offered by modern computational tools to extract AOM parameters, which ensure the transparency of the theoretical determination and convey chemical intuitiveness of the non-empirical results. The given model contributes to the understanding of lanthanides in modern phosphors with high or low site symmetry and presents a non-empirical approach using a less sophisticated computational procedure for the rather complex problem of the ligand field of both 4f and 5d open shells. Swiss National Science Foundation Swiss State Secretariat for Innovation and Research

The new ternary compounds UP2S6 (I), UP2S7 (II), U(P2S6)2 (III), and U3(PS4)4 (IV) are prepared from polysulfide fluxes (evacuated quartz tube, 1.

Black crystals of Nd 3 Ti 3 O 8 Se 2 have been synthesized by the reaction of neodymium sesquioxide and titanium sesquiselenide (Nd 2 O 3 :Ti 2 Se 3 =1:1) with a small amount of iodine at 1000°C. The compound crystallizes in the monoclinic space group P2 i /m (Z=2) with the cell parameters a=982.69(17) pm, b=391.78(4) pm, c=1349.9(2) pm, β=111.370(19)°.

Die komplexen Chloride (3-Methylpyridinium)3[DyCl6] (1) und (3-Methylpyridinium)2[DyCl5(Ethanol)] (2) wurden erstmals dargestellt und die Kristallstrukturen anhand von rontgenographischen Einkristalldaten ermittelt. 1 kristallisiert trigonal in der Raumgruppe R3c (Z = 36) mit a = 2953,3(3) pm, b = 2953,3(3) pm und c = 3252,5(4) pm, 2 triklin in der Raumgruppe P1 (Z = 2) mit a = 704,03(8) pm, b = 808,10(8) pm, c = 1937,0(2) pm und α = 77,94(1)°, β = 87,54(1)° sowie γ = 83,26(1)°. Die Strukturen enthalten die oktaedrischen Baueinheiten [DyCl6]3– bzw. [DyCl5(Ethanol)]2–. Preparation and Structure of (3-Methylpyridinium)3[DyCl6] and (3-Methylpyridinium)2[DyCl5(Ethanol)] The complex chlorides (3-Methylpyridinium)3[DyCl6] (1) and (3-Methylpyridinium)2[DyCl5(Ethanol)] (2) have been prepared for the first time. The crystal structures have been determined from single crystal X-ray diffraction data. 1 crystallizes in the trigonal space group R3c (Z = 36) with a = 2953.3(3) pm, b = 2953.3(3) pm and c = 3252.5(4) pm, compound 2 crystallizes in the triclinic space group P1 (Z = 2) with a = 704.03(8) pm, b = 808.10(8) pm, c = 1937.0(2) pm, α = 77.94(1)°, β = 87.54(1)° and γ = 83.26(1)°. The structures contain isolated octahedral building units [DyCl6]3– and [DyCl5(Ethanol)]2–, respectively.

Die komplexen Chloride (2-Methylpyridinium)3[TbCl6] (1) und (2-Methylpyridinium)2[TbCl5(1-Butanol)] (2) wurden erstmals dargestellt und die Kristallstrukturen anhand von rontgenographischen Einkristalldaten bestimmt. 1 kristallisiert monoklin in der Raumgruppe C2/c (Z = 8) mit a = 3241,2(5) pm, b = 897,41(9) pm, c = 1774,2(2) pm und β = 97,83(2)°, 2 monoklin in der Raumgruppe P21/n (Z = 4) mit a = 1372,96(16) pm, b = 997,57(9) pm, c = 1820,5(2) pm und β = 108,75(1)°. Die Strukturen enthalten oktaedrische Baueinheiten der Zusammensetzung [TbCl6]3– bzw. [TbCl5(1-Butanol)]2–. Preparation and Structure of (2-Methylpyridinium)3[TbCl6] and (2-Methylpyridinium)2[TbCl5(1-Butanol)] The complex chlorides (2-Methylpyridinium)3[TbCl6] (1) and (2-Methylpyridinium)2[TbCl5(1-Butanol)] (2) have been prepared for the first time. The crystal structures have been determinated from single crystal X-ray diffraction data. 1 crystallizes in the monoclinic space group C2/c (Z = 8) with a = 3241,2(5) pm, b = 897,41(9) pm, c = 1774,2(2) pm and β = 97,83(2)°, 2 in the monoclinic space group P21/n (Z = 4) with a = 1372,96(16) pm, b = 997,57(9) pm, c = 1820,5(2) pm and β = 108,75(1)°. The structures contain isolated octahedral building units [TbCl6]3– and [TbCl5(1-Butanol)]2–, respectively.