Das Chloridnitrat PrCl2(NO3) · 5 H2O mit kationischen und anionischen Komplexen gemäß [PrCl2(H2O)6][PrCl2(NO3)2(H2O)4]

The Chloride Nitrate PrCl₂(NO₃) · 5 H₂O with Cationic and Anionic Complexes according to [PrCl₂(H₂O)₆][PrCl₂(NO₃)₂(H₂O)₄] Green single crystals of PrCl₂(NO₃) · 5 H₂O have been obtained from an aqueous solution of PrCl₃ and Pr(NO₃)₃. The crystal structure [monoclinic, P2/c, Z = 4, a = 1228.8(3), b = 648.4(1), c = 1266.0(4) pm, β = 91.91(3)°] contains cationic and anionic Pr³⁺ complexes according to [PrCl₂(H₂O)₆][PrCl₂(NO₃)₂(H₂O)₄]. Both nitrate groups of the anionic complex act as bidentate chelating ligands. Hydrogen bonds are observed with water molecules as donors and chlorine as well as oxygen atoms as acceptors.     

Synthese,Kristallstruktur und Magnetismus von [(CH3)2NH2][PrCl4(H2O)2]

Preparation, Crystal Structure, and Magnetism of [(CH₃)₂NH₂][PrCl₄(H₂O)₂] The complex water containing chloride [(CH₃)₂NH₂][PrCl₄(H₂O)₂] has been prepared for the first time and the crystal structure has been determined from single crystal X‐ray diffraction data. The compound crystallizes orthorhombically in the space group Cmca (Z = 8) with a = 1796.6(2) pm, b = 940.7(1) pm, and c = 1238.4(2) pm. The anionic part of the structure is built up by chains of edge‐connected trigondodecahedra [PrCl₆(H₂O)₂]^3– according to [PrCl_4/2Cl₂(H₂O)₂]^–, which are held together by dimethylammonium cations ([(CH₃)₂NH₂]⁺). In order to study the interactions between the praseodymium cation (Pr³⁺) and the ligands magnetic measurements were carried out. The magnetic data were interpreted by ligand field calculations applying the angular overlap model.     

Ce2[SeO3]3 and Pr2[SeO3]3: Non‐Isostructural Oxoselenates(IV) of the Light Lanthanoids

The crystal structures of Ce₂[SeO₃]₃ and Pr₂[SeO₃]₃ have been refined from X‐ray single‐crystal diffraction data. The compounds were obtained using stoichiometric mixtures of CeO₂, SeO₂, Ce, and CeCl₃ (molar ratio 3:3:1:1) or Pr₆O₁₁, SeO₂, Pr, and PrCl₃ (molar ratio 3:27:1:2) heated in evacuated sealed silica tubes at 830 °C for one week. Ce₂[SeO₃]₃ crystallizes orthorhombically (space group: Pnma), with four formula units per unit cell of the dimensions a = 839.23(5) pm, b = 1421.12(9) pm, and c = 704.58(4) pm. Its structure contains only a single crystallographically unique Ce³⁺ cation in tenfold coordination with oxygen atoms arranged as single‐face bicapped square antiprism and two different trigonal pyramidal [SeO₃]^2? groups. The connectivity among the [CeO₁₀] polyhedra results in infinite sheets of face‐ and edge‐sharing units propagating normal to [001]. Pr₂[SeO₃]₃ is monoclinic (space group: P2₁/n) with twelve formula units per unit cell of the dimensions a = 1683.76(9) pm, b = 705.38(4) pm, c = 2167.19(12) pm, and β = 102.063(7)°. Its structure exhibits six crystallographically distinct Pr³⁺ cations in nine‐ and tenfold coordination with oxygen atoms forming distorted capped square antiprisms or prisms (CN = 9), bicapped square antiprisms and tetracapped trigonal prisms (CN = 10), respectively. The [PrO₉] and [PrO₁₀] polyhedra form double layers parallel to (111) by edge‐ or face‐sharing, which are linked by nine different [SeO₃]^2? groups to build up a three‐dimensional framework. In both compounds, the discrete [SeO₃]^2? anions (d(Se⁴⁺–O^2?) = 166–174 pm) show the typical Ψ¹‐tetrahedral shape owing to the non‐bonding “lone‐pair” electrons at the central selenium(IV) particles. Moreover, their stereochemical “lone‐pair” activity seems to flock together in large empty channels running along [010] in the orthorhombic Ce₂[SeO₃]₃ and along [101] in the monoclinic Pr₂[SeO₃]₃ structure, respectively.     

Synthesis and optical properties of Gd2O3:Pr3+ phosphor particles

Spherical-shaped Gd₂O₃:Pr³⁺ phosphor particles were prepared with different concentrations of Pr³⁺ using the urea homogeneous precipitation method. The resulting Gd₂O₃:Pr³⁺ phosphor particles were characterized by X-ray diffraction, field emission scanning electron microscope, and photoluminescence spectroscopy. The effects of the Pr³⁺ doping concentration on the luminescent properties of Gd₂O₃:Pr³⁺ phosphors were investigated. Photoluminescence measurements revealed the Gd₂O₃:1?% Pr³⁺ phosphor particles to have the strongest emission. The luminescence properties of Gd₂O₃:Pr³⁺ particles are strongly affected by the phosphor crystallinity and X-ray diffraction measurements confirmed that the crystallinity of Gd₂O₃ cubic structure could be enhanced by increasing the firing temperature. The luminescent Gd₂O₃:Pr³⁺ phosphor particles have potential applications in areas, such as optical display systems, lamps and etc.     

Pr4S3[Si2O7] und Pr3Cl3[Si2O7]: Durch weiche Fremdanionen modifizierte Derivate von Praseodymdisilicat

Pr₄S₃[Si₂O₇] and Pr₃Cl₃[Si₂O₇]: Derivatives of Praseodymium Disilicate Modified by Soft Foreign Anions For synthesizing both the disilicate derivatives Pr₄S₃[Si₂O₇] and Pr₃Cl₃[Si₂O₇], Pr, Pr₆O₁₁ and SiO₂ are brought to reaction with S and PrCl₃, respectively, in suitable molar ratios (850 °C, 7 d) in evacuated silica tubes. By using NaCl as a flux, Pr₄S₃[Si₂O₇] crystallizes as pale green, transparent single crystals (tetragonal, I4₁/amd, a = 1201.6(1), c = 1412.0(2) pm, Z = 8) with the appearance of slightly compressed octahedra. On the other hand, Pr₃Cl₃[Si₂O₇] emerges as pale green, transparent platelets and crystallizes monoclinically (space group: P2₁, a = 530.96(6), b = 1200.2(1), c = 783.11(8) pm, β = 109.07(1)°, Z = 2). In both crystal structures ecliptically conformed [Si₂O₇]^6– units of two corner‐linked [SiO₄] tetrahedra with Si–O–Si bridging angles of 131° in the sulfide and 148° in the chloride disilicate are present. In Pr₄S₃[Si₂O₇] both crystallographically independent Pr³⁺ cations show coordination numbers of 8 + 1 (5 S^2– and 3 + 1 O^2–) and 9 (3 S^2– and 6 O^2–). For Pr1, Pr2 and Pr3 in Pr₃Cl₃[Si₂O₇] coordination numbers of 10 (5 Cl^– and 5 O^2–) and 9 (2 ×; 4 Cl^– and 5 O^2– or 3 Cl^– and 6 O^2–, respectively) occur.     

The enthalpies of formation of praseodymium halides PrCl3, PrBr3, and PrI3 in the crystalline state and aqueous solution

The enthalpies of solution of praseodymium tribromide and triiodide in water were measured at 298.15 K in a hermetic isothermic-shell swinging calorimeter. The data obtained and the Δ_f H° (Pr³⁺, sln, ∞H₂O, 298 K) value found earlier were used to calculate the enthalpies of formation of three praseodymium halides (PrCl₃, PrBr₃, and PrI₃) in the crystalline state and aqueous solution.     

Strukturchemische und impedanzspektroskopische Untersuchungen an Mg2+-stabilisierten Na+/Pr3+-β″-Al2O3-Kristallen

Structural Chemistry and Impedance Spectroscopy of Mg²⁺ stabilized Na⁺/Pr³⁺-β″-Aluminas The structure with the ionic distribution in the conduction planes of a Pr³⁺-exchanged Mg²⁺ stabilized Na⁺-β″-alumina crystal, composition determined by electron microprobe analysis to Na_1.19Pr_0.13Mg_0.49Al_10.49O₁₇ (degree of exchange ξ = 25%, related to Na⁺ content), has been investigated by single crystal X-ray diffraction methods at room temperature (R3 m, Z = 3, a = 561.8(2) pm, c = 3 361.5(11) pm). Pr³⁺ is slightly shifted in the ab-plane from the centrosymmetric 9 d (mO) into a 18 h site. Na⁺ occupies 18 h as well as 6 c (BR) positions. Ionic conductivity data of Mg²⁺ stabilized Na⁺/Pr³⁺-β″-Al₂O₃ crystals with varying degree of exchange determined by impedance spectroscopy are given in an Arrhenius diagram. With growing Pr³⁺ content the conductivity σ decreases with increasing activation energy.     

Nitridsulfidchloride der Lanthanide: III. Synthese und Kristallstruktur von Pr5N3S2Cl2

Nitride Sulfide Chlorides of the Lanthanides. III. Synthesis and Crystal Structure of Pr₅N₃S₂Cl₂ By reacting praseodymium with sulfur, sodium azide and praseodymium trichloride in sealed, evacuated silica tubes (850°C, 7 d), the nitride sulfide chloride Pr₅N₃S₂Cl₂ is obtained in case of a 4:2:1:1 molar ratio of the reactants (Pr:S:NaN₃:PrCl₃). A slight excess of trichloride or the addition of NaCl as a flux supports the yield of brownish red, rod-shaped transparent crystals which prove to be stable against hydrolysis. The crystal structure (monoclinic, C2/m (no. 12), a = 1540.2(1), b = 400.92(3), c = 1656.3(1) pm, β = 101.24(1)°, Z = 4, R = 0.039, R_w = 0.028) was determined by means of X-ray single crystal data. Thus five crystallographically different cations (Pr³⁺) are present which with three distinct kinds of nitride anions (N^3?) build up two types of translationally commensurate chains from interconnected [NPr₄] tetrahedra. With an additional edge per “chain-link” in chain I, two single chains [NPr_3/3^ePr_1/1^t]³⁺ (?[NPr₂]³⁺) of cis-edge connected [NPr₄] tetrahedra (known from the Sm₄N₂S₃-type structure) are condensed into the double chain [(N1){(Pr1)_(2+2)/(2+2)^e,e(Pr2)_(2+1)/(2+1)^e,v}(N2)(Pr3)_1/1^t]³⁺ (?[N₂Pr₃]³⁺). Chain II consists of two single chains [NPr_2/2^vPr_2/1^t] ⁶⁺ (?[NPr₃]⁶⁺) of vertex-connected [NPr₄] tetrahedra (known from the Sm₃NS₃-type structure), which are condensed to the double chain [(N3)(Pr4)_2/2^e(Pr5)_2/2^v]³⁺ (?[NPr₂]³⁺) via an additional edge per “chain-link” too. Both types of chains are bundled along [010] like a closest packing of rods. Four crystallographically different but by X-ray diffraction indistinguishable anions S^2? and Cl^? hold both cationic double chains together and also adjust the charge balance in a molar ratio of 1 : 1.     

Growth and spectroscopic properties of the Pr3+ ions in the LiPrP4O12 single crystals

LiPrP₄O₁₂ single crystals are synthetized and studied by both, optical absorption and emission spectroscopy. The processes leading to the depopulation of the ³P₀ and ¹D₂ excited states of Pr³⁺ are analyzed on the basis of experimental data and the Judd-Ofelt theory. From the analysis of the fluorescence spectra of Pr³⁺ ions two unequivalent positions in LiPrP₄O₁₂ crystal were concluded.     

Pr8Cl7B7: preparation, structure, bonding, properties

Pr₈Cl₇B₇ is prepared from stoichiometric mixtures of PrCl₃3, Pr and B at 1220 K in closed Ta capsules. Pr₈Cl₇B₇ forms golden coloured needles sensitive to moist air. It crystallizes in the space group P1 with a = 773.1(2) pm, b = 903.0(2) pm, c = 1419.4(3) pm, a = 81.55(3)°, β = 82.18(3)°, and γ = 64.76(3)°. In the crystal structure Pr₆ trigonal prisms are condensed to double chains which run parallel [100]. Some of the prisms and rectangular prism faces are centered by boron atoms which leads to B₃, B₆, B₈ rings, and B₂ dumbbells condensed into ribbons. These Pr₈B₇ strands are surrounded and held together by the Cl atoms. Pr₈Cl₇B₇ is a metallic conductor and shows Curie Weiss behavior with μ_eff = 3.48 μ_B. According to extended Hückel calculations, the distribution of valence electrons is best described by a formulation Pr₈¹⁸⁺Cl₇⁷⁻B₇¹¹⁻. Bonding within the boron ribbons is thus nearly optimal, while the average 4f² 5d^3/4 configuration of Pr accounts for both the observed magnetic moment and metallic conductivity.     

Research on Molecular Structure and Electronic Properties of Ln3+ (Ce3+, Tb3+, Pr3+)/Li+ and Eu2+ Co-Doped Sr2Si5N8 via DFT Calculation

We use density functional theory (DFT) to study the molecular structure and electronic band structure of Sr₂Si₅N₈:Eu²⁺ doped with trivalent lanthanides (Ln³⁺ = Ce³⁺, Tb³⁺, Pr³⁺). Li⁺ was used as a charge compensator for the charge imbalance caused by the partial replacement of Sr²⁺ by Ln³⁺. The doping of Ln lanthanide atom causes the structure of Sr₂Si₅N₈ lattice to shrink due to the smaller atomic radius of Ln³⁺ and Li⁺ compared to Sr²⁺. The doped structure’s formation energy indicates that the formation energy of Li⁺, which is used to compensate for the charge imbalance, is the lowest when the Sr2 site is doped. Thus, a suitable Li⁺ doping site for double-doped lanthanide ions can be provided. In Sr₂Si₅N₈:Eu²⁺, the doped Ce³⁺ can occupy partly the site of Sr₁²⁺ ([SrN₈]), while Eu²⁺ accounts for Sr₁²⁺ and Sr₂²⁺ ([SrN₁₀]). When the Pr³⁺ ion is selected as the dopant in Sr₂Si₅N₈:Eu²⁺, Pr³⁺ and Eu²⁺ would replace Sr₂²⁺ simultaneously. In this theoretical model, the replacement of Sr²⁺ by Tb³⁺ cannot exist reasonably. For the electronic structure, the energy level of Sr₂Si₅N₈:Eu²⁺/Li⁺ doped with Ce³⁺ and Pr³⁺ appears at the bottom of the conduction band or in the forbidden band, which reduces the energy bandgap of Sr₂Si₅N₈. We use DFT+U to adjust the lanthanide ion 4f energy level. The adjusted 4f-CBM of Ce_Sr1Li_Sr1-Sr₂Si₅N₈ is from 2.42 to 2.85 eV. The energy range of 4f-CBM in Pr_Sr1Li_Sr1-Sr₂Si₅N₈ is 2.75–2.99 eV and its peak is 2.90 eV; the addition of Ce³⁺ in Eu_Sr1Ce_Sr1Li_Sr1 made the 4f energy level of Eu²⁺ blue shift. The addition of Pr³⁺ in Eu_Sr2Pr_Sr2Li_Sr1 makes part of the Eu²⁺ 4f energy level blue shift. Eu²⁺ 4f energy level in Eu_Sr2Ce_Sr1Li_Sr1 is not in the forbidden band, so Eu²⁺ is not used as the emission center.     

Synthesis and Crystal Structure of the Novel Compound Mg4.5Pr79.5Mo126O312 Containing Mo3, Mo7 and Mo19 Clusters

The synthesis and crystal structure of the novel reduced molybdenum oxide Mg_4.5Pr_79.5Mo₁₂₆O₃₁₂ are presented. This compound crystallizes in the trigonal space group R-3 m with a = 11.3061(2) Å, c = 58.242(1) Å, V = 6447.5(2) Å³, and Z = 1. Refinements yield R(F ²) = 0.0433 and wR(F ²) = 0.0931 for 2827 unique reflections. The structure is built up from alternating slabs made up of molybdenum forming Mo₃, Mo₇ and Mo₁₉ clusters, praseodymium and oxygen atoms, and slabs containing isolated MoO₆ octahedra. The Pr³⁺ cations are localized either within the slabs or at their borderlines to ensure the cohesion between the slabs. Of the six crystallographically independent sites occupy by the Pr³⁺ cations, two of them also contain randomly about 15% and 20% of Mg²⁺ cations while the remaining four are fully occupied by the Pr³⁺ cations.     

Preparation,characterization and luminescent properties of spherical CaTiO3:Pr3+ phosphors by spray pyrolysis

In this paper, spherical Pr³⁺-doped CaTiO₃ phosphor particles were fabricated through a two-step spray pyrolysis process, using citric acid and polyethylene glycol (PEG) as additives. X-ray diffraction (XRD), scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), thermogravimetric and differential thermal analysis (TG–DTA), X-ray photoelectron spectra (XPS), photoluminescence (PL), cathodoluminescence (CL) spectroscopy, and lifetime measurements were employed to characterize these samples. The results reveal that the as-prepared CaTiO₃:Pr³⁺ phosphors are spherical with submicron particle size. The particles show a strong red emission corresponding to ¹D₂–³H₄ (612 nm) of Pr³⁺ under the ultraviolet excitation (325 nm) and low voltage electron beams (1–5 kV). Furthermore, the morphology, PL and CL intensities of the CaTiO₃:Pr³⁺ phosphors can be tuned by altering the concentration of PEG, annealing temperature, and acceleration voltage. These phosphors show potential applications in the field of field emission displays (FEDs).     

Zur Kenntnis von Tripraseodym‐hexanitridotriborat Pr3B3N6: Neue Synthese und Verfeinerung der Kristallstruktur

On Tripraseodymium Hexanitridotriborate Pr₃B₃N₆: New Synthesis and Crystal Structure Refinement Single‐crystalline Pr₃B₃N₆ was obtained by the reaction of praseodymium and BN_x(NH)_y(NH₂)_z in a NaCl melt under N₂ atmosphere in a high‐frequency furnace at 1250 °C. Contrary to literature data, Pr₃B₃N₆ crystallizes in the centrosymmetric space group R 3 c as revealed by single‐crystal X‐ray diffraction (a = 1211.95(9), c = 701.53(7) pm, Z = 6, R1 = 0.0258, wR2 = 0.0658). In the solid, Pr₃B₃N₆ contains Pr³⁺ and planar cyclotrinitridoborate units B₃N₆^9–. The anions represent motifs from the structure of hexagonal boron nitride (h‐BN) and they are stacked analogously along [001]. Both the bond lengths B–N (average value 147.8 pm) and the interionic distances between the anions (350.8 pm) are comparable with the values in h‐BN.     

Progress of estuarine research in China over last 50 years

Under 216 nm UV-excitation, cascade emission of Pr³⁺ occurs from¹S₀ state in LaBaB₉O₁₆:Pr³⁺ that converts a single UV photon of high energy into two visible photons. The observation of the cascade emission in this oxide matrix is largely due to the weak crystal field on the lanthanum sites. The analysis of the vibrational coupling indicates that the radiative transition from the³ P ₀ state is related to the low phonon frequency of the BO₄ borate groups bonded to the lanthanum atoms(hω _max∼850 cm^-1). On the other hand, the cascade emission does not take place in a closely related material, YBaB₉O₁₆:Pr³⁺, which can be interpreted by the fact that the 4f5d levels are located below the¹S₀ level in this material.     

Progress of estuarine research in China over last 50 years

Under 216 nm UV-excitation, cascade emission of Pr³⁺ occurs from¹S₀ state in LaBaB₉O₁₆:Pr³⁺ that converts a single UV photon of high energy into two visible photons. The observation of the cascade emission in this oxide matrix is largely due to the weak crystal field on the lanthanum sites. The analysis of the vibrational coupling indicates that the radiative transition from the³ P ₀ state is related to the low phonon frequency of the BO₄ borate groups bonded to the lanthanum atoms(hω _max～850 cm^-1). On the other hand, the cascade emission does not take place in a closely related material, YBaB₉O₁₆:Pr³⁺, which can be interpreted by the fact that the 4f5d levels are located below the¹S₀ level in this material.     

Systematic study of photoluminescence upon band gap excitation in perovskite-type titanates R1/2Na1/2TiO3:Pr (R=La, Gd, Lu, and Y)

Pr³⁺-doped perovskites R_1/2Na_1/2TiO₃:Pr (R=La, Gd, Lu, and Y) were synthesized, and their structures, optical absorption and luminescent properties were investigated, and the relationship between structures and optical properties are discussed. Optical band gap of R_1/2Na_1/2TiO₃ increases in the order R=La, Gd, Y, and Lu, which is primarily due to a decrease in band width accompanied by a decrease in Ti-O-Ti bond angle. Intense red emission assigned to f-f transition of Pr³⁺ from the excited ¹D₂ level to the ground ³H₄ state upon the band gap photo-excitation (UV) was observed for all compounds. The wavelength of emission peaks was red-shifted in the order R=La, Gd, Y, and Lu, which originates from the increase in crystal field splitting of Pr³⁺. This is attributed to the decrease in inter-atomic distances of Pr-O together with the inter-atomic distances (R, Na)-O, i.e., increase in covalency between Pr and O. The results indicate that the luminescent properties in R_1/2Na_1/2TiO₃:Pr are governed by the relative energy level between the ground and excited state of 4f² for Pr³⁺, and the conduction and valence band, which is primarily dependent on the structure, e.g., the tilt of TiO₆ octahedra and the Pr-Ti inter-atomic distance and the site symmetry of Pr ion.     

Synthesis and luminescent properties of LaInO3: RE3+ (RE = Sm,Pr and Tb) nanocrystalline phosphors for field emission displays

LaInO₃: Sm³⁺, LaInO₃: Pr³⁺ and LaInO₃: Tb³⁺ phosphors were prepared through a Pechini-type sol–gel process. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD results reveal that the pure LaInO₃ phase can also be obtained at 700 °C. FE-SEM images indicate that the LaInO₃: Sm³⁺, LaInO₃: Pr³⁺ and LaInO₃: Tb³⁺ phosphors are composed of aggregated spherical particles with sizes around 80–120 nm. Under the excitation of ultraviolet light and low voltage electron beams (1–5 kV), the LaInO₃: Sm³⁺, LaInO₃: Pr³⁺ and LaInO₃: Tb³⁺ phosphors show the characteristic emissions of Sm³⁺ (⁴G_5/2–⁶H_5/2,7/2,9/2 transitions, yellow), Pr³⁺ (³P₀–³H₄, ³P₁–³H₅, ¹D₂–³H₄ and ³P₀–³F₂ transitions, blue–green) and Tb³⁺ (⁵D₄–⁷F_6,5,4,3 transitions, green) respectively. The corresponding luminescence mechanisms are discussed. These phosphors have potential applications in field emission displays.     

Phosphaniminato-Komplexe von Niob und Tantal. Die Kristallstrukturen von [NbCl4(NPiPr3)(CH3CN)], [NbCl3(NPiPr3)2], [TaCl4(NPiPr3)]2 und [TaCl3(NPiPr3)2]

Phosphorane Iminato Complexes of Niobium and Tantalum. Crystal Structures of [NbCl₄(NPⁱPr₃)(CH₃CN)], [NbCl₃(NPⁱPr₃)₂], [TaCl₄(NPⁱPr₃)]₂, and [TaCl₃(NPⁱPr₃)₂] The title compounds have been prepared from the pentachlorides of niobium and tantalum with the silylated phosphorane imine Me₃SiNPⁱPr₃. They are characterized by IR spectroscopy and crystal structure determinations. NbCl₄(NPⁱPr₃)(CH₃CN)] . Space group Pna2₁, Z = 4, 2102 observed unique reflections, R = 0.022. Lattice dimensions at ?50°C: a = 1627.2, b = 876.3, c = 1335.3 pm. The compound forms monomeric molecules with the acetonitrile molecule in trans position to the phosphorane iminato group. This group shows a short NbN distance of 178.2 pm with a NbNP bond angle of 165.2°. [NbCl₃(NPⁱPr₃)₂] . Space group Cc, Z = 4, 2534 observed unique reflections, R = 0.046. Lattice dimensions at 20°C: a = 1302.65, b = 1321.69, c = 1672.04 pm, β = 111.713°. The compound forms monomeric molecules with a distorted bipyramidal surrounding of the niobium atom and equatorially arranged phosphorane iminato groups. [TaCl₄(NPⁱPr₃)]₂ . Space group Pbca, Z = 4, 1537 observed unique reflections, R = 0.037. Lattice dimensions at ?40°C: a = 1420.6, b = 1483.9, c = 1622.0 pm. The compound forms centrosymmetric dimeric molecules with dissimilarly long Ta₂Cl₂ bridges and equatorially arranged phosphorane iminato groups. [TaCl₃(NPⁱPr₃)₂] . Space group Cc, Z = 4, 5737 observed unique reflections, R = 0.039. Lattice dimensions at ?50°C: a = 1303.9, b = 1327.2, c = 1682.1 pm, β = 111,92°. The compound is isotypical with the corresponding niobium compound.     

Crystal growth and structural motifs of luminescent PrCl3·ROH complexes: Molecular adducts and 1-D chains of tetradecanuclear rings

Pr₂Cl₆(CH₃OH)₈ (1), Pr₂Cl₆((CH₃)₂CHOH)₈ (2) and (PrCl₃)₇(CH₃CH₂CH₂OH)₁₈·(CH₃CH₂CH₂OH) (3) were synthesized via slow evaporation of a supersaturated solution of PrCl₃ in methanol, isopropanol and n-propanol respectively. The crystal structures were determined, revealing two very different topological arrangements. The evaporation in the presence of methanol and isopropanol lead to dimeric molecular adducts, while n-propanol leads to the formation of 1-D chains of tetradecanuclear rings. The molecular adducts are held together via edge sharing polyhedra while the rings are held together via edge- and face-sharing polyhedra. The absorbance and luminescence of these compounds was also investigated.