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Cluster compounds containing the [(W6I8)(CH3CN)6]4+ ion were established. Photophysical properties of [(W6I8)(CH3CN)6](BF4)4 are compared to those of compounds featuring the [(W6I8)L6]2− ion.

Y4O2(CN2)3Cl2 and some isotypic rare earth (RE) carbodiimides RE4O2(CN2)3Cl2 (RE = Sm, Gd, Tb) were prepared by solid-state metathesis reaction between RECl3, REOCl and Li2CN2. The crystal structure of Y4O2(CN2)3Cl2 was solved and refined from single-crystal XRD data with the monocline space group C2/m. Homologous compounds with RE = Sm, Gd were assigned isotopically by means of XRD powder diffraction. The structure of Y4O2(CN2)3Cl2 is characterized by one-dimensional cluster chains which are showing a striking resemblance to the trans-edge bridging RE6-octahedra in the structures of Y2Cl3, β-Y2Cl3N, and RE2N(CN2)Cl, despite different numbers of cluster electrons. Crystals of RE4O2(CN2)3Cl2 appear as transparent rods. The presence of (NCN)2− ions is confirmed by infrared spectroscopy. Y4O2(CN2)3Cl2, doped with Ce3+, is a photoluminescent material showing an emission band in the orange region (λem = 550 nm) of the visible spectrum.

New rare earth (RE) carbodiimides having the formula RE8O(CN2)10Br2 were synthesized by solid-state metathesis reactions. Structure determinations and refinements, based on single-crystal X-ray diffraction data, are performed with the space group P͞3c1. Homologous compounds with RE = La, Ce, Pr, and Nd are assigned isotypically. The refined crystal structure appears most unusual for rare earth carbodiimide compounds. The structure is characterized by the formally neutral [RE6O(NCN)8] fragment that is tightly interconnected by carbodiimide ions into a network structure, and contains additional RE3+ ions in the structure. Crystals of the compounds show characteristic colors of their corresponding RE3+ ions and behave stable in air. The presence of (CN2)2− ions was confirmed by infrared spectroscopy. Ce8O(CN2)10Br2 is a photoluminescent material that is showing a broad and efficient emission band in the yellow region of the visible spectrum.

Thallium(I) decahydro-closo-decaborate Tl2[B10H10] and thallium(I) dodecahydro-closo-dodecaborate Tl2[B12H12] are readily available as microcrystalline powders from reactions of thallium(I) carbonate Tl2[CO3] with aqueous solutions of the respective free acid (H3O)2[B10H10] or (H3O)2[B12H12]. Tl2[B12H12] crystallizes with an anti-fluorite related structure (cubic, F m 3 ‾ $Fm\bar{3}$ , a = 1074.23(8) pm, Z = 4). Each Tl+ cation is coordinated by four icosahedral [B12H12]2– anions (d(B–B) = 180–181 pm) providing a twelvefold coordination sphere of hydrogen atoms (d(Tl–H) = 296 pm). Tl2[B10H10] crystallizes monoclinically in the space group P21/n with a = 704.03(5), b = 1111.45(8), c = 1281.16(9) pm and β = 94.912(3)° for Z = 4. The bicapped square antiprismatic [B10H10]2– anions (d(B–B) = 147–176 pm to the two apical boron atoms, d(B–B) = 161–199 pm within the corpus) again form distorted tetrahedra around the (Tl1)+, but square pyramids around the (Tl2)+ cations. Thus (Tl1)+ is coordinated by 12 hydrogen atoms (d(Tl1–H) = 275–315 pm), but (Tl2)+ only by 11 of them (d(Tl2–H) = 267–357 pm). Both compounds show a greenish-yellow photoluminescence caused by an interconfigurational 6sp –6s 2 emission (3Pn→1S0, n = 0–2) at the Tl+ cation.

Previously unknown thallium(i) chloride hydroborate Tl3Cl[B12H12], crystallising with a hexagonal perovskite-type motif, was obtained by the reaction of the carbonate Tl2[CO3] with an aqueous solution of (H3O)2[B12H12] in the presence of Cl− anions.

We carried out three choice experiments with 6116 nocturnal lepidopteran individuals (95 species, 7 families, 32 075 counts), each replicated 105 times during the seasons of 2 years. Moths were released indoors at the centre of a 10 × 10 m area with different lamps placed at each corner. In experiment 1, lamps emitted ultraviolet (UV) (peak at 365 nm), blue (450 nm), green (520 nm) or cool white (450 and 520 nm) radiation. In experiment 2, UV was replaced by red (640 nm). In experiment 3, we used UV and three mixed radiation lamps of different emission intensities (365–520 nm). We applied a linear mixed effect model to test for differences in attraction to the light sources. Among all counts, 12.2% (males) and 9.2% (females) were attracted to a lamp. Among the lamp counts, 84% were made at the UV lamp in experiment 1. In experiment 2, 63% of the counts were made at the blue lamp. In experiment 3, most counts were made at the strongest mixed radiation lamp (31%), and the UV lamp (28%). Patterns were generally similar across Lepidopteran families, and for both sexes. Moths are clearly preferentially attracted to short-wave radiation. Even small quantities of UV radiation, emitted, for example, by metal halide lamps and certain mercury vapour tubes, will disproportionately contribute to light pollution. Since blue light also attracts moths strongly, lamps with a low proportion of blue light should be given priority in lighting planning. (Less)

The light-induced antibacterial and antifungal properties of A2[M6I8L6] with M = Mo and W, A = organic cation, L = ligand have been studied. The photoactive compounds (TBA)2[W6I8(C7H7SO3)6] and (TBA)2[W6I8(COOCF3)6] have been incorporated into a permeable silicone matrix and were measured for their application in the decomposition of multi-resistant bioactive species (hospital germs) such as S. aureus and P. aeruginosa as well as fungi. In addition, we present a new high volume synthesis route for these types of cluster compounds departing from the soluble compound W6I22.

Photophysical properties of tungsten iodides with the [W6I14]2− cluster core have been described with respect to phosphorescence and phosphorescence quenching by molecular oxygen. This process involves energy transfer from excited triplet states of the cluster onto molecular oxygen. In the present study we investigate deactivation channels of exited triplet states of the [W6I14]2− cluster towards rare earth ions. For this purpose, we synthesized several supramolecular assemblies made of [W6I14]2− clusters and metal cryptates and investigated their crystal structures and photophysical properties. UV/Vis photoexcitation of solid [Crypt-A]-[W6I14] (A = alkaline metal) and [Crypt-RE]-[W6I14] revealed phosphorescence of the cluster, respectively of the photophysically active rare earth metal (RE) center. A cluster to cryptate energy transfer is proven with a photophysically active rare earth ion by the emission of Yb3+ at 977 nm (2F5/2–2F7/2) and Nd3+ 1072 nm (4F3/2–4I11/2). These results show that an effective excitation of near-infrared-emitting rare earth ions is possible under excitation up to 550 nm with [Crypt-RE]-[W6I14] assemblies.

The phase LixCa16−xSi17N32−xO2+x was synthesized by solid-state metathesis at 1050 °C in weld-sealed niobium ampoules. The crystal structure was solved from powder X-ray diffraction data in the space group F3m (a = 14.7391(1) A, Z = 4); it is closely related to the previously reported structure of Ca16Si17N34. The structure of LixCa16−xSi17N32−xO2+x is based on a complex network of [SiN4] tetrahedra with interstitial voids filled by Ca ions, partially substituted by Li. This Li substitution is charge-compensated by replacement of N by O in the structure. Theoretical calculations confirm that the unit cell volume decreases with increasing stoichiometric factor x. Europium doped samples of this compound show intense Eu2+ emission at 536 nm on excitation with near-UV or blue radiation at 350–480 nm. Ce3+ doping yields orange to red emission with two broad emission bands at 600 and 665 nm.

Cerium and chromium co-doped gadolinium aluminum gallium garnets were prepared using sol-gel technique. These compounds potentially can be applied for NIR-LED construction, horticulture and theranostics. Additionally, magnesium and calcium ions were also incorporated into the structure. X-ray diffraction data analysis confirmed the all-cubic symmetry with an Ia-3d space group, which is appropriate for garnet-type materials. From the characterization of the luminescence properties, it was confirmed that both chromium and cerium emissions could be incorporated. Cerium luminescence was detected under 450 nm excitation, while for chromium emission, 270 nm excitation was used. The emission of chromium ions was exceptionally intense, although it was determined that these compounds are doped only by parts per million of Cr3+ ions. Typically, the emission maxima of chromium ions are located around 650–750 nm in garnet systems. However, in this case, the emission maximum for chromium is measured to be around 790 nm, caused by re-absorption of Cr3+ ions. The main observation of this study is that the switchable emission wavelength in a compound of single phase was obtained, despite the fact that doping with Cr ions was performed in ppm level, causing an intense emission in NIR region.

A series of new compounds MI(OCN) were prepared from the mixtures of MI2 and K(OCN) (M = Sr, Eu or Ba) by solid-state reactions that were controlled by differential scanning calorimetry (DSC) and differential thermal analysis (DTA) techniques. The presence of two phases is highlighted for BaI(OCN) which crystallizes in the Pnma (α-BaI(OCN)) and Cmcm (β-BaI(OCN)) space groups. The SrI(OCN), EuI(OCN) and β-BaI(OCN) compounds crystallize in the same orthorhombic Cmcm space group and the structure consists of a layered arrangement of [M2I2]2+ blocks separated by single layers of cyanate ions that are found to be related to the Sillen-type structure. The polymorphism of BaI(OCN) was also observed by analyzing the infrared (IR) spectra. This analysis showed for β-BaI(OCN) splitting bands, which were ascribed to the presence of more than one resonant cyanate form that can be induced by the dynamical disorder of OCN units. In contrast, the α-BaI(OCN) vibration modes suppose the existence of one cyanate form that adopts a defined orientation. The SrI(OCN) and BaI(OCN) compounds were doped with Eu2+. The luminescence spectra recorded under excitation at 340 and 350 nm revealed a blue emission of Eu2+ at 431 nm for the β-BaI(OCN) and SrI(OCN) phases and at 427 nm for the α-BaI(OCN) phase that was ascribed to the 4f65d1→8S7/2 (4f7) transition.

The purpose of this study is to investigate the optical properties of Sm3+ doped K2Bi(PO4)(MoO4) phosphors as possible candidates for application in light emitting diodes (LEDs) for horticultural and general lighting applications. Sm3+ doped phosphors with 0.5%, 1%, 2.5%, 5%, 10%, 25%, 50%, 75% and 100% Sm3+ have been prepared by solid state reaction method. The synthesized materials were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The room temperature (RT) reflection, excitation, and emission spectra, photoluminescence (PL) decay curves, as well as temperature dependent emission and excitation spectra and PL decay curves were measured and discussed. Moreover, quantum efficiencies, and lumen equivalents (LE) were determined and discussed. The prepared K2Bi(PO4)(MoO4):Sm3+ phosphor samples show moderate quantum efficiency, high colour purity, and a high quenching temperature. These properties are required for phosphors if they are under consideration for application in LEDs and other areas. It was also shown, that the PL emission of the phosphor well matches the absorption of the main plant pigments thus making it a good candidate for horticultural lighting applications. Using this phosphor and a near-UV LED a phosphor-converted LED (pcLED) prototype, meeting the photophysiological needs of plants, was designed. Supplementing the prototype with a green or lime LED the colour rendering index and luminous efficacy of radiation of the prototype is greatly increased thus making it more efficient and pleasant for people present at the greenhouse.

Photophysical properties of tungsten iodides with the [W6I14]2- cluster core have been described with respect to phosphorescence and phosphorescence quenching by molecular oxygen. This process involves energy transfer from excited triplet states of the cluster onto molecular oxygen. In the present study we investigate deactivation channels of exited triplet states of the [W6I14]2- cluster towards rare earth ions. For this purpose, we synthesized several supramolecular assemblies made of [W6I14]2- clusters and metal cryptates and investigated their crystal structures and photophysical properties. UV/Vis photoexcitation of solid [Crypt-A]-[W6I14] (A = alkaline metal) and [Crypt-RE]-[W6I14] revealed phosphorescence of the cluster, respectively of the photophysically active rare earth metal (RE) center. A cluster to cryptate energy transfer is proven with a photophysically active rare earth ion by the emission of Yb3+ at 977 nm (2F5/2-2F7/2) and Nd3+ 1072 nm (4F3/2-4I11/2). These results show that an effective excitation of near-infrared-emitting rare earth ions is possible under excitation up to 550 nm with [Crypt-RE]-[W6I14] assemblies.

The light-induced antibacterial and antifungal properties of A

Lemon-yellow single crystals of Eu2[SiO4] were obtained by reaction of elemental europium with Eu2O3 in the presence of SiO2 carried out in evacuated silica ampules at 1373 K for 48 h followed by constant cooling to room temperature with 120 K per hour. Eu2[SiO4] crystallizes at room temperature in the larnite-type structure of β-Ca2[SiO4] (monoclinic, P21/n) with parameters a = 565.02(5), b = 709.15(6), c = 975.84(8) pm, β = 92.614(3)° for Z = 4. At 452 K it undergoes a reversible phase transition to an incommensurate structure similar to the isotypic compounds Sr2[SiO4] and K2[SeO4]. The phase transition energy was determined to 0.54(2) J·g–1 by DSC measurements and temperature dependent birefringence measurements show that the phase transition exhibits a significant hysteresis. Refinements of the structure of Eu2[SiO4] based on single crystal X-ray diffraction data show that the high temperature modification crystallizes in the orthorhombic space group Pnma(α00)0ss with a = 710.16(6), b = 566.93(5), c ...

This work concerns the cathode (CL) and photoluminescence (PL) of silicates according to the compositions K2MSi2O7 (M = Zr, Hf) and SrZrSi2O7. It also relates to the band gap determination of K2ZrSi2O7 and SrZrSi2O7, which were determined to 5.6 eV for the former and 5.0 eV for the latter compound. Modification of K2ZrSi2O7 by the substitution of Zr by Hf shows that the incorporation of 20% Hf improves the PL of the material, while a complete replacement of Zr4+ by Hf4+ entirely quenches the charge-transfer based luminescence process. Quenching of the luminescence is also observed for the incorporation of Ln3+ (Ln = Ce, Pr, Tb). The emission band of K2(Zr,Hf)Si2O7 is nicely located in the UV-C range yielding an overlap with the germicidal activation curve (GAC) close to that of Lu2Si2O7:Pr, i.e. of about 55%. This finding brands the material as an interesting compound for radiation sources to be used in disinfection devices.

This work concerns polycrystalline GdB 5 O 9 :Eu 3+ , which were made as single phase samples by a simple aqueous sol-gel method. The phase formation of the samples was monitored by X-ray diffraction measurements. Excitation of the synthesized phosphors with near-UV radiation resulted in bright red emission with excellent colour saturation. The colour coordinates were relatively stable regardless Eu 3+ concentration and temperature increase. Furthermore, under 394.5 nm excitation quantum efficiency of the phosphors doped with up to 25% Eu 3+ is 100%, what is excellent for practical application. The endmember of the series, EuB 5 O 9 , possessed quantum efficiency of about 64%, which is still high for a compound with such large Eu content. Temperature dependent emission spectra revealed emission intensity decrease upon increasing temperature and that the samples doped with 1%, 50%, and 100% Eu 3+ lose half of their photoluminescence efficiency at 891, 603, and 515 K, respectively. Besides, the unique emission spectra profile makes these luminescent materials very attractive for application in luminescent security pigments.

The mixed-anionic hydride oxide chloride LiEu2HOCl2 with divalent europium was synthesized by the reduction of Eu2O3 with LiH in a LiCl flux at 750 °C for 4 days in silica-jacketed niobium capsules. According to structure determination by single-crystal X-ray diffraction the yellow compound crystallizes in the orthorhombic space group Cmcm (a = 1492.30(11) pm, b = 570.12(4) pm, c = 1143.71(8) pm, Z = 8) with a crystal structure closely related to that one of the quaternary hydride oxide LiLa2HO3 and the hydride nitride LiSr2H2N. On the other hand it can also be derived from the PbFCl-type structure of EuHCl showing astonishingly short Eu2+∙∙∙Eu2+ contacts of 326 and 329 pm. Both crystallographically different Eu2+ cations have nine anionic neighbors, while all other ions (Li+, H-, O2- and Cl-) reside in six-membered coordination spheres. LiEu2OCl2H exhibits a bright yellow luminescence with an emission maximum at 581 nm upon excitation at 440 nm.

Cluster compounds (TBA)2[Mo6I8(CF3SO3)6], (TBA)2[W6I8(CF3SO3)6], and (TBA)2[W6Br8(CF3SO3)6] are prepared and structurally characterized from single-crystal X-ray diffraction data. All compounds show red emission on photoexcitation at 400 nm. However, the phosphorescence of crystalline samples is quenched in the presence of oxygen, depending on the partial pressure of oxygen. The distinct phosphorescence-quenching behavior of compounds containing trifluoromethanesulfonato (CF3SO3–) ligands is compared with corresponding compounds with trifluoroacetato (CF3COO–) and p-toluolsulfonato (CH3C6H4SO3–) ligands. By studying these compounds, we investigate the relationship of more- or less-electron-withdrawing ligands (L) of (TBA)2[M6X8L6] halide (X) clusters, their redox potentials (E0), and their phosphorescence-quenching behavior under variable oxygen partial pressures.

This work concerns the synthesis, effect of fluxes on the formation of single phase materials, and spectroscopic characterization of rare earth pyrosilicates according to Ln 2 Si 2 O 7 (with Ln = La, Lu, Y). It turned out that by the support of LiF as a flux it is possible to obtain a single phase of the polymorph Lu 2 Si 2 O 7 , La 2 Si 2 O 7 , and Y 1,9 La 0,1 Si 2 O 7 compositions. Tauc-plots of the VUV reflection spectra of these compounds were used to derive the optical band gaps, which are in the range between 6.2 and 7.1 eV. The single phase samples show strong photoluminescence in the UV and visible range upon excitation by VUV radiation or by electron bombardment. PL spectra have been measured by 160 nm excitation and cathode luminescence (CL) spectra have been recorded at electron beam energies between 2 and 20 keV, respectively. All measurements reveal that the pyrosilicates show strong defect luminescence, whereby the observed broad emission bands are assigned to different defect types.

Optically active cluster compounds [W6Br8L6]2– are prepared from Cs2[W6Br14], which is obtained via reduction of WBr6 with elemental antimony in the presence of CsBr. Cesium ions and six apical bromide ligands of Cs2[W6Br14] are successively replaced for n-tetrabutyl ammonium (TBA)+ and ligands (L). Light yellow single-crystals of (TBA)2[W6Br8L6] with L = CF3COO and C7H7SO3 were isolated from dichloromethane solution and structurally characterized by means of X-ray single-crystal diffraction. Photoluminescence studies reveal a wide excitation range within 250 to 500 nm for both compounds and a broad emission centered at λem,max = 735 nm (L = CF3COO) and 730 nm (L = C7H7SO3). Oxygen dependencies of emission intensities are reported.

Two new series of tetracyanamidogermanates were prepared by solid-state reaction of appropriate amounts of REF3 (RE = rare earth), A2[GeF6] (A = alkaline), and Li2(CN2) in evacuated silica tubes. Powder X-ray diffraction patterns of crystalline samples of KRE[Ge(CN2)4] and CsRE[Ge(CN2)4] were indexed isotypically to KRE[Si(CN2)4] and RbRE[Ge(CN2)4], respectively. Luminescence properties of Ce3+, Eu3+, and Tb3+ doped compounds and non-linear optical properties (NLO) of KRE[Ge(CN2)4] are reported.

The phase Li

The heteroleptic cluster compound (W6I8)Cl4 was prepared by thermal conversion of the homoleptic clusters W6I12 and W6Cl12 at 700 °C to yield a bright yellow powder. The presence of the smaller chlorido ligands in apical positions of [(W6I8)Cl6]2– creates nearly spherically clusters showing thermal and chemical inertness. Photoluminescence studies revealed a strong red phosphorescence from excited spin-triplet states.

Europium doped small particles presently receive great attention due to their excellent photoluminescent (PL) intensity, (photo)chemical stability, and linearity in the orange-red spectral region and find challenging biomedical application. Europium doped compounds are extremely good candidates for optical imaging due to stable luminescence, long fluorescence decay time, sharp emission peaks, i.e. narrow band width, in the red to near-infrared (NIR) region. Moreover, lasers based on red emission of europium also could be an attractive choice for medical application since NIR radiation can penetrate biological tissues such as human skin. This study allows to discuss luminescent properties of europium (5 at-% or 30 at-%) doped Y3Al5O12 and Y3Ga5O12 garnets in single crystals and powders. Europium enabled luminescent properties are discussed based on the concentration of europium and dopant local environment. All these compounds possess dominant 5D0 → 7F4 emission in the NIR region and are thus potential candidates for optical imaging.

Carbodiimides are a growing group of compounds, which raised interest as hosts for luminescent materials. Ca(CN2) doped with 5, 10 and 50 mol% Mn2+ was synthesized by a solid-state metathesis reaction at rather low temperature. The unit cell volume of Ca(CN2) decreases with increasing the Mn2+ concentration. The emission spectra of the doped material show an emission band in the red spectral range originating from the 4T1g(4G)–6A1g(6S) transition.

Europium(III) compounds with the compositions Eu2(CN2)3 and KEu[Si(CN2)4] were prepared by solid-state metathesis reactions. The europium(III) carbodiimide was prepared by the reaction of EuF3 and Li2CN2, while the europium(III) tetracyanamidosilicate was prepared from EuF3, K2SiF6, and Li2CN2. Their crystal structures were refined from powder XRD data with space groups C2/m for Eu2(CN2)3 and P21212 for KEu[Si(CN2)4]. Luminescence spectra of Eu2(CN2)3 and KEu[Si(CN2)4] as well as nonlinear optical properties of KEu[Si(CN2)4] are reported. The two synthesized compounds are the missing members of the rare earth metal carbodiimide and tetracyanamidosilicate series.

The synthesis, characterization, and luminescence properties of (Bu4N)2[Mo6I8(NCS)6] are reported. Orange crystals of (Bu4N)2[Mo6I8(NCS)6] were crystallized from acetone solution and used for X-ray single-crystal structure determination and refinement, yielding a structure with a centrosymmetric [Mo6I8(NCS)6]2– ion. Photoluminescence studies on the crystalline solid revealed a broad excitation in the UV/Vis region and an emission around 690 nm. The red emission intensity decreases with increasing partial pressure of atmospheric molecular O2.

The new nitridoborate nitride Mg3Ga(BN2)N2 was prepared by multilateral solid-state metathesis reaction from MgCl2, GaN, Li3N, and Li3BN2 at high temperature. The crystal structure of Mg3Ga(BN2)N2 was refined from X-ray powder diffraction patterns isotypically to Mg3Al(BN2)N2 with the space group Rm no.166 [Z = 3, a = b = 3.4560(0) A, c = 31.7924(2) A]. The undoped and Eu2+-doped Mg3Ga(BN2)N2 show orange-red luminescence under UV excitation.

Terbium-substituted KYW2O8 single crystals of high optical quality were grown by the top seeded solution growth technique. The degree of yttrium–terbium mixed occupancy was determined for two samples through structure refinements on the basis of single crystal X-ray diffractometer data. Temperature dependent magnetic susceptibility data underline the paramagnetic nature of terbium doped crystals. No magnetic ordering is evident down to 2 K. Luminescence measurements yield the typical excitation and emission spectra as expected for Tb3+ activated materials. The decay time of Tb3+ decreases linearly with the Tb3+ concentration, while the excess of thermal quenching does not change significantly. At about 405 K the decay time is reduced by roughly 50% relative to the low-temperature value, both for the powders as for the single crystals.

High-quality single crystals of partially europium-substituted KYW 2 O 8 (KYW) were grown by the top-seeded solution growth technique. The structures of four crystals with different europium content were refined on the basis of single crystal X-ray diffractometer data. The trivalent character of europium in these crystals was manifested through 151 Eu Mossbauer spectra and magnetic susceptibility measurements. Moreover, reflection and photoluminescence spectra were recorded and from these spectra the quantum efficiency, lumen equivalent, and CIE1931 color point were calculated. It turned out that Eu 3+ doped KYW is an efficient photoluminescent material at room temperature, while the thermal quenching temperature T 1/2 is at about 633 K (360 °C), thus making the material a potential radiation converter for light emitting diodes.

Compounds Mg8–xMx(BN2)2N4 were prepared by solid-state reaction of MgCl2, Li3(BN2), and AlN for M = Al, and of Mg3N2, BN, and Si3N4 for M = Si. Their crystal structures were refined from powder X-ray diffraction data with the space group Rm for M = Al, Si, and P21/c for M = Si. The structures of Mg8–xMx(BN2)2N4 are characterized by layered arrangements of wurtzite-related block layers alternating with a layer of di-nitridoborate ions along the c-axis direction. Cations in each structure are surrounded tetrahedrally by nitride and di-nitridoborate ions. Europium(II)-doped powders of Mg8–xMx(BN2)2N4 show exceptional broad band emissions in the visible region of the spectrum, on excitation with UV radiation at λex = 320 nm.

Mg3(BN2)N was prepared by solid state metathesis reactions and several europium (Eu2+) doped samples were prepared to discover novel red-emitting photoluminescent (PL) materials. It turned out that the undoped and doped samples showed very broad deep-red photoluminescence ranging from about 500 nm into the near infrared. Due to the similar spectra of the undoped and doped samples and unusually high FWHM values of about 5780 cm–1 we conclude that the luminescence process originates from defect sites. This was confirmed by decay measurements which show that the decay constants for all samples were in the range of several milliseconds.

New ternary cyanamide compounds isostructural to LiY(CN 2 ) 2 were obtained by solid state metathesis reaction. The crystal structure of LiAl(CN 2 ) 2 was determined by single crystal X-ray diffraction, the structures of LiIn(CN 2 ) 2 and LiYb(CN 2 ) 2 were solved from X-ray powder diffraction data. Photoluminescence properties of Tb 3+ -doped LiIn(CN 2 ) 2 are reported too.

Orthoperiodates of calcium, strontium, and barium were prepared by solid-state reactions of metal iodides or metal iodates with oxygen in air. M(IO3)2 (M = Ca) or MI2 (M = Sr, Ba) were heated in an open corundum crucible to yield M5(IO6)2 as a product with beige to light brown body color. Reactions were investigated by thermal analyses, using differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Two distinct crystal structures were assigned for M5(IO6)2 with the space group Rc for M = Ca, Sr (isotypic with Ca, Sr perrhenates) and Pnma for M = Ba based on recorded powder X-ray diffraction data. Luminescence properties of europium-doped samples are reported.

Rare earth cyanurates were prepared by exothermic solid-state metathesis reactions of appropriate proportions of A(OCN) (A = K, Rb, Cs) and RECl3 (RE = La, Ce, Pr) at 500 °C. A DTA study of this mixture revealed the reaction to occur around 450 °C. The crystal structure of RbLa2Cl(O3C3N3)2 was refined from a powder X-ray diffraction pattern. Homologous ARE2Cl(O3C3N3)2 compounds with A = K, Rb, Cs and RE = La, Ce, Pr were indexed isotypically. Photoluminescence and reflection properties of doped samples and an infrared study are reported.