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The compound Ta 4 SBr 11 was prepared by a comproportionation reaction of tantalum bromide with tantalum and elemental sulfur. The crystal structure, as refined by single-crystal X-ray diffraction, is composed of clusters with Ta 4 S cores, arranged in corrugated van der Waals layers. Individual layers appear to be displaced relative to each other along one direction. Successful crystal growth in a melt of CsBr yielded black platelets of Ta 4 SBr 11 , which were used to investigate the electrical properties of the compound. The electronic structure was studied by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and by density functional theory (DFT) band structure calculations, revealing this material to be a small-gap semiconductor. DFT results, in combination with magnetic susceptibility measurements, suggest that metallicity originating from the one unpaired Ta d electron per cluster is most likely suppressed by electronic correlations, forming a cluster Mott insulator.

The reaction of 2-aminobiphenyl ArNH 2 with triethylamine borane (Et 3 NBH 3 ) at 165 °C, about 40 °C lower in temperature than that used for borazine synthesis, gives a linear HArN-BH-NAr-BH-NArH (Ar = [1,1'-biphenyl]-2-yl) chain in good yield (57%). This BN oligomer could be characterized by single crystal X-ray crystallography.

A novel and more efficient synthesis of Cu 3 (C 3 N 6 H 3 ) is presented through a salt-metathesis reaction using copper(I) chloride and sodium hydrogen cyanamide. This synthesis yields a melaminate trianion through the cyclotrimerization of (HNCN) - ions, offering an alternative route to the deprotonation of melamine for synthesizing melaminate. The reaction is analyzed via differential thermal analysis. After the unconventional formation of this MOF-like structure by solid-state reaction, this material still requires treatment via solvent exchange and vacuum drying due to the presence of a host molecule inside the channels of the structure. The process and the impact of the treatment of Cu 3 (C 3 N 6 H 3 ) on its XRD pattern are thoroughly discussed. Additionally, results from stability, NMR and infrared spectroscopy, and thermogravimetric analysis. Finally, photoluminescence and magnetic studies are conducted to evaluate their potential as a functional material.

Benzoborirene carrying a bulky Trip 2 C 6 H 3 (Trip = 2,4,6-tri-iso-Pr 3 C 6 H 2 ) group at boron reacts with the dienophile 4-phenyl-1,2,4-triazoline-3,5-dione and the diene 3,6-di(4-pyridyl)-1,2,4,5-tetrazine by opening of the borirene ring rather than undergoing the typical Diels-Alder reactions. The formal insertion results in diazaborole and azaborolo[1,5- b ][1,2,4,5]tetrazine derivatives, respectively.

Thermal analysis techniques, such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), can provide valuable insights into thermal properties, intermediate phases, and phase transitions; sometimes even a whole series of compounds appears in a given system. The solid-state reaction pathway from melamine to carbodiimide, monitored by DSC, involves a sequence of chemical reactions and intermediate phases departing from the reaction of potassium hydride and melamine. The fully analyzed reaction cascade begins with the formation of potassium melaminate, K(C 3 N 6 H 5 ), and progresses through several intermediate phases, each with distinct structures and properties, before ultimately yielding β-K 2 (CN 2 ). All crystalline compounds appearing in this reaction sequence are identified using X-ray diffraction analyses. With a 6:1 ratio of potassium hydride and melamine, equal numbers of protic and hydridic hydrogen atoms in the starting materials favor the release of H 2 until the formation of the final product K 2 (CN 2 ), which appears with two modifications.

Molecular solar thermal systems (MOST) represent an auspicious solution for the storage of solar energy. We report silver salts as a unique class of catalysts, capable of releasing the stored energy from the promising 1,2-dihydro-1,2-azaborinine based MOST system. Mechanistic investigations provided insights into the silver catalyzed thermal backreaction, concurrently unveiling the first crystal structure of a 2-aza-3-borabicyclo[2.2.0]hex-5-ene, the Dewar isomer of 1,2-dihydro-1,2-azaborinine. Quantification of activation energies by kinetic experiments has elucidated the advantageous energy change associated with Lewis acid catalysts, a phenomenon corroborated through computational analysis. By means of low temperature NMR spectroscopy, mechanistic insights into the coordination of Ag + to the 1,2-dihydro-1,2-azaborinine were gained., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Thiourea S -oxides are labile compounds that suffer from a quick overoxidation when directly prepared from thioureas. Therefore, we have developed an alternative route on the basis of the SO transfer from a thiirane S -oxide onto sterically encumbered N -heterocyclic carbenes, including imidazole- and imidazoline-ylidenes, and a cyclic alkyl amino carbene. Reaction conditions and DFT computations suggest a concerted SO transfer mechanism. Thiourea S -oxides are nucleophiles adding to dimethyl acetylenedicarboxylate under fission of the S-O bond.

The thermal condensation of melamine into molecules melam, melem, and the one-dimensional polymer melon has already been reported. An interesting question arises about the impact of other compounds being present in this process of thermal conversion. The solid-state reaction of C 3 N 6 H 6 with InCl 3 leads to a novel compound featuring deprotonated melam units in a supramolecular assembly, based on the [C 12 N 20 H 8 ] 4- anion that is interconnected in the structure via N-In-N bonding. The reaction pathway of the formation of this compound is investigated by thermal analysis and the crystal structure of unique (NH 4 )[(InCl 2 ) 3 (C 12 N 20 H 8 )]·⅔[InCl 3 (NH 3 )] is reported as well as its photoluminescence properties.

The crystal structures of ANb 3 Br 7 S (A = Rb and Cs) have been refined by single crystal X-ray diffraction, and are found to form highly anisotropic materials based on chains of the triangular Nb 3 cluster core. The Nb 3 cluster core contains seven valence electrons, six of them being assigned to Nb-Nb bonds within the Nb 3 triangle and one unpaired d electron. The presence of this surplus electron gives rise to the formation of correlated electronic states. The connectivity in the structures is represented by one-dimensional [Nb 3 Br 7 S] - chains, containing a sulphur atom capping one face (μ 3 ) of the triangular niobium cluster, which is believed to induce an important electronic feature. Several types of studies are undertaken to obtain deeper insight into the understanding of this unusual material: the crystal structure, morphology and elastic properties are analysed, as well the (photo-)electrical properties and NMR relaxation. Electronic structure (DFT) calculations are performed in order to understand the electronic structure and transport in these compounds, and, based on the experimental and theoretical results, we propose that the electronic interactions along the Nb chains are sufficiently one-dimensional to give rise to Luttinger liquid (rather than Fermi liquid) behaviour of the metallic electrons.

The development of new compounds in the domain of metal dinitridocarbonates is most efficiently performed via solid-state metathesis or simply by addition reactions. Our discovery of Pb 7 I 6 (CN 2 ) 4 is the result of a solid-state reaction of PbCN 2 with PbI 2 at 420 °C. Its crystal structure was solved and refined from X-ray diffraction data based on a single crystal with the space group P 6 3 / mmc . The crystal structure is based on a network of lead tetrahedra, lead trigonal bipyramids and lead octahedra interconnected by [NCN] 2- and iodide. Properties of the material were investigated by diffuse reflection measurement, photoluminescence measurements, and electronic band structure calculations demonstrating that this material is a semiconductor.

Benzoborirenes are a very rare class of strained boron heterobicyclic systems. In this study a kinetically stabilized benzoborirene 1 is shown to react with multiple bonds of trimethylphosphine oxide, acetaldehyde, and tert -butyl isonitrile. The (2 + 2) cycloaddition product with trimethylphosphine oxide, benzo[ c ][1,2,5]oxaphosphaborole, has a long apical PO bond (194.0 pm) that must be considered on the border line between ionic and covalent according to the natural bond orbital, quantum theory of atoms in molecules, and compliance matrix approaches to the description of chemical bonding. The coordination compound between the benzoborirene and phosphine oxide was observed by NMR spectroscopy at 213 K. The Lewis acidity of 1 is similar to that of B(OCH 2 CF 3 ) 3 and B(C 6 F 5 ) 3 based on the 31 P{ 1 H} NMR chemical shift of the Lewis acid base complexes with trimethylphosphine oxide at 213 K. Benzoboriene 1 does not react with acetone, but forms a (2 + 2) cycloaddition product, an oxaborole, with acetaldehyde. In contrast, it undergoes a double (2 + 1) reaction with tert -butyl isonitrile to yield a boro-indane derivative under mild conditions. The observed reactivity of 1 is in agreement with computational analyses of the respective potential energy surfaces., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Solvated tungsten iodide cluster compounds are presented with the homoleptic cluster cation [(W 6 I 8 )(CH 3 CN) 6 ] 4+ and the heteroleptic [(W 6 I 8 )I(CH 3 CN) 5 ] 3+ , synthesized from W 6 I 22 in acetonitrile. Crystal structures were solved and refined on deep red single-crystals of [(W 6 I 8 )(CH 3 CN) 6 ](I 3 )(BF 4 ) 3 ·H 2 O, [(W 6 I 8 )I(CH 3 CN) 5 ](I 3 ) 2 (BF 4 ), and on a yellow single-crystal of [W 6 I 8 (CH 3 CN) 6 ](BF 4 ) 4 ·2(CH 3 CN) on the basis of X-ray diffraction data. The structure of the homoleptic [(W 6 I 8 )(CH 3 CN) 6 ] 4+ cluster is based on the octahedral [W 6 I 8 ] 4+ tungsten iodide cluster core, coordinated by six apical acetonitrile ligands. The electron localisation function of [(W 6 I 8 )(CH 3 CN) 6 ] 4+ is calculated and solid-state photoluminescence and its temperature depedence are reported. Additionally, photoluminescence and transient absorption measurements in acetonitrile are shown. Results of the obtained data are compared to compounds containing [(M 6 I 8 )I 6 ] 2- and [(M 6 I 8 )L 6 ] 2- (M = Mo or W; L = ligand) clusters.

Thiourea S-oxides can be viewed as formal analogs of the currently unknown diamino-substituted Criegee intermediates (urea O-oxides). However, the preparation of such S-oxides is rather challenging, and the direct oxidation of thioureas typically only leads to formation of desulfurized products. Employing the accurate revDSD-PBEP86-D4 double hybrid density functional, it was found that the peracid mediated oxidation of thiourea S-oxides exhibits a lower reaction barrier than the oxidation of the corresponding thiourea itself in contrast to most other ordinary thioketones. The undesired overoxidation reactivity, which is associated with strong π-donation from the thiourea's nitrogen atoms, can be partially suppressed by introduction of bulky substituents and the utilization of protic solvents. In this regard, we managed to prepare two sterically encumbered thiourea S-oxides in isolated yields of 35-40 %. The S-oxides are stable in the solid state and in alcoholic solutions at room temperature for extended periods of time, but swiftly decompose in aprotic solvents by disproportionation. A dimesityl-substituted thiourea S-oxide complexed with residual mCBA could be characterized by means of X-ray crystallography, confirming the importance of hydrogen bonding in the stabilization of the amino-substituted C=S + -O - moiety., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Niobium pnictide halides Nb 4 PnX 11 ( Pn = N, P; X = Cl, Br, I) are reported with their average crystal structures. Individual pnictide-capped butterfly cluster cores [Nb 4 P] in the structure are interconnected into two-dimensional layers, with their electronic and magnetic properties being analyzed.

Formal reduction of (2-bromophenyl)chloro(2,2'',4,4'',6,6''-hexaisopropyl-[1,1':3',1''-terphenyl]-2'-yl)borane with tert -butyl lithium at low temperatures yields a highly strained benzoborirene that is kinetically stabilized by the bulky terphenyl substituent. The target compound withstands heating to 80 °C, and represents the first benzoborirene fully characterized by single-crystal X-ray crystallography. The bond length pattern of the six-membered ring of the parent benzoborirene follows an anti-Mills-Nixon distortion.

The synthesis of Nb 4 S 3 , a previously undiscovered binary sulfide, was achieved using Nb 3 Br 7 S as a precursor. Its structure is composed of Nb 6 S triangular prisms arranged in a polar ( Imm 2) configuration, with sulfur atoms lying in channels along the a axis. Electrical resistivity measurements and density functional theory calculations were used to determine that Nb 4 S 3 is metallic and therefore a polar metal, with metallic bands occupied by electrons with primarily niobium character. The electrons near the Fermi level are so closely associated with the niobium sublattice that the sulfur atoms have positive Born effective charges, indicating that the electrostatic interactions between sulfur atoms are unscreened. Calculations of the dependence of the electron density on the sulfur atomic positions confirm that the metallic electrons do not screen the dipole-dipole interactions between sulfur atoms, which allows polarity and metallicity to coexist in Nb 4 S 3 . These findings suggest that applied electric fields might be able to reverse the polarity of thin films of Nb 4 S 3 .

Crystals of Cu 3 (C 3 N 6 H 3 ) are formed by a solid-state reaction of CuCl with melamine to form a layered framework structure with open pores running along the hexagonal axis direction of the P 6/ mcc structure. The compound contains the hitherto unknown (C 3 N 6 H 3 ) 3- ion, assigned as melaminate. Bonding interactions within and between Cu-Cu dumbbells, which connect melaminate ions into layers, are analyzed by density functional theory calculations of the electron localization function and directional Young's modulus. Band structure calculations reveal the material to be a semiconductor with a band gap on the order of 2 eV.

The crystal structures of the hitherto unknown phase W2O3I4 and of WO2I2, a compound that is known to play an important role in the chemical vapor transport of elemental tungsten are reported. We demonstrate that WO2I2 transforms into W2O3I4, and then into WO2 with increasing temperature. Crystals of WO2I2 appear as thin platelets, showing metallic luster; crystals of W2O3I4 appear as black colored needle-shaped platelets. Both compounds adopt layered structures; electronic band structure calculations reveal metallic conductivity for W2O3I4 and surprisingly also for WO2I2.

The new compound WTe 2 I was prepared by a reaction of WTe 2 with iodine in a fused silica ampule at temperatures between 40 and 200 °C. Iodine atoms are intercalated into the van der Waals gap between tungsten ditelluride layers. As a result, the WTe 2 layer separation is significantly increased. Iodine atoms form planar layers between each tungsten ditelluride layer. Due to oxidation by iodine the semimetallic nature of WTe 2 is changed, as shown by comparative band structure calculations for WTe 2 and WTe 2 I based on density functional theory. The calculated phonon band structure of WTe 2 I indicates the presence of phonon instabilities related to charge density waves, leading to an observed incommensurate modulation of the iodine position within the layers.

A series of new compounds MI(OCN) were prepared from the mixtures of MI 2 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 [M 2 I 2 ] 2+ blocks separated by single layers of cyanate ions that are found to be related to the Sillén-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 Eu 2+ . The luminescence spectra recorded under excitation at 340 and 350 nm revealed a blue emission of Eu 2+ 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 4f 6 5d 1 → 8 S 7/2 (4f 7 ) transition.

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 properties as well as solid-state structures, singlet fission, and organic field-effect transistor (OFET) performance of three tetrafluoropentacenes (1,4,8,11: 10, 1,4,9,10: 11, 2,3,9,10: 12) are compared herein. The novel compounds 10 and 11 were synthesized in high purity from the corresponding 6,13-etheno-bridged precursors by reaction with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate at elevated temperatures. Although most of the molecular properties of the compounds are similar, their chemical reactivity and crystal structures differ considerably. Isomer 10 undergoes the orbital symmetry forbidden thermal [4+4] dimerization, whereas 11 and 12 are much less reactive. The isomers 11 and 12 crystallize in a herringbone motif, but 10 prefers π-π stacking. Although the energy of the first electric dipole-allowed optical transition varies only within 370 cm -1 (0.05 eV) for the neutral compounds, this amounts to roughly 1600 cm -1 (0.20 eV) for radical cations and 1300 cm -1 (0.16 eV) for dications. Transient spectroscopy of films of 11 and 12 reveals singlet-fission time constants (91±11, 73±3 fs, respectively) that are shorter than for pentacene (112±9 fs). OFET devices constructed from 11 and 12 show close to ideal thin-film transistor (TFT) characteristics with electron mobilities of 2×10 -3 and 6×10 -2  cm 2  V -1  s -1 , respectively., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The formation of the new compound Sn 9 O 5 Cl 4 (CN 2 ) 2 is reported and placed in the context of several other recently discovered tin carbodiimide compounds (Sn(CN 2 ), Sn 2 O(CN 2 ), and Sn 4 Cl 2 (CN 2 ) 3 ), all of which contain divalent tin. The crystal structure of Sn 9 O 5 Cl 4 (CN 2 ) 2 , as determined by X-ray powder diffraction, includes an unusual [Sn 8 O 3 ] cluster, in which tin atoms form the motif of a hexagonal bipyramid. An additional tin atom and two oxygen atoms connect these clusters into chains. Mössbauer spectroscopy shows tin to predominantly adopt the +2 oxidation state, and electronic structure calculations predict Sn 9 O 5 Cl 4 (CN 2 ) 2 to be a semiconductor.

In search of iodine-rich compounds with an octahedral tungsten cluster, we explored the treatment of β-W 6 I 12 , the most stable tungsten iodide cluster compound, with liquid iodine. The most iodine-rich compound obtained from these reactions was W 6 I 22 , whose crystal structure adopts two closely related modifications. The remarkable connectivity of [W 6 I 8 ] 4+ clusters in the structure of W 6 I 22 makes this compound the first example of a soluble binary octahedral tungsten iodide cluster, as demonstrated by dissolution experiments in several solvents. Differential scanning calorimetry showed that the thermolysis of triclinic α-W 6 I 22 proceeds via a phase transformation into monoclinic β-W 6 I 22 , followed by the formation of W 6 I 18 and W 6 I 16 with release of iodine. A corresponding ambient-pressure study by combined differential thermal analysis and thermal gravimetry revealed the transformation of β-W 6 I 22 into W 6 I 14 and β-W 6 I 12 , which finally decomposes into the elements. On the basis of this simple example, we demonstrate how a complete reaction sequence, including preparation and subsequent phase transformations, can be monitored and analyzed by thermal scanning methods. Moreover, a reaction cycle is reported that relates a whole series of binary tungsten iodides. Syntheses of the new compounds α- and β-W 6 I 22 , and W 6 I 14 are reported, and their crystal structures, as determined by X-ray diffraction techniques, are presented.

The phase Li x Ca 16-x Si 17 N 32-x O 2+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 F4[combining macron]3m (a = 14.7391(1) Å, Z = 4); it is closely related to the previously reported structure of Ca 16 Si 17 N 34 . The structure of Li x Ca 16-x Si 17 N 32-x O 2+x is based on a complex network of [SiN 4 ] 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 Eu 2+ emission at 536 nm on excitation with near-UV or blue radiation at 350-480 nm. Ce 3+ doping yields orange to red emission with two broad emission bands at 600 and 665 nm.

Yellow transparent single crystals of the new compound K2Pb(OCN)I3 were synthesized from a mixture of lead iodide and potassium cyanate through a solid-state reaction, which was controlled by the differential scanning calorimetry (DSC) technique. The single crystal X-ray refinement showed that K2Pb(OCN)I3 crystallizes in the cubic system (Fd3[combining macron]m, a = 16.295(2) Å, V = 4327(1) Å3, Z = 16 and R1 = 0.0167). The structure is basically composed of two frameworks built from potassium tetrahedra capped by OCN- units and corner-sharing lead iodide octahedra. The infrared spectrum of K2Pb(OCN)I3 reveals the presence of vibration modes that were assigned to cyanate ions. The band structure and total and partial density of states calculated by DFT with the PBE functional (CASTEP code) showed that this compound exhibits a direct band gap of 2.19 eV, which is in good agreement with the experimental value obtained from a diffuse reflectance measurement (2.4 eV). The investigation of the electrical properties of this material demonstrates that it is highly resistive and has large permittivity (relative values of up to 104 at 150 °C). However, it does not display ferroelectric behavior.

A solid-state metathesis reaction between equimolar amounts of Li 2 (CN 2 ) and SnCl 2 revealed the formation of two new compounds, Sn 4 Cl 2 (CN 2 ) 3 and Sn(CN 2 ). Thermal analysis of this reaction indicated that Sn 4 Cl 2 (CN 2 ) 3 forms exothermically near 200 °C and subsequently transforms into Sn(CN 2 ) at higher temperatures. The crystal structures of both compounds are presented. According to optical measurements and band structure calculations, Sn(CN 2 ) can be considered as a semiconductor with a band gap on the order of 2 eV. The presence of Sn 2+ ions in the structure of Sn(CN 2 ) with a toroidally shaped lone pair is indicated by electron localization function calculations. The structure of Sn(CN 2 ) is shown to be related to the structures of FeS 2 and CaC 2 .

The photophysics of selected tungsten iodide clusters was examined with respect to their role as a photosensitizer for the production of singlet oxygen, O 2 (a 1 Δ g ). We examined all-iodo octahedral clusters, [W 6 I 8 (I 6 )] 2- , and ligand-substituted octahedral clusters, [W 6 I 8 (L 6 )] 2- , in which the ligand, L, occupies the outer apical positions surrounding the cluster core. We also examined a square-pyramidal cluster, [W 5 I 8 (I 5 )] - , in which the tungsten core was presumably more accessible to diffusional encounter with ground state oxygen, O 2 (X 3 Σ g - ). For the compounds examined, we find pronounced cluster-dependent changes in the yield of photosensitized O 2 (a 1 Δ g ) production. In particular, although the iodine-encased octahedral cluster, [W 6 I 8 (I 6 )] 2- , is an efficient O 2 (a 1 Δ g ) sensitizer, the pyramidal cluster, [W 5 I 8 (I 5 )] - , does not make O 2 (a 1 Δ g ) at all. The latter provides fundamental insight into the important case where the sensitizer triplet state is nearly degenerate with the O 2 (X 3 Σ g - )-O 2 (a 1 Δ g ) transition energy at 1 eV. Our data indicate that even with near resonance, energy transfer to form O 2 (a 1 Δ g ) will not occur within the 3 sensitizer-O 2 (X 3 Σ g - ) encounter pair if other more efficient channels for energy dissipation are available.

The preparation of binary tungsten iodides by the reaction of elements is intrinsically difficult because most compounds are only stable at temperatures where the reaction rates between elemental tungsten and iodine are too low. Therefore, other preparative procedures have to be developed. Two synthetic methods have previously been reported for binary tungsten iodides: halide exchange reactions starting from tungsten chloride, and the reaction of tungsten hexacarbonyl with elemental iodine. These two methods have lead to the discovery of a number of binary tungsten iodide compounds. However, how many compounds can be expected in a binary sytem? A recently developed synthetic method has opened Pandora's box, leading to the discovery of a tremendous number of new binary tungsten iodide compounds with structures which have never been seen before in metal halide chemistry. The formation of binary tungsten iodides depends on a subtle interplay of pressure and temperature conditions as can be monitored by thermal scanning under variable I 2 partial pressures. More than twenty binary tungsten iodide compounds with trigonal, tetrahedral, square pyramidal, and octahedral cluster cores are summarized in this review with their formation conditions, crystal structures, and transformation reactions. These preparative advances open new frontiers in metal halide chemistry and give an impact to the chemistry of octahedral [W 6 I 8 ] 4+ cluster compounds which can serve as powerful phosphorescent materials and singlet oxygen generators.

The compound Sn2O(CN2) was obtained as a brick-red crystalline powder from a solid-state reaction of equimolar amounts of SnCl2, SnO and Li2(CN2). Thermal analysis of the reaction indicates the formation of two intermediate compounds until Sn2O(CN2) is formed at 400 °C. The crystal structure of Sn2O(CN2) was determined in the space group Pccn (a = 13.3949(7) Å, b = 5.2954(3) Å, c = 5.5369(2) Å, Z = 4) from single-crystal X-ray diffraction data. The structure contains a Sn2+ ion with a 5s2 lone pair, situated in a fourfold, mixed O-/N-coordination environment. The crystal structure of Sn2O(CN2) is analyzed and discussed in relation to that of SnO, namely by electronic-structure calculations and a COHP bonding analysis of Sn2O(CN2).

Ag 2 [W 6 I 14 ] and A 2- x [W 6 I 14 ] compounds with A = Na, Li were prepared from binary tungsten iodides (W 3 I 12 ) and corresponding metal iodides. Their crystal structures are analyzed on the basis of X-ray diffraction data. 7 Li and 23 Na solid-state NMR measurements reveal that Li + and Na + ions are distributed over two sites in the respective structures. These results shed some new light on A x [M 6 I 14 ] with A = alkali and M = Mo, W compounds being reported with x = 1 and 2, which exhibit photophysical properties. The lithium compound is an exception in the series of A 2- x [W 6 I 14 ] compounds, because it is the only compound which is soluble in water.

Tungsten iodide compounds feature a surprising diversity of binary compounds. Their formation conditions and phase equilibria depend very much on the surrounding iodine partial pressure and temperature. Herein we focus on square-pyramidal tungsten iodide cluster compounds with their iodine loss, structural rearrangements, cross-linking behavior, and final transformation into the octahedral cluster compound β-W 6 I 12 at elevated temperatures. Reactions depart from W 5 I 16 at different iodine pressures and temperatures. The thermal decomposition of W 5 I 16 at low iodine pressure passes through a number of cluster compounds (W 5 I 15 , W 5 I 13 ·xI 2 , β-W 5 I 12 , and W 5 I 11 ) under release of iodine. At higher iodine pressures, only one intermediate compound (α-W 5 I 12 ) was found. Thermal decomposition of W 5 I 16 was examined by differential thermal/thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction (XRD) measurements. New compounds (W 5 I 15 , W 5 I 13 ·xI 2 , and W 5 I 11 ) were structurally characterized by means of XRD techniques. The crystal structure of W 5 I 11 reveals a nice relationship to its transformation product W 6 I 12 .

The reduction of tungsten hexachloride with lead powder was investigated by differential scanning calorimetry (DSC) combined with X-ray diffraction (XRD) studies. Intermediate compounds along the way of the reduction of W 6+ to W 2+ were detected, prepared by solid-state synthesis, and structurally characterized by X-ray diffraction techniques. Five new compounds, namely Pb 0.5 WCl 6 , PbW 2 Cl 10 , Pb 1.5 [W 3 Cl 13 ], Pb 2 Cl[W 3 Cl 13 ], and Pb[W 6 Cl 14 ] are discovered to be formed with increasing temperature, and structurally characterized within this study. The analysis of the reduction pathway is meant to gain a better understanding of the metallothermic reduction process and intercalation chemistry in the solid state.

A reaction cycle is shown for octahedral tungsten iodide compounds. The thermal transformation of W 6 I 16 (W 6 I 12 ·2I 2 ) via release of iodine proceeds via the new W 6 I 13 (W 6 I 12 ·xI 2 with 0 < x ≤ 1/2) to yield a new modification of W 6 I 12 , denoted as α-W 6 I 12 . When heated, α-W 6 I 12 is converted into the known (β-)W 6 I 12 . The reaction of (β-)W 6 I 12 with I 2 leads to the formation of the starting compound W 6 I 16 . The new compounds W 6 I 13 (W 6 I 12 ·xI 2 with 0 < x ≤ 1/2) and α-W 6 I 12 are structurally characterized by powder and single-crystal X-ray diffraction techniques. The thermal decomposition of W 6 I 16 and the monotropic phase transition of α-W 6 I 12 into β-W 6 I 12 are examined by differential scanning calorimetry measurements.

Background: Carbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements (including hydrogen and oxygen). The toxicity of CBNP has been attributed to their large surface area, and through adsorbing intrinsically toxic substances, such as polycyclic aromatic hydrocarbons (PAH). It is not clear whether a PAH surface coating changes the toxicological properties of CBNP by influencing their physicochemical properties, through the specific toxicity of the surface-bound PAH, or by a combination of both., Methods: Printex ® 90 (P90) was used as CBNP; the comparators were P90 coated with either benzo[a]pyrene (BaP) or 9-nitroanthracene (9NA), and soot from acetylene combustion that bears various PAHs on the surface (AS-PAH). Oxidative stress and IL-8/KC mRNA expression were determined in A549 and bronchial epithelial cells (16HBE14o-, Calu-3), mouse intrapulmonary airways and tracheal epithelial cells. Overall toxicity was tested in a rat inhalation study according to Organization for Economic Co-operation and Development (OECD) criteria. Effects on cytochrome monooxygenase (Cyp) mRNA expression, cell viability and mucociliary clearance were determined in acute exposure models using explanted murine trachea., Results: All particles had similar primary particle size, shape, hydrodynamic diameter and ζ-potential. All PAH-containing particles had a comparable specific surface area that was approximately one third that of P90. AS-PAH contained a mixture of PAH with expected higher toxicity than BaP or 9NA. PAH-coating reduced some effects of P90 such as IL-8 mRNA expression and oxidative stress in A549 cells, granulocyte influx in the in vivo OECD experiment, and agglomeration of P90 and mucus release in the murine trachea ex vivo. Furthermore, P90-BaP decreased particle transport speed compared to P90 at 10 μg/ml. In contrast, PAH-coating induced IL-8 mRNA expression in bronchial epithelial cell lines, and Cyp mRNA expression and apoptosis in tracheal epithelial cells. In line with the higher toxicity compared to P90-BaP and P90-9NA, AS-PAH had the strongest biological effects both ex vivo and in vivo., Conclusions: Our results demonstrate that the biological effect of CBNP is determined by a combination of specific surface area and surface-bound PAH, and varies in different target cells.

The low-temperature modification of Sr 3 (O 3 C 3 N 3 ) 2 was prepared and assigned as α-SCY after the high-temperature phase (now called β-SCY) and its frequency-doubling properties were reported recently. The crystal structure of α-SCY was solved and refined by single-crystal X-ray diffraction. Both modifications of SCY crystallize in noncentrosymmetric space groups, with the low-temperature phase (α-SCY) adopting the lower symmetry structure (Cc). Atomic positions in α-SCY (Cc) reveal only small deviations in comparison to those in the structure of β-SCY (R3c). The reversible phase transition between both modifications of SCY was studied by means of temperature-dependent powder X-ray diffraction. NLO measurements of both SCY modifications are reported in comparison to the commercial frequency-doubling material KTiOPO 4 (KTP).

Molybdenum iodides are prepared based on a new way of synthesis, namely, via reductive metathesis reaction of MoCl 5 with SiI 4 . MoI 3 was formed at 150 °C. Mo 6 I 12 and the new molybdenum iodides Mo 6 I 16 and Mo 6 I 18 with the well-known [Mo 6 I 8 ] 4+ cluster core were obtained in the temperature range 550-600 °C. Compounds were structurally characterized by powder and single-crystal X-ray diffraction techniques.

Octahedral tungsten iodide clusters equipped with apical ligands (L) are synthesized to implement substantial photophysical properties. The [W 6 I 8 (CF 3 COO) 6 ] 2- cluster reported herein is the first example of a family of ligand substituted [W 6 I 8 L 6 ] 2- clusters. Such compounds are expected to exhibit a rich photochemistry in which the apical ligands play a crucial role. The versatile solid state and solution phase photophysical properties of (TBA) 2 [W 6 I 8 (CF 3 COO) 6 ] described herein parallel characteristics obtained in some photophysically active organic compounds, including a broad absorption in the UV/VIS region. Upon irradiation of this compound, a broad red emission is observed in the VIS/NIR region resulting from excited triplet states, and singlet oxygen (a 1 Δ g ) is generated in the presence of O 2 .

The preparation of tungsten iodides in large quantities is a challenge because these compounds are not accessible using an easy synthesis method. A new, remarkably efficient route is based on a halide exchange reaction between WCl6 and SiI4. The reaction proceeds at moderate temperatures in a closed glass vessel. The new compounds W3I12 (W3I8 ⋅2 I2) and W3I9 (W3I8 ⋅½I2) containing the novel [W3I8] cluster are formed at 120 and 150 °C, and remain stable in air. W3I12 is an excellent starting material for the synthesis of other metal-rich tungsten iodides. At increasing temperature these trinuclear clusters undergo self-reduction until an octahedral tungsten cluster is formed in W6I12 . The synthesis, structure, and an analysis of the bonding of compounds containing this new trinuclear tungsten cluster are presented., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Inhalation uptake of carbon black nanoparticles (CBNP) bears the risk of morphological and functional lung impairment attributed to the highly reactive particle surface area. Chemical particle surface modifications might affect particle-cell interactions; however, thus far these alterations have not been determined. This is the first in vivo study comparing particle-induced acute lung injury using Printex(®)90 (Pr90, 7 µg), Printex®90 covered by benzo[a]pyrene or 9-nitroanthracene (BaP-Pr90, NA-Pr90, 7 µg, 15% BaP or NA by weight), and acetylene carbon black (CB) with polycyclic aromatic hydrocarbons (PAH-AB, 7 µg, 20% PAH by weight). All particles were suspended in distilled water with bovine serum albumin (BSA). In addition, the influence of suspension media was tested using Printex®90 suspended without BSA (Pr90(-BSA), 7 µg). Quartz (DQ12, 7 µg), 70 µl saline (NaCl), and distilled water with or without BSA (H2O(+/-BSA)) were used as reference and controls. It was postulated that CBNP surface modifications trigger pulmonary responses. After oropharyngeal particle aspiration, lung functions were measured 2 d postexposure, followed by lung preparation for histological or bronchoalveolar lavage fluid (BALF) examinations and type II pneumocyte isolation on d 3. Head-out body plethysmography revealed reduced flow rates induced by PAH-AB. Examinations of BALF demonstrated reduced influx of macrophages after exposure to Pr90(-BSA) and decreased lymphocyte levels after Pr90(+BSA) or BaP-Pr90 treatment. Further, CBNP induced changes in mRNA expressions (surfactant proteins) in type II pneumocytes. These findings indicate that CBNP surface area and media modulate interactions between NP and lung cells in short-term experiments.

Phenomenological studies of WCl6 reduction with transition metal powders M = Mn, Fe, and Co have been recently reported. These reactions involve a series of reductive intercalation steps of M atoms into layered tungsten chloride arrangements, followed by exsolution of MCl2. In the series M = Fe, the presence of divalent iron is evidenced for Fe(x)WCl6, FeW2Cl10, Fe2W2Cl10, and (Fe,W)Cl2 by Mössbauer spectroscopy. Magnetic properties are reported. Bonding characteristics between tungsten atoms in edge-sharing [W2Cl10](n-) bioctahedra reveal that a double bond can be addressed to FeW2Cl10. A similar situation appears for Fe2W2Cl10, due to the localized and thus nonbonding character of the two electrons in the δ orbitals of this compound.

The synthesis of a hexa-peri-hexabenzocoronene (HBC) with a central borazine core is described. The solid-state structure of this BN-doped HBC (BN-HBC) is isotypic with that of the parent HBC. Scanning tunneling microscopy shows that BN-HBC lies flat on Au(111) in a two-dimensional pattern., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A combined thermal scanning-X-ray diffraction (XRD) approach was performed for the WBr(6)-P system to detect and analyze phases in this system, including metal-rich phases generated with increasing amounts of elemental (red) phosphorus under partial PBr(3) release. Phases were characterized by powder XRD. A black crystalline powder of W(4)(PBr)Br(10) was obtained after reduction of WBr(6) with elemental phosphorus at 450 °C. The crystal structure of the new compound was found to be isotypic with the structure of W(4)(PCl)Cl(10) on the basis of powder XRD data. The structure of W(4)(PBr)Br(10) is represented by a cyclobutadiene-like tetranuclear tungsten cluster interconnected into a layered (W(4)(μ(4)-PBr)Br(6)(i))Br(8)/(2)(a-a) arrangement via outer bromide ligands. The μ(4)-capping bromophosphinidene ligand was verified by solid-state magic-angle spinning (31)P NMR spectroscopy.

Calcium cyanurate is synthesized by reacting calcium chloride with potassium cyanate following a solid-state reaction. The formation of the new compound Ca3(O3C3N3)2 (CCY), which occurs by the cyclotrimerization of cyanate ions, was examined thermoanalytically and the crystal structure was determined by single-crystal structure analysis. The structure of CCY is closely related to the structure of the well-known oxoborate β-BaB2O4 (BBO). Second harmonic generation (SHG) measurements on crystal powders show a higher SHG efficiency for CCY than for BBO by about one order of magnitude., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The new cyanurates Sr3(O3C3N3)2 (SCY) and Eu3(O3C3N3)2 (ECY) were prepared via exothermic solid state metathesis reactions from MCl2 (M = Sr, Eu) and K(OCN) in silica tubes at 525 °C. Both structures were characterized by means of powder and single crystal X-ray diffraction, and their structures are shown to crystallize with the noncentrosymmetric space group R3c (No. 161). Infrared spectra and nonlinear optical properties (NLO) of SCY and ECY are reported in comparison to those of CCY and β-BaB2O4 (β-BBO).

The new tetrachloroaurate ethanol hydrate HAuCl4·0.65C2H5OH·1.35H2O was prepared from chloroauric acid trihydrate in ethanol. The compound crystallizes in the triclinic space group P \bar 1 (No. 2). The [AuCl4](-) units in the structure have approximately square-planar symmetry, forming chains parallel to the crystallographic b-axis direction.

The novel metal cyanurates LiSr(O3C3N3) and Li3Sr2F(O3C3N3)2 were prepared by exothermic solid state metathesis reactions and characterized by single crystal X-ray diffraction. Crystalline powders were prepared by reactions of alkali earth halides (SrCl2 and SrF2) with Li(OCN) in 1:3 molar ratios, at 450 and 575 °C. The reaction with chloride yielded LiSr(O3C3N3), and the reaction starting from the fluoride yielded LiSr(O3C3N3)·1/2LiF, containing additional LiF in the structure. Both crystal structures revealed the presence of the (O3C3N3)(3-) ions which were formed by cyclotrimerization reaction of (OCN)(-) ions. The reactions were monitored by differential thermal analysis. Infrared spectra of the compounds are reported.

The preparation of thermally labile compounds is a great temptation in chemistry which requires a careful selection of reaction media and reaction conditions. With a new scanning technique denoted here as Cluster Harvesting, a whole series of metal halide compounds is detected by differential thermal analysis (DTA) in fused silica tubes and structurally characterized by X-ray powder diffraction. Experiments of the reduction of tungsten hexahalides with elemental antimony and iron are presented. A cascade of six compounds is identified during the reduction with antimony, and five compounds or phases are monitored following the reduction with iron. The crystal structure of Fe2W2Cl10 is reported, and two other phases in the Fe-W-Cl system are discussed.

Carbon black nanoparticle (CBNP) applications in high doses have been shown to be harmful to the lung. It is postulated that even small, environmentally relevant concentrations induce changes on lung homeostasis. The present study determined the impact of low-dose single and multiple CBNP (Printex 90) applications on mouse alveolar cell metabolism, especially inflammatory and oxidative stress parameters. Nanoparticles were administered to mice by a single or 8 oropharyngeal aspirations at wk 1, 2, 3, 5, 7, 9, 11, and 12 using 7 μg Printex 90, 7 μg DQ12 quartz (positive control), with water vehicle and saline as negative controls. After 2 d or 3 mo lung function was analyzed. Further lung histology, bronchoalveolar lavage fluid (BALF) parameters, and mRNA expression of cytokines and antioxidants enzymes in type II pneumocytes were measured on d 3 or after 3 mo. Single low-dose Printex 90 application induced no marked alterations in lung functions or BALF phospholipid levels but significant decrease in superoxide dismutase 2 and numerically elevated glutathione peroxidase 3 mRNA expression levels in type II pneumocytes. Multiple CBNP applications produced reduced lung function, collagen accumulation, elevated phospholipid levels in BALF, and a massive infiltration of macrophages. Type II pneumocyte mRNA expression of antioxidative enzymes remained unchanged throughout the subchronic experiment, but showed a significant decrease in interleukin (IL)-6Rα mRNA expression. This study demonstrates that an environmentally relevant CBNP concentration induced an acute inflammatory response, an effect that is exacerbated throughout the subchronic duration.