Orthorhombic Space Group Pbcn Research Articles

Synthesis, structural, impedance, optical, Mössbauer characterizations and magnetic studies of Pb-containing germanate compounds

The orthorhombic antiferromagnetic germanate minerals Pb2Fe2Ge2O9 and Pb2Mn2Ge2O9 have been prepared via solid state reaction procedure. An extensive study of structural, dielectric, optical and magnetic properties of both the germanates have been investigated by employing different measurements such as X-ray diffraction, FTIR, SEM, impedance, UV–Vis–NIR & Mössbauer spectroscopic and magnetometary. Rietveld refinement of room temperature XRD patterns revealed that both the compounds crystallize in the orthorhombic space group Pbcn. FTIR spectrum exhibits the presence of M−O & Ge–O bonds which confirms strong chemical bonding. Morphological analysis through SEM showed good crystallinity of both the samples. The variation of dielectric constant, loss tangent and impedance with frequency have been studied and it has been established that both the germanates are semiconducting at 300K (RT) which may be attributed to the stacking of ions at grain boundaries. The optical band gaps estimated by UV–Vis–NIR spectroscopic measurements further confirms the semiconducting nature of the prepared germanates. 57Fe Mössbauer spectroscopic measurement on synthesized Pb2Fe2Ge2O9 sample was carried out at RT. The obtained values of IS and QS showed that iron is in Fe3+ high spin state (t2g3eg2,s=5/2) and occupy two different sites, Fe1 and Fe2. The field dependent magnetization measurements show that both the compounds display dominant paramagnetic nature at 300K. The temperature dependent magnetization data reveal very sharp first order type AFM to PM transition at TN ∼50K and TN ∼8K for Pb2Fe2Ge2O9 and Pb2Mn2Ge2O9, respectively, and weak FM nature below Neel temperature. The field dependent properties of both the compounds have been analyzed by drawing the M versus H plots at low and room temperatures. The values of calculated effective magnetic moment 6.07μB and 3.95μB for Fe3+ and Mn3+ ions are in the high spin states (t2g3eg2,s=5/2 and )t2g3eg1,s=2.

La4Ga2S8O3: A Rare-Earth Gallium Oxysulfide with Disulfide Ions.

Band gap engineering using multiple anions is an established approach to novel photocatalysts that exhibit suitable band gap energies for water splitting and high photocorrosion resistance. However, few studies have been conducted on photocatalysts with polyanions, including polychalcogenide ions. Here, we present a new quaternary gallium oxysulfide with disulfide pairs (S2)2-, La4Ga2S8O3, grown out of a KI molten salt. Single-crystal X-ray diffraction analysis revealed that the oxysulfide crystallizes in the orthorhombic space group Pbcn with lattice constants of a = 18.3330(6) Å, b = 13.0590(5) Å, and c = 5.9022(3) Å. In the crystal structure, the GaS4-based zigzag chains and OLa4-based fluorite-like strips are independently arranged in two dimensions, which alternately stack via the disulfide pairs along the third direction. The oxysulfide is a direct-type semiconductor with a band gap of 2.45 eV. First-principles calculations combined with X-ray photoemission spectroscopy measurements show that S 3p states derived from the disulfide pairs dominate the valence band maximum and conduction band minimum, and these band-edge positions are suitable for the oxidation and reduction of water. Our comprehensive study based on the electronic structure suggests that the disulfide pairs make La4Ga2S8O3 a potential photocatalyst for water splitting under visible-light irradiation.

Preparation, Characterization of Some Lanthanide(III) Complexes of N'-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide

The present investigation describes the synthesis and structural study of the ligand N'-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide (HL), which was used to generate two type complexes formulated as [Ln(HL)2(NO3)2(H2O)].(NO3) (Ln = La (1) and Pr (2)) and [Ln(HL)2(NO3)(H2O)2].(NO3)2 (Ln = Nd (3), Sm (4), Gd (5) and Tb (6)). The ligand and the complexes are characterized by NMR, UV-Visible and FTIR spectroscopies, conductivity measurements and room temperature magnetic moment measurements. The [La(HL)2(NO3)2(H2O)].(NO3) compound crystallizes in the orthorhombic space group Pbcn with the following unit cell parameters: a = 16.8634(8) Å, b = 8.0615(4) Å, c = 30.2833(15) Å, V = 4116.8(3) Å3, Z = 8, R1 = 0.049 and wR2 = 0.120. The structure reveals that two neutral ligand molecules in η3-mode, two bidentate nitrate groups in η2-mode and one water molecule coordinate the central La3+. Each organic molecules acts through one carbonyl oxygen atom, one azomethine nitrogen atom and one nitrogen atom from a pyridine ring. The lanthanide ion has a coordination number of 11 and the coordination environment can be described as distorted pentacapped trigonal prism. Numerous hydrogen bonds link the molecules into three-dimensional network.

Structure-directing role of CH⋯X (X = C, N, S, Cl) interactions in three ionic cobalt complexes: X-ray investigation and DFT study using QTAIM Vr predictor to eliminate the effect of pure Coulombic forces.

Three cobalt complexes, namely [CoIII(HL1)2(N3)2]ClO4 (1), [CoIII(L2)(HL2)(N3)]ClO4·1.5H2O (2), and [CoIII(L3)(HL3)(NCS)]2 [CoIICl2(NCS)2] (3), where HL1 = 2-(3-(dimethylamino)propyliminomethyl)-6-methoxyphenol, HL2 = 2-(2-(dimethylamino)ethyliminomethyl)-4,6-dichlorophenol, and HL3 = 2-(2-(dimethylamino)ethyliminomethyl)-6-methoxyphenol, as potential tridentate N2O-donor Schiff base ligands, were synthesized and characterized using elemental analysis, IR and UV-vis spectroscopy, and single-crystal X-ray diffraction studies. All three were found to be monomeric ionic complexes. Complex 1 crystallizes in the orthorhombic space group Pbcn, whereas both complexes 2 and 3 crystallize in triclinic space groups, P1̄. Further, 1 and 2 are cationic complexes of octahedral cobalt(iii) with perchlorate anions, whereas complex 3 contains a cationic part of octahedral cobalt(iii) and an anionic part of tetrahedral cobalt(ii). Hydrogen-bonding interactions involving aromatic and aliphatic CH bonds as H-bond donors and the pseudo-halide co-ligands as H-bond acceptors were established, which are important aspects governing the X-ray packing. These interactions were analyzed theoretically using the quantum theory of atoms in molecules (QTAIM) and non-covalent interaction plot (NCI plot) analyses. Moreover, energy decomposition analysis (EDA) was performed to analyze the stabilization of the complexes in terms of the electrostatic, dispersion, and correlation forces.

High-pressure synthesis and crystal structure determination of Tb2SiB2O8

Abstract We report the high-pressure/high-temperature synthesis (11 GPa, 1300 °C) of the new compound Tb2SiB2O8. This rare earth borosilicate crystallizes in the orthorhombic space group Pbcn (no. 60) with the unit cell parameters a = 13.2480(3), b = 4.3904(1), and c = 9.1611(3) Å. It is built up of corner-sharing [BO4] tetrahedra forming infinite chains, that are connected to layers via [SiO4] tetrahedra. The layers are connected via [TbO7] polyhedra.

Luminescence and Scintillation in the Niobium Doped Oxyfluoride Rb4Ge5O9F6:Nb

A new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.98430(10) Å, b = 11.7265(2) Å, and c = 19.2732(3) Å, consisting of germanium oxyfluoride layers made up of Ge3O9 units connected by GeO3F3 octahedra. In its pure form, Rb4Ge5O9F6 shows neither luminescence nor scintillation but when doped with niobium, Rb4Ge5O9F6:Nb exhibits bright blue luminescence and scintillation. The isostructural doped structure, Rb4Ge5O9F6:Nb, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.9960(3) Å, b = 11.7464(6) Å, and c = 19.3341(9) Å. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements suggest that the niobium is located in an octahedral coordination environment. Optical measurements inform us that the niobium dopant acts as the activator. The synthesis, structure, and optical properties are reported, including radioluminescence (RL) measurements under X-ray irradiation.

Diradicals or Zwitterions: The Chemical States of m -Benzoquinone and Structural Variation after Storage of Li Ions

Diradicals or Zwitterions: The Chemical States of <i>m</i> -Benzoquinone and Structural Variation after Storage of Li Ions

Group II complexes of N- and O-donors Mixed-ligands as anticancer agents

Reactions of 1,10-phenanthroline (phen), p-amino benzoic acid (paba) and cinnamic acid (cina) with MCO3 (M = Mg, Ca, Sr) yielded two mononuclear magnesium complexes [{Mg(phen)(H2O)4}(phen)(paba)2] (1) and [{Mg(phen)(H2O)4}(phen)(cina)2] (2) and two one dimensional chains of both calcium and strontium [Ca(phen)(cina)]n (3), and [Sr(phen)(cina)]n (4) respectively. The structures were characterized by a variety of analytical techniques including IR, UV–Vis, 1H NMR, elemental analysis, and single crystal X–ray diffraction analysis. In these complexes, phen binds via an N,Ń–chelate pocket, while the monoanionic paba—/cina— ligands either remains uncoordinated (in case of 1 and 2) or coordinated in a tridentate fashion (in case of 3 and 4). Complexes 1, 3 and 4 crystallize in the same orthorhombic space group Pbcn while complex 2 crystallizes in triclinic space group P1. In complex 1 and 2, Mg2+ cation adopts a distorted six-coordinate octahedral geometry comprising an [N2O4] donor set while in complexes 3 and 4, Ca2+ and Sr2+ cations adopt a distorted eight-coordinate geometry comprising [N2O6] donor sets. Complexes 1, 2 and 4 were found to be potent anticancer against oral cancer cell line i.e. CAL-27 with IC50 1.85 ± 0.11 , 2.98 ± 1.2 and 5.05 ± 0.35 respectively while complex 3 was inactive.

Variable Structures and One-Dimensional-Canting Antiferromagetism Found in Fluoride Selenates, A2Mn(SeO4)F3 (A = K, Rb, Cs).

Three new alkali-metal manganese fluoride selenates, A2Mn(SeO4)F3 (A = K, Rb, Cs), were prepared through hydrothermal redox reactions. The products consisted of one-dimensional polymeric anionic ∞[Mn(SeO4)F3]2- chains, where the A+ cations are connected by O and/or F atoms to form blocks with two-dimensional layers. A2Mn(SeO4)F3 (A= Rb, Cs) is isostructural with the monoclinic space group P21/c, while K2Mn(SeO4)F3 crystallizes in the orthorhombic space group Pbcn. A2Mn(SeO4)F3 (A = K, Rb, Cs) forms spin chains of Mn3+ with different Mn-F-Mn bridges, which showed canting antiferromagnetic behaviors. Single-crystal magnetic measurements revealed that the magnetic moments of the Mn ions were more canted for larger alkali-metal compounds in an antiferromagnetically ordered state.

Four coordination polymers based on 5-(3,5-dicarboxybenzyloxy) isophthalic acid: Synthesis, structures, photocatalytic properties, fluorescence sensing and magnetic properties

Four coordination polymers named [Co(L)0.5(bib)]n(1), Zn(H2L)(bib)]·2H2O}n(2), Cd(L)0.5(1,2-bimb)]n(3) and Zn(L)0.5(bib)]n(4) (H4L ​= ​5-(3,5-dicarboxybenzyloxy) isophthalic acid, bib ​= ​1,4-bis(1-imidazolyl)benzene, and 1,2-bimb ​= ​1,2-bis(1-imidazolylmethyl)benzene) were synthesized by solvothermal method and structurally characterized by means of single-crystal X-ray diffraction, infrared spectra and elemental analyses. Complex 1 crystallized in orthorhombic space group Pbcn had a 2-fold interpenetrated framework. Complex 2 showed a 4-fold interpenetrated framework. Complex 3 presented a 3-fold interpenetrated framework that crystallized in the triclinic system Pī space group. Complex 4 was a three-dimensional (3D) porous framework. Remarkably, the photocatalytic degradation experiments of complexes 1–4 on methylene blue (MB) indicated that these complexes 1–4 exhibited obvious degradation effect on MB. Moreover, the investigation of the luminescent properties of complexes 2–4 revealed that these complexes 2–4 could be served as a potential highly selective Fe3+ ion luminescent sensor. In addition, the magnetic analyses of complex 1 indicated that there was antiferromagnetic interaction between the Co (II) ions in complex 1.

Synthesis Crystal Structure and Spectral Properties of New Sulfonamides

In this paper, we report new sulfonamide derivatives, 4-((2,4-dichlorophenylsulfonamido)methyl)cyclohexanecarboxylic acid (1), ethyl 4-((naphthalene-2-sulfonamido)methyl)cyclohexanecarboxylate (2), and ethyl 4-((2,5-dichlorophenylsulfonamido)methyl)cyclohexanecarboxylate (3). The compounds were and characterized by FTIR, ESI-MS, and X-ray crystallography. Single crystal X-ray diffraction analysis shows that 1 crystallizes in the orthorhombic space group Pbcn, 2 in the monoclinic space group Cc and 3 in the monoclinic space group Cc. All three molecules feature hydrogen bonding. Three sulfonamide derivatives, 4-((2,4-dichlorophenylsulfonamido)methyl)cyclohexanecarboxylic acid (1), ethyl 4-((naphthalene-2-sulfonamido)methyl)cyclohexanecarboxylate (2) and ethyl 4-((2,5-dichlorophenylsulfonamido) methyl)cyclo-hexanecarboxylate (3) have been synthesized and their structures confirmed by single crystal X-ray diffraction. Hydrogen bonding in compound 1 involves carboxylic groups and N–H moieties as well as non-classical C–H···O interactions, while in 2 and 3, the N–H moiety and an oxygen atom of the sulfonamide functional group of neighboring molecules are involved.

Coordination behavior of dinuclear silver complex of sulfamethoxazole with solvent molecule having static rotational disorder: Spectroscopic characterization, crystal structure, Hirshfeld surface and antimicrobial activity

The static rotational disorder in ‘humanoid’ silver complex of sulfamethoxazole (smx) was synthesized and characterized by elemental, infrared, NMR spectroscopy and for analysis of structure function relation, crystalline powder further crystallized in β-picoline solvent. The SC-XRD data suggest that asymmetric unit [Ag2(C10H10N3O3S)2(C5H5N)] crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 27.4252(19)Å, b = 16.1656(15)Å, c = 14.1467(13)Å and Z = 8. The structure is unusual, β-picoline rings have identical static rotational disorder, both the sides of β-picoline is appearing 53% and 47% occupancy in the structure; bond (Ag2-N7) is rotated exactly 1800 to create like ‘humanoid’ geometry, The Ag1 is located in planner T-shape fashion with bond angle [N1-Ag1-N5 = 177.3(4)] and Ag2 is located in distorted square planner fashion with geometric index τ4 = 0.27, both argentophilic interaction Ag1-Ag2 are separated with 2.94(14) Å distance. Interestingly, disorder solvate molecules are taking part in structure stability via C-H…O, C-H…π and Ag…π intra and inter molecular interactions. The qualitative and quantitative contribution of disorder was analyzed using Hirshfeld surface (HF) and 2D fingerprint plots analysis. From HF, large Van der Waals or highly active (donor or acceptor) sites are covered by disordered ring on dnorm surface. The contribution of H…H contacts in presence of HUM-1 and HUM-2 is 37.4% and 39.8% respectively. Biological response against Gram(+ve) and Gram(-ve) bacteria strain in the range of 204 – 128 μg/mL are carried for free ligand and its metal complex.

Improving LED Efficiency with the New Polymorph β-Ca1-x Srx AlSiN3 :Eu2.

Innovative materials for phosphor-converted white light-emitting diodes (pc-LEDs) are much sought after due to the huge potential of the LED technology to reduce energy consumption worldwide. One of the main levers for further improvements are the conversion phosphors. The system Ca1-x Srx AlSiN3 :Eu2+ currently provides one of the most important red-emitting phosphors for pc-LEDs. We report the discovery of the new polymorph β-Ca1-x Srx AlSiN3 :Eu2+ which allows for significant improvements to LED efficacies. It crystallizes in the orthorhombic space group Pbcn with lattice parameters a=982.43(10) pm, b=575.2(1) pm and c=516.12(5) pm. Compared to α-Ca1-x Srx AlSiN3 :Eu2+ , its emission shows a significantly reduced spectral full-width at half maximum (FWHM). With that, we demonstrated 3 % efficacy increase for white light-emitting pc-LEDs. The new polymorph can easily be industrialised, because the synthesis works on the same equipment as α-Ca1-x Srx AlSiN3 :Eu2+ .

Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4

A novel imidazolium halometallate molten salt with formula (trimim)[FeCl4] (trimim: 1,2,3-trimethylimidazolium) was synthetized and studied with structural and physico-chemical characterization. Variable-temperature synchrotron X-ray powder diffraction (SXPD) from 100 to 400 K revealed two structural transitions at 200 and 300 K. Three different crystal structures were determined combining single crystal X-ray diffraction (SCXD), neutron powder diffraction (NPD), and SXPD. From 100 to 200 K, the compound exhibits a monoclinic crystal structure with space group P21/c. At 200 K, the former crystal system and space group are retained, but a disorder in the organic cations is introduced. Above 300 K, the structure transits to the orthorhombic space group Pbcn, retaining the crystallinity up to 400 K. The study of the thermal expansion process in this temperature range showed anisotropically evolving cell parameters with an axial negative thermal expansion. Such an induction occurs immediately after the crystal phase transition due to the translational and reorientational dynamic displacements of the imidazolium cation within the crystal building. Electrochemical impedance spectroscopy (EIS) demonstrated that this motion implies a high and stable solid-state ionic conduction (range from 4 × 10−6 S cm−1 at room temperature to 5.5 × 10−5 S cm−1 at 400 K). In addition, magnetization and heat capacity measurements proved the presence of a three-dimensional antiferromagnetic ordering below 3 K. The magnetic structure, determined by neutron powder diffraction, corresponds to ferromagnetic chains along the a-axis, which are antiferromagnetically coupled to the nearest neighboring chains through an intricate network of superexchange pathways, in agreement with the magnetometry measurements.

High-Spin and Incomplete Spin-Crossover Polymorphs in Doubly Chelated [Ni(L)2Br2] (L = tert-Butyl 5-Phenyl-2-pyridyl Nitroxide).

Complexation of nickel(II) bromide with tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO) gave two morphs of doubly chelated [Ni(phpyNO)2Br2] as a 2p-3d-2p heterospin triad. The α phase crystallizes in the orthorhombic space group Pbcn. An asymmetric unit involves a half-molecule. The torsion angle around Ni-O-N-C2py is as small as 6.5(3)° at 100 K and 7.0(6)° at 400 K, guaranteeing an orthogonal arrangement between the magnetic radical π* and metal 3dx2-y2 and 3dz2 orbitals. Magnetic study revealed the high-spin ground state with the exchange coupling constant 2J/kB = +288(5) K, on the basis of a symmetrical spin Hamiltonian. The β phase crystallizes in the monoclinic space group P21/n. The whole molecule is an independent unit. The Ni-O-N-C2py torsion angles are 24.2(6) and 37.2(5)° at 100 K and 10.4(7) and 25.9(6)° at 400 K. A magnetic study revealed a very gradual and nonhysteretic spin transition. An analysis based on the van't Hoff equation gave a successful fit with the spin-crossover temperature of 134(1) K, although the susceptibility did not reach the theoretical high-spin value at 400 K. Density functional theory calculation on the β phase showed ground Stotal = 0 in the low-temperature structure while Stotal = 2 in the high-temperature structure, supporting the synchronized exchange coupling switch on both sides. Consequently, the β phase can be recognized as an "incomplete spin crossover" material, as a result of conflicting thermal depopulation effects in a high-temperature region.

Synthesis, structure and characterization of a new triphosphate: CsMg2P3O10

A new phosphate crystal CsMg2P3O10 was grown by molten salt method. The single-crystal X-ray diffraction analysis reveals that this compound crystallizes in orthorhombic space group Pbcn (No.60) with unit cell parameters a = 7.8757(8) Å, b = 8.6902(9) Å and c = 13.7235(14) Å, V = 939.26(17) Å3. In the structure, the basic building units are the [P3O10]5- trimers consisted of three PO4 tetrahedra shared the corner oxygen atoms, and the [Mg2O8] dimers composed of two MgO5 hexahedrons linked through edge-sharing. The structure exhibits a novel three-dimensional network, constructed by the [Mg2O8] dimers and [P3O10]5- trimers, where the Cs+ ions reside in the cavities. Furthermore, some related tests and first-principle calculations were employed for the compound characterization.

Synthesis, structure and bioactivity of Ni2+ and Cu2+ acylhydrazone complexes.

Two acylhydrazone complexes, bis{6-methyl-N'-[1-(pyrazin-2-yl-κN1)ethylidene]nicotinohydrazidato-κ2N',O}nickel(II), [Ni(C13H12N5O)2], (I), and di-μ-azido-κ4N1:N1-bis({6-methyl-N'-[1-(pyrazin-2-yl-κN1)ethylidene]nicotinohydrazidato-κ2N',O}nickel(II)), [Cu2(C13H12N5O)2(N3)2], (II), derived from 6-methyl-N'-[1-(pyrazin-2-yl)ethylidene]nicotinohydrazide (HL) and azide salts, have been synthesized. HL acts as an N,N',O-tridentate ligand in both complexes. Complex (I) crystallizes in the orthorhombic space group Pbcn and has a mononuclear structure, the azide co-ligand is not involved in crystallization and the Ni2+ centre lies in a distorted {N4O2} octahedral coordination environment. Complex (II) crystallizes in the triclinic space group P-1 and is a centrosymmetric binuclear complex with a crystallographically independent Cu2+ centre coordinating to three donor atoms from the deprotonated L- ligand and to two N atoms belonging to two bridging azide anions. The two- and one-dimensional supramolecular structures are constructed by hydrogen-bonding interactions in (I) and (II), respectively. The in vitro urease inhibitory evaluation revealed that complex (II) showed a better inhibitory activity, with the IC50 value being 1.32±0.4 µM. Both complexes can effectively bind to bovine serum albumin (BSA) by 1:1 binding, which was assessed via tryptophan emission-quenching measurements. The bioactivities of the two complexes towards jack bean urease were also studied by molecular docking. The effects of the metal ions and the coordination environments in the two complexes on in vitro urease inhibitory activity are preliminarily discussed.

Synthesis, crystallographic structure, theoretical calculations, spectral and thermal properties of trans-diaquabis(trans-4-aminoantipyrine)cobalt(II) acesulfamate

A new acesulfame derivative compound, trans-diaquabis(trans-4-aminoantipyrine)cobalt(II) acesulfamate that formulated as (C30H38CoN8O12S2) was synthesized and characterized by X-ray diffraction method, FT-IR, UV–Vis techniques and Thermal analysis. The compound crystallizes in the orthorhombic space group Pbcn with parameters a = 28.0156 (10) Å, b = 9.4273 (4) Å, c = 13.7777 (5) Å, α = β = γ = 90°, Z = 4. Theoretical calculations have been carried out by using Density Functional Theory (DFT) method in the ground state. With a successful optimization, Mulliken population method, molecular electrostatic potential (MEP) and frontier molecular orbitals were calculated. In addition, the thermal behavior of the complex was investigated. Hirshfeld surface analyses (dnorm surfaces and two-dimensional fingerprint plots) which reveal the nature of intermolecular interactions for the title compound were performed and discussed. The Hirshfeld surface analysis of the crystal structure specifies that the most important contributions for the crystal packing are from O⋯H/H⋯O (37.1%), H⋯H (33.5%) and C⋯H/H⋯C (16.5%) interactions.

Synthesis and Characterization of [Br3 ][MF6 ] (M=Sb, Ir), as well as Quantum Chemical Study of [Br3 ]+ Structure, Chemical Bonding, and Relativistic Effects Compared with [XBr2 ]+ (X=Br, I, At, Ts) and [TsZ2 ]+ (Z=F, Cl, Br, I, At, Ts).

[Br3 ][SbF6 ] and [Br3 ][IrF6 ] were synthesized by interaction of BrF3 with Sb2 O3 or iridium metal, respectively. The former compound crystallizes in the orthorhombic space group Pbcn (No. 60) with a=11.9269(7), b=11.5370(7), c=12.0640(6) Å, V=1660.01(16) Å3 , Z=8 at 100 K. The latter compound crystallizes in the triclinic space group P (No. 2) with a=5.4686(5), b=7.6861(8), c=9.9830(9) Å, α=85.320(8), β=82.060(7), γ=78.466(7)°, V=406.56(7) Å3 , Z=2 at 100 K. Both compounds contain the cation [Br3 ]+ , which has a bent structure and is coordinated by octahedron-like anions [MF6 ]- (M=Sb, Ir). Experimentally obtained cell parameters, bond lengths, and angles are confirmed by solid-state DFT calculations, which differ from the experimental values by less than 2 %. Relativistic effects on the structure of the tribromonium(1+) cation are studied computationally and found to be small. For the heaviest analogues containing At and Ts, however, pronounced relativistic effects are found, which lead to a linear structure of the polyhalogen cation.

Syntheses, structures, anomalous phase transition and optical properties of two new polymorphic α- and β-LiMoPO6.

New polymorphous phases, α- and β-LiMoPO6, have been successfully synthesized by the high temperature solution technique and their structures have been determined by single crystal X-ray diffraction. α-LiMoPO6 crystallizes in the orthorhombic space group Pbcn (No. 60) with a = 12.1141(4) Å, b = 8.9251(3) Å and c = 8.7389(3) Å, while β-LiMoPO6 crystallizes in the monoclinic space group P21/c (No. 14) with a = 6.3441(3) Å, b = 7.5949(3) Å, c = 9.3430(4) Å and β = 94.546(4)°. Both structures exhibit a similar three-dimensional (3D) framework composed of MoO6 octahedra and PO4 tetrahedra. Interestingly, an anomalous phase transition, i.e. the high-temperature β-LiMoPO6 phase exhibiting larger density than the low-temperature α-LiMoPO6, has been observed. Detailed structural analyses show that the anomalous phase transition mainly originates from the 'straightened' effect of the zigzag [MoO3O3PO]∞ chains in their structures. Furthermore, the optical and thermal properties of two compounds are also reported.