Solvothermal synthesis and characterisation of new one-dimensional indium and gallium sulphides: [C10N4H26]0.5[InS2] and [C10N4H26]0.5[GaS2]

Two new main group metal sulphides, [C₁₀N₄H₂₆]_0.5[InS₂] (1) and [C₁₀N₄H₂₆]_0.5[GaS₂] (2) have been prepared solvothermally in the presence of 1,4-bis(3-aminopropyl)piperazine and their crystal structures determined by single-crystal X-ray diffraction. Both compounds are isostructural and crystallise in the monoclinic space group P2₁/n (Z=4), with a=6.5628(5), b=11.2008(9), c=12.6611(9) Å and β=94.410(4)° (wR=0.035) for compound (1) and a=6.1094(5), b=11.2469(9), c=12.7064(10) Å and β=94.313(4)° (wR=0.021) for compound (2). The structure of [C₁₀N₄H₂₆]_0.5[MS₂] (M=In,Ga) consists of one-dimensional [MS₂]⁻ chains which run parallel to the crystallographic a axis and are separated by diprotonated amine molecules. These materials represent the first example of solvothermally prepared one-dimensional gallium and indium sulphides.     

g-C_3N_4/CaTi_2O_5复合材料制备及其光催化性能

利用类石墨氮化碳(g-C_3N_4)和亚稳相钙钛氧化物(CaTi_2O_5)固相法制备C_3N_4/CaTi_2O_5复合材料。利用X射线衍射(XRD)、金相显微镜、扫描电子显微镜(SEM)及附带能谱分析仪(EDS)和N2吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计(UV-Vis)测试了样品的光吸收性能,研究C_3N_4与CaTi_2O_5物质的量之比(nC_3N_4/nCaTi_2O_5)对C_3N_4/CaTi_2O_5复合样品的物相结构和微观形貌的影响,同时考察C_3N_4/CaTi_2O_5复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明:相比纯C_3N_4和CaTi_2O_5样品,C_3N_4/CaTi_2O_5复合样品在可见光下具有较高的光催化性能,随着nC_3N_4/nCaTi_2O_5增加,样品的光催化降解率随之增加而后降低,当nC_3N_4/nCaTi_2O_5=1∶1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

g-C3N4/CaTi2O5复合材料制备及其光催化性能

利用类石墨氮化碳（g-C₃N₄）和亚稳相钙钛氧化物（CaTi₂O₅）固相法制备C₃N₄/CaTi₂O₅复合材料。利用X射线衍射（XRD）、金相显微镜、扫描电子显微镜（SEM）及附带能谱分析仪（EDS）和N₂吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计（UV-Vis）测试了样品的光吸收性能,研究C₃N₄与CaTi₂O₅物质的量之比（n_C3N4/nCaTi₂O₅）对C₃N₄/CaTi₂O₅复合样品的物相结构和微观形貌的影响,同时考察C₃N₄/CaTi₂O₅复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明：相比纯C₃N₄和CaTi₂O₅样品,C₃N₄/CaTi₂O₅复合样品在可见光下具有较高的光催化性能,随着n_C3N4/nCaTi₂O₅增加,样品的光催化降解率随之增加而后降低,当n_C3N4/nCaTi₂O₅=1：1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

Preparation and photoluminescence properties of Mn-activated M2Si5N8 (M=Ca, Sr, Ba) phosphors

Mn²⁺-doped M₂Si₅N₈ (M=Ca, Sr, Ba) phosphors have been prepared by a solid-state reaction method at high temperature and their photoluminescence properties were investigated. The Mn²⁺-activated M₂Si₅N₈ phosphors exhibit narrow emission bands in the wavelength range of 500-700 nm with peak center at about 599, 606 and 567 nm for M=Ca, Sr, Ba, respectively, due to the ⁴T₁(⁴G)→⁶A₁(⁶S) transition of Mn²⁺. The long-wavelength emission of Mn²⁺ ion in the host of M₂Si₅N₈ is attributed to the effect of a strong crystal-field of Mn²⁺ in the nitrogen coordination environment. Also it is observed that there exists energy transfer between M₂Si₅N₈ host lattice and activator (Mn²⁺). The potential applications of these phosphors have been pointed out.     

Vibrational Spectra of the Cyclic SN-Compounds S4N4, S4N4H4 and S3N3Cl3

The IR and Raman spectra of solid and dissolved S₄N₄, S₄N₄H₄, S₄N₄D₄ and S₃N₃Cl₃ have been recorded and are assigned according to D_2d, C_4v and C_3v symmetry respectively. In the solid state, many forbidden bands and splittings of degenerate vibrations are observed because of the symmetry lowering in the crystals. Due to the different size and shape of the rings and to strong coupling of the normal modes there is no clear correlation between the SN ring stretching vibrations and the strength of the SN bonds, except for the one of the E modes. However, the stretching force constant show the trend expected from changes in interatomic distances.     

Neutron scattering study of the reorientational motions in Cr(CO)3(η6C6H6) and Mn(CO)3(η5C5H5)

Incoherent quasi-eleastic neutron scattering experiments: using different resolutions and a wide Q range, have been performed on polycrystalline samples of Cr(CO)₃(η⁶C₆H₆) and Mn(CO)₃(η⁵C₅H₅) in the 280–320 K temperature range. It is shown that aromatic rings are involved into a reorientational process characterized by an activation energy of ≈ 16 kJ mol^?1 and by correlation times of the order of 2 × 10^?11 s and 5 × 10^?11 s at 300 K for C₆H₆ and C₅H₅ rings respectively. Experimental elastic incoherent structure factors are in agreement with the 2π/6 and 2π/5 jump models and the fitted spectra confirm these models. From a comparison with heat-capacity results we conclude that M(CO)₃ groups are fixed during the reorientational process. Finally a comparison with literature data is presented.     

The study of Bi3B5O12: synthesis, crystal structure and thermal expansion of oxoborate Bi3B5O12

The paper presents a new data on the crystal structure, thermal expansion and IR spectra of Bi₃B₅O₁₂. The Bi₃B₅O₁₂ single crystals were grown from the melt of the same stoichiometry by Czochralski technique. The crystal structure of Bi₃B₅O₁₂ was refined in anisotropic approximation using single-crystal X-ray diffraction data. It is orthorhombic, Pnma, a=6.530(4), b=7.726(5), c=18.578(5) Å, V=937.2(5) Å³, Z=4, R=3.45%. Bi³⁺ atoms have irregular coordination polyhedra, Bi(1)O₆ (d(B-O)=2.09-2.75 Å) and Bi(2)O₇ (d(B-O)=2.108-2.804 Å). Taking into account the shortest bonds only, these polyhedra are considered here as trigonal Bi(1)O₃ (2.09-2.20 Å) and tetragonal Bi(2)O₄ (2.108-2.331 Å) irregular pyramids with Bi atoms in the tops of both pyramids. The BiO₄ polyhedra form zigzag chains along b-axis. These chains alternate with isolated anions [B₂^IVB₃^IIIO₁₁]⁷⁻ through the common oxygen atoms to form thick layers extended in ab plane. A perfect cleavage of the compound corresponds to these layers and an imperfect one is parallel to the Bi-O chains. The Bi₃B₅O₁₂ thermal expansion is sharply anisotropic (α₁₁≈α₂₂=12, α₃₃=3×10⁻⁶ °C⁻¹) likely due to a straightening of the flexible zigzag chains along b-axis and decreasing of their zigzag along c-axis. Thus the properties like cleavage and thermal expansion correlate to these chains.     

Hydrothermal synthesis and structural characterization of two organically templated zincophosphites with three-dimensional frameworks, (C6H14N2)·[Zn3(HPO3)4] and (C4H12N2)·[Zn3(HPO3)4]

Two organically templated zincophosphites, (C₆H₁₄N₂)·[Zn₃(HPO₃)₄] and (C₄H₁₄N₂)·[Zn₃(HPO₃)₄] have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction. (C₆H₁₄N₂)·[Zn₃(HPO₃)₄] crystallizes in the triclinic space group , with cell parameters, a=9.363(4) Å, b=10.051(4) Å, c=10.051(4) Å, α=85.777(13)°, β=82.091(9)°, and γ=79.783(9)°. (C₄H₁₄N₂)·[Zn₃(HPO₃)₄] crystallizes in the monoclinic space group P2₁/c, with cell parameters, a=9.9512(3) Å, b=10.1508(3) Å, c=17.8105(5) Å, and β=95.6510(10)°. Although the two structures are different, they have the same anionic framework compositions of [Zn₃(HPO₃)₄]²⁻. Their frameworks are built up from strictly alternating ZnO₄ tetrahedra and HPO₃ pseudo pyramids by sharing vertexes. There exist channels with an eight-membered ring window along the a- and c-axis. Powder X-ray diffraction, IR spectroscopy, ³¹P MAS solid-state NMR, thermogravimetric and differential thermal analyses were also carried out.     

The first quaternary lanthanide(III) nitride iodides: NaM4N2I7 (M=La-Nd)

In attempts to synthesize lanthanide(III) nitride iodides with the formula M₂NI₃ (M=La-Nd), moisture-sensitive single crystals of the first quaternary sodium lanthanide(III) nitride iodides NaM₄N₂I₇ (orthorhombic, Pna2₁; Z=4; a=1391-1401, b=1086-1094, c=1186-1211 pm) could be obtained. The dominating structural features are chains of trans-edge linked [NM₄]⁹⁺ tetrahedra, which run parallel to the polar 2₁-axis [001]. Between the chains, direct bonding via special iodide anions generates cages, in which isolated [NaI₆]^5- octahedra are embedded. The IR spectrum of NaLa₄N₂I₇ recorded from 100 to 1000 cm^-1 shows main bands at υ=337, 373 and 489 cm^-1. With decreasing radii of the lanthanide trications these bands, which can be assigned as an influence of the vibrations of the condensed [NM₄]⁹⁺ tetrahedra, are shifted toward higher frequencies for the NaM₄N₂I₇ series (M=La-Nd), following the lanthanide contraction.     

Study of M4,5N4,5N4,5 auger energy shifts of Cs and I in free CsI molecules

High-resolution electron beam excited M_4,5N_4,5N_4,5 Auger electron spectra of Cs and I have been measured from CsI vapour. The Auger energies of both Cs and I observed from gaseous CsI are higher than the corresponding free-atom energies due to extra-atomic relaxation. The molecular Auger results have been compared with corresponding photoelectron measurements and free-atom data. Estimates for extra-atomic relaxation energies have been extracted from the changes of the Auger parameter between molecular and atomic species and from the difference between experimental energies and energies calculated with a relativistic Dirac-Fock program, applying the point-charge model for the CsI molecule.     

Synthesis, structure and optical properties of new organic-inorganic haloplumbates complexes (C5H10N3)PbX4 (X=Br, Cl), (C2H2N4)PbBr3

Layered organic-inorganic composite materials (C₅H₁₀N₃)PbX₄ (X=Br 1, Cl 2) containing histaminium dications were grown via a solution-cooling process, and their structure and optical properties were determined. The organic ligand-histaminium introduced into the corner-sharing octahedra of the ‘PbX₄-layer’ contains both primary ammonium and imidazolium different from the traditionally primary amine found in this system. As comparison, another analogous amine of 3-amino-1,2,4-triazol was used as ligand to coordinate with PbBr₂ in acid solution. A novel complex (C₂H₂N₄)PbBr₃ (3) was obtained with zigzag PbBr₂ chains different from the PbX₄ layer in compound as 1 and 2. The hybrid (C₅H₁₀N₃)PbX₄ show exciton absorption at 339 nm for X=Cl and 419 nm for X=Br with the corresponding emission at 360 and 436 nm, respectively. The different PbBr₂ chain structure of compound 3 does not show photoluminescence.     

Energy analysis of metal-metal bonding in [RM-MR] (M = Zn, Cd, Hg; R = CH3, SiH3, GeH3, C5H5, C5Me5)

The metal-metal bonds of the title compounds have been investigated with the help of energy decomposition analysis at the DFT/TZ2P level. In good agreement with experiment, computations yield Hg-Hg bond distance in [H₃SiHg-HgSiH₃] of 2.706 Å and Zn-Zn bond distance in [(η⁵-C₅Me₅)Zn-Zn(η⁵-C₅Me₅)] of 2.281 Å. The Cd-Cd bond distances are longer than the Hg-Hg bond distances. Bond dissociation energies (-BDE) for Zn-Zn bonds in zincocene −70.6 kcal/mol in [(η⁵-C₅H₅)₂Zn₂] and −70.3 kcal/mol in [(η⁵-C₅Me₅)₂Zn₂] are greater amongst the compounds under study. In addition, [(η⁵-C₅H₅)₂M₂] is found to have a binding energy slightly larger than those in [(η⁵-C₅Me₅)₂M₂]. The trend of the M-M bond dissociation energy for the substituents R shows for metals the order GeH₃ < SiH₃ < CH₃ < C₅Me₅ < C₅H₅. Electrostatic forces between the metals are always attractive and they are strong (−75.8 to −110.5 kcal/mol). The results demonstrate clearly that the atomic partial charges cannot be taken as a measure of the electrostatic interactions between the atoms. The orbital interaction (covalent bonding) ΔE_orb is always smaller than the electrostatic attraction ΔE_elstat. The M-M bonding in [RM-M-R] (R = CH₃, SiH₃, GeH₃, C₅H₅, C₅Me₅; M = Zn, Cd, Hg) has more than half ionic character (56-64%). The values of Pauli repulsions, ΔE_Pauli, electrostatic interactions, ΔE_elstat, and orbital interactions, ΔE_elstat are larger for mercury compounds as compared to zinc and cadmium.     

Synthesis and Structure of a New Organic-Inorganic Framework with Tetranuclear Clusters, [Co4(OH)2(H2O)2](C4H11N2)2[C6H2(COO)4]2·3H2O

A new hybrid organic-inorganic three-dimensional compound, [Co₄(OH)₂(H₂O)₂](C₄H₁₁N₂)₂[C₆H₂(CO₂)₄]₂·3H₂O 1, has been synthesized via hydrothermal reactions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and magnetic techniques. Compound 1 crystallizes in the monoclinic space group P2₁/n (no. 14) with a=6.3029(9) Å, b=16.413(2) Å, c=17.139(2) Å, β=98.630(2)°, V=1735.0(4) ų, Z=2. Compound 1 contains tetranuclear Co₄(μ₃-OH)₂(H₂O)₂ clusters that are inter-linked by pyromellitate bridging ligands into a three-dimensional structure containing one-dimensional tunnels along the a-axis with water and pendant monoprotonated piperazine molecules in the center. The variable temperature magnetic susceptibility was measured from 2 to 300 K at 5000 Oe showing a predominantly anti-ferromagnetic interaction in 1, and the field dependence of magnetization was measured at 2, 5, 15, and 20 K indicating the competition of magnetic interactions in the tetranuclear centers.     

Molecular Complexes of Fullerenes C60 and C70 with Saturated Amines

New molecular complexes of fullerenes C₆₀ and C₇₀ with leuco crystal violet (LCV, 1-3); leucomalachite green (LMG, 4-6); crystal violet lactone (CVL, 7); N,N,N′,N′-tetrabenzyl-p-phenylenediamine (TBPDA, 8, and 9); N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPDA, 10, and 11); triphenylamine (TPA, 12, and 13); and substituted phenotellurazines (EPTA and TMPTA, 14, and 15) have been synthesized. Crystal structures have been solved for C₆₀ complexes with LMG (5, 6) TBPDA (8), TMPDA (10), and TPA (12). The C₆₀ molecules form closely packed double layers in 5 and 6, hexagonal layers in 10 and quasi-three-dimensional layers in 8 and 12. The substitution of disordered solvent molecules in the complexes with LMG (4, 5) by naphthalene ones results in the ordering of the C₆₀ molecules. According to IR-, UV-visible-NIR and ESR-spectroscopy the complexes have a neutral ground state. The spectra of 1-8, and 10 show intense charge transfer bands in the visible and NIR-range. On photoexcitation by white light (light-induced ESR (LESR) spectroscopy), 1 and 10 were shown to have an excited ionic state. The LESR signals were generated at light energies <2.25 eV indicating that the excited states in the complexes are realized mainly by direct charge transfer from donor to the C₆₀ molecule.     

Low-compressibility and hard material carbon nitride imide C2N2(NH): First principles calculations

First principles calculations are performed to investigate the structural, mechanical, and electronic properties of C₂N₂(NH). Our calculated lattice parameters are in good agreement with the experimental data and previous theoretical values. Orthorhombic C₂N₂(NH) phase is found to be mechanically stable at an ambient pressure. Based on the calculated bulk modulus and shear modulus of polycrystalline aggregate, C₂N₂(NH) can be regarded as a potential candidate of ultra-incompressible and hard material. Furthermore, the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli. Density of states and electronic localization function analysis show that the strong C-N covalent bond in CN₄ tetrahedron is the main driving force for the high bulk and shear moduli as well as small Poisson's ratio of C₂N₂(NH).     

Hydrothermal synthesis and structures of the novel niobium phosphates [NbOF(PO4)](N2C5H7) and [(Nb0.9V1.1)O2(PO4)2(H2PO4)](N2C2H10)

Two new niobium phosphates were synthesized and their crystal structures determined from single-crystal X-ray data. [NbOF(PO₄)](N₂C₅H₇) (1) (monoclinic, space group P2₁/c, a=11.442(1), b=9.1983(7), c=9.1696(8) Å, β=109.94(1)°) has a layered structure and is the first example of a negatively charged NbOF(PO₄) layer analogous to the MO(H₂O)PO₄ (M=V, Nb) layers. The layer charge is compensated by interlayer 4-aminopyridnium cations that adopt an unusual arrangement as a consequence of H-bonding and π-π interactions. The interlayer aminopyridnium cations can be exchanged with alkylammonium ions which form bilayers inclined at ∼65° to the NbOF(PO₄) layer. [(Nb_0.9V_1.1)O₂(PO₄)₂(H₂PO₄)] (N₂C₂H₁₀) (2) (orthorhombic, space group Pbca, a=15.821(2),b=9.0295(9),c=18.301(2) Å) has a disordered three-dimensional structure based on NbO(PO₄) layers cross-linked by phosphate tetrahedra, and has a similar structure to the known vanadium analog [V₂O₂(PO₄)₂(H₂PO₄)] (N₂C₂H₁₀).     

Zn(C3H3N2)2: a novel diamagnetic insulator

We have prepared polycrystalline samples of Zn(C₃H₃N₂)₂ by a liquid-mix technique. Characterization of the obtained samples has been performed with the aid of elemental, thermogravimetric, infrared spectra and X-ray powder diffraction analysis. We have measured electric permittivity (ε′, ε″), ac-conductivity (σ_ac), magnetic susceptibility (χ) and specific heat (C_p). The obtained data indicate that this material is a new diamagnetic insulator. A maximum around is found in C_pT⁻³, and it is suggested that in addition to the Debye lattice contribution, there exists a low-frequency mode assigned as an Einstein mode contribution to the total specific heat. As a main result of the study, we found ε′ to be constant in a wide temperature range and to have a small value of 2.3 at room temperature. This feature in combination with other properties like crystallization, good thermal stability (up to 400°C), weak moisture sensitivity and simple synthesis makes Zn(C₃H₃N₂)₂ to be a promising candidate for good insulating material in various applications.     

Synthesis, crystal structure and NLO property of a nonmetal pentaborate [C6H13N2][B5O6(OH)4]

A nonmetal pentaborate [C₆H₁₃N₂][B₅O₆(OH)₄] (1) has been synthesized by 1,4-diazabicyclo[2.2.2] octane (DABCO) and boric acid, and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system with space group Cc (no. 9), a=10.205(2) Å, b=14.143(3) Å, c=11.003(2) Å, β=113.97(3)°, V=1451.1(5) Å³, Z=4. The anionic units, [B₅O₆(OH)₄]⁻, are interlinked via hydrogen bonding to form a three-dimensional (3D) supramolecular network containing large channels, in which the protonated [C₆H₁₃N₂]⁺ cations are located. Second-harmonic generation (SHG) measurements on the powder samples reveal that 1 exhibits SHG efficiency approximately 0.9 times that of potassium dihydrogen phosphate (KDP).     

Structure and properties of ordered Li2IrO3 and Li2PtO3

The structures of Li₂MO₃ (M=Ir, Pt) can be derived from the well-known Li-ion battery cathode material, LiCoO₂, through ordering of Li⁺ and M⁴⁺ ions in the layers that are exclusively occupied by cobalt in LiCoO₂. The additional cation ordering lowers the symmetry from rhombohedral (R-3m) to monoclinic (C2/m). Unlike Li₂RuO₃ no evidence is found for a further distortion of the structure driven by formation of metal-metal bonds. Thermal analysis studies coupled with both ex-situ and in-situ X-ray diffraction measurements show that these compounds are stable up to temperatures approaching 1375 K in O₂, N₂, and air, but decompose at much lower temperatures in forming gas (5% H₂:95% N₂) due to reduction of the transition metal to its elemental form. Li₂IrO₃ undergoes a slightly more complicated decomposition in reducing atmospheres, which appears to involve loss of oxygen prior to collapse of the layered Li₂IrO₃ structure. Electrical measurements, UV-visible reflectance spectroscopy and electronic band structure calculations show that Li₂IrO₃ is metallic, while Li₂PtO₃ is a semiconductor, with a band gap of 2.3 eV.     

The structure of (C5H52W(CO)2 a compound containing a bent trihapto-cyclopentadienyl ligand

The crystal and molecular structure of the complex (C₅H₅)₂W(CO)₂ has been determined by X-ray analysis R₁ = 0.063). The structure contains a trihapto-cyclopentadienyl ligand, bent along its 1,3-axis by 20°. By this unusual structure, a 20-electron valence configuration of the central metal is avoided.