Synthesis,crystal structure and optical properties of the new tantalum polysulfide Rb6Ta4S25 and its thermal degradation to Rb6Ta4S22

The reaction of Rb₂S₃, Ta and S at 723 K yields red–orange crystals of the new ternary compound Rb₆Ta₄S₂₅. It crystallizes in the monoclinic space group C2/c (No. 15) with a=36.943(2), b=8.1028(3), c=12.6415 (8) Å, β=98.858 (7)°, V=3739.0(4) ų and Z=4. In the crystal structure two Ta₂S₁₁ units are connected by a S₃ chain forming the [Ta₄S₂₅]⁶⁻ anion. Each Ta⁵⁺ ion is surrounded by seven sulfur ions forming a strongly distorted pentagonal bipyramid. The coordination mode around the Ta⁵⁺ centers may be formulated as [(Ta₂(μ₂-η²,η¹-S₂)₃(η²-S₂)(S)₂)₂(μ₂-η¹,η¹-S₅)]⁶⁻. The anions are stacked parallel to the crystallographic b axis and are separated by the Rb⁺ ions. With UV–Vis spectroscopic investigations the optical band gap of 2.35 eV was determined. Measurements using differential-scanning calorimetry show an irreversible loss of three sulfur atoms at 681 K leading to the formation of Rb₆Ta₄S₂₂.     

Synthesis,crystal structure and optical properties of A3Zr2P5S18 (A=Rb,Cs): the first quaternary zirconium thiophosphates

The first quaternary zirconium thiophosphates Rb₃Zr₂P₅S₁₈ (1) and Cs₃Zr₂P₅S₁₈ (2) were synthesized by reacting ZrS₂ with an in situ formed melt of A₂S₃ (A=Rb, Cs), P₂S₅ and S. The compounds are isostructural and crystallize in the monoclinic space group Cc with Z=4. Compound 1 has cell parameters a=9.248(2) Å, b=9.860(2) Å, c=33.622(7) Å and β=94.73(3)° and compound 2 a=9.288(2) Å, b=9.956(2) Å, c=34.061(7) Å and β=94.26(3)°. The structures are composed of a two-dimensional anionic layer [Zr₂P₅S₁₈]³⁻ and intervening alkali cations. Each of the two independent Zr atoms is surrounded by seven S atoms yielding a distorted pentagonal bipyramid. The ZrS₇ polyhedra are interconnected into the final layered anion by [P₂S₇] groups which act in an unusual edge- and corner-sharing mode and by edge-sharing [PS₄] tetrahedra. Compound 2 was characterized with MIR and UV/vis diffuse reflectance spectroscopy.     

S K and P K absorption spectra and electronic structures of layered thiophosphates MPS3

The S K and P K absorption spectra of layered thiophosphates MPS₃ (M = Mg, Mn, Fe, Ni, Zn, Cd, Sn) were measured. The general features of the S K absorption spectra resemble one another, but the intensity ratio of the first peak to a higher energy structure and the energy position of a shoulder vary, depending on the metal species. All the P K absorption spectra exhibit a prominent peak in the neighborhood of the threshold. It is found that (1) the spectra mainly reveal the p-like partial density of states of the unoccupied energy levels of a [P₂S₆]^4- cluster and (2) the first peak arises predominantly from the electronic transitions to the antibonding levels of the PS bonds. The electronic structures and the optical spectra are discussed.     

Synthesis and characterization of two quaternary thorium chalcophosphates: Cs4Th2P6S18 and Rb7Th2P6Se21

Two new thorium chalcophosphates have been synthesized by the reactive flux method and characterized by single-crystal X-ray diffraction, diffuse reflectance, and Raman spectroscopy: Cs4Th2P6S18 (I); Rb7Th2P6Se21 (II). Compound I crystallizes as colorless blocks in the triclinic space group P1 (No. 2) with a = 12.303(4) A, b = 12.471(4) A, c = 12.541(4) A, alpha = 114.607(8) degrees, beta = 102.547(6) degrees, gamma = 99.889(7) degrees, and Z = 2. The structure consists of (Th2P6S18)(4-) layers separated by layers of cesium cations and only contains the (P2S6)(4-) building block. Compound II crystallizes as red blocks in the triclinic space group P1 (No. 2) with a = 11.531(3) A, b = 12.359(4) A, c = 16.161(5) A, alpha = 87.289(6) degrees, beta = 75.903(6) degrees, gamma = 88.041(6) degrees, and Z = 2. The structure consists of linear chains of (Th2P6Se21)(7-) separated by rubidium cations. Compound II contains both the (PSe4)(3-) and (P2Se6)(4-) building blocks. Both structures may be derived from two known rare earth structures where a rare earth site is replaced by an alkali or actinide metal to form these novel structures. Optical band gap measurements show that compound I has a band gap of 2.8 eV and compound II has a band gap of 2.0 eV. Solid-state Raman spectroscopy of compound I shows the vibrations expected for the (P2S6)(4-) unit. Raman spectroscopy of compound II shows the vibrations expected for both (PSe4)(3-) and (P2Se6)(4-) units. Our work shows the remarkable diversity of the actinide chalcophosphate system and demonstrates the phase space is still ripe to discover new structures.     

Synthesis, crystal and band structures, and optical properties of a new quaternary metal pnictidehalide: (Hg2Cd2As2Br)Br

A new quaternary cadmium and mercury pnictidehalide semiconductor (Hg2Cd2As2Br)Br (1) has been prepared by the solid-state reaction of HgBr2 with elemental Cd and As at 420 degrees C. Compound 1 crystallizes in the space group Pmma of the orthorhombic system with two formula units in a cell: a = 8.791(4) A, b = 4.701(2) A, c = 9.779(6) A, V = 404.2(3) A(3). The structure of 1 is composed of parallel slabs bridged by linearly coordinated Hg atoms to form a 3D cationic network with the channels occupied by discrete Br anions, in which the layer consists of interlinks of linear (HgAs2Br2) tetrahedral chains and (CdAs2Br) trigonal chains. The optical properties were investigated in terms of the diffuse reflectance and Fourier transform infrared spectra. The electronic band structure along with the density of states (DOS) calculated by the DFT method indicate that compound 1 is a semiconductor with an indirect band gap and that the optical absorption mainly originates from the charge transitions from the Br2-4p and As-4p to Cd-5s and Hg-6s states.     

Synthesis,crystal structures and electrochemical properties of two new metal-centered ferrocene complexes

Two new metal-centered ferrocene complexes Ni(SCN)2(L)4 (1) and Cu(OAc)2(L)2 (2) (L = 1-[1-ferro- cenylmethyl]imidazole) have been synthesized and characterized by elemental analysis, single crystal X-ray diffraction analysis, spectroscopic and cyclic voltammetric measurements. The geometry of Ni(Ⅱ) in 1 is octahedral, with four ligands in the equatorial plan and two thiocyanate anions at the axial site, while that of Cu(Ⅱ) in 2 is a distorted octahedron formed by two chealted OAc- and two ligands. Single c...     

Synthesis, crystal structure and magnetic properties of the new one-dimensional manganate Cs3Mn2O4

Cs(3)Mn(2)O(4), a new member of the small family of ternary manganese (II/III) mixed-valent compounds, has been synthesized via the azide/nitrate route and studied using powder and single crystal X-ray diffraction, magnetic susceptibility measurements and density functional theory (DFT). Its crystal structure (P2(1)/c, Z = 8, a = 1276.33(1) pm, b = 1082.31(2) pm, c = 1280.29(2) pm, β = 118.390(2)°) is based on one-dimensional MnO(2)(1.5-) chains built up from edge-sharing MnO(4) tetrahedra. The title compound is the first example of an intrinsically doped transition metalate of the series A(x)MnO(2), (A = alkali metal) where a complete 1:1 charge ordering of Mn(2+) and Mn(3+) is observed along the chains (-Mn(2+)-Mn(3+)-Mn(2+)-Mn(3+)-). From the magnetic point of view it basically consists of ferrimagnetic MnO(2) chains, where the Mn(2+) and Mn(3+) ions are strongly antiferromagnetically coupled up to high temperatures. Very interestingly, their long-range three-dimensional ordering below the Néel temperature (T(N)) ~12 K give rise to conspicuous field dependent magnetic ordering phenomena, for which we propose a consistent picture based on the change from antiferromagnetic to ferromagnetic coupling between the chains. Electronic structure calculations confirm the antiferromagnetic ordering as the ground state for Cs(3)Mn(2)O(4) and ferrimagnetic ordering as its nearly degenerate state.     

Synthesis, growth, optical, mechanical, dielectric and thermal properties of 4-chloro-4'-chlorobenzylidene aniline single crystal

The organic material 4-chloro-4′-chlorobenzylidene aniline (CCBA) was synthesized and confirmed by NMR and FTIR spectral analyses. CCBA crystal was grown from chloroform by slow evaporation at room temperature and the single crystal cell parameters were determined by single crystal X-ray diffraction method. The perfection of the grown crystal was analyzed by high resolution X-ray diffraction rocking curve analysis. Fluorescence spectrum indicated violet emission at 428 nm. The range of optical absorbance was ascertained by recording UV–vis–NIR spectrum. Load dependant microhardness measurements on this crystal revealed the mechanical behavior of the material. Stiffness constant, Meyer index and yield strength of CCBA crystal were calculated. Dielectric studies were carried out to estimate the dielectric parameters of the grown crystal in the frequency range from 100 Hz to 100 kHz. The thermal behavior of CCBA was investigated using differential scanning calorimetry (DSC) and no phase transition was identified in the temperature region 30–100 °C. Further, the CCBA crystal was subjected to open aperture Z-scan studies in order to investigate the third order nonlinear optical (NLO) properties of CCBA crystal.     

Synthesis,characterization, crystal structures,and magnetic properties of two new dissymmetrical Schiff-base metal complexes

Two dissymmetrical Schiff-base metal complexes, [CuL1]₂ (1) (L1 = N-3-carboxylsalicylidene-N-5-bromosalicylaldehyde-1,3-diaminopentane) and [NiL2] · H₂O (2) (L2 = N-5-bromosalicylaldehyde-1,3-diaminopentane), have been synthesized and characterized by IR, elemental analyses, magnetic studies, and the crystal structures. The crystal structure of 1 contains one binuclear molecule in which each central Cu has N₂O₃ coordination. The magnetism of 1 has been determined in the temperature range of 5–300 K. Results indicate that interaction between the two Cu ions is weak antiferromagnetic. The crystal structure of 2 shows mononuclear structure with similar structural features. Through intermolecular hydrogen-bonding interactions, 2 gives an infinite chain structure.     

Synthesis, crystal structures and DNA-binding properties of two new mononuclear copper(II) complexes

Two mononuclear copper(II) complexes, [Cu(bpy)₂(CH₃OH)](pic)₂ (1) and [Cu(Me₂bpy)₂(H₂O)](pic)₂ (2) (bpy = 2,2′-bipyridine; Me₂bpy = 4,4′-dimethyl-2,2′-bipyridine; Hpic = 2,4,6-trinitrophenol), were synthesized and characterized by elemental analyses, conductivity measurements, IR, UV–Visible spectroscopy and single crystal X-ray analyses. Both complexes 1 and 2 are mononuclear compounds. The copper atom in complex 1 is in a distorted square pyramidal geometry with a CuN₄O chromophore as revealed from the τ value (0.25), while the Cu(II) ion in complex 2 displays a distorted trigonal bipyramidal stereochemistry with τ = 0.72. Hydrogen bonding interactions and π–π stacking interactions link the mononuclear copper complex 1 or 2 into a 1D infinite chain. The interactions of the two mononuclear complexes with herring sperm DNA (HS-DNA) have been studied by UV–visible absorption titration, fluorescence titration and ethidium bromide (EB) displacement experiments. The results suggest that both complexes might bind to DNA by intercalation.     

Solvothermal syntheses,crystal structures,and optical and thermal properties of transition metal selenidostannates

Four organic–inorganic hybrid selenidostannates, namely [H₂en][H₂dien][Fe(dien)₂]₂(Sn₂Se₆)₂ (1), [Fe(dien)₂]₂Sn₂Se₆ (2), [Fe(dien)₂]FeSnSe₄ (3), and [Mn(dien)₂]MnSnSe₄ (4) (en = ethylenediamine; dien = diethylenetriamine), were prepared in different solvents under solvothermal conditions. Complexes 1 and 2 consist of discrete [Sn₂Se₆]^4? and [Fe(dien)₂]²⁺ ions, as well as organic cations [H₂en]²⁺ and [H₂dien]²⁺ in 1. The dimeric [Sn₂Se₆]^4? anion is formed by two SnSe₄ tetrahedra via edge-sharing. Complexes 3 and 4 are composed of one-dimensional polyanions [TMSnSe ₄ ^2? ] _n plus [TM(dien)₂]²⁺ counter cations (TM = Fe, Mn). In the [TMSnSe ₄ ^2? ] _n anionic chain, the TM and Sn atoms are located at the same metal site with a ratio of 0.5/0.5. The TM_1/2Sn_1/2Se₄ tetrahedra are interlinked via edge-sharing, forming the heterometallic [TMSnSe ₄ ^2? ] _n polymeric anion. The [TM(dien)₂]²⁺ cations in 1–2 and 3–4 have u-fac and mer configurations, respectively. In all four crystal structures, the anions and cations are connected into extended structures via weak N–H···Se hydrogen bonds. The band gaps of complexes 1–4 calculated from the solid-state UV–vis diffuse reflectance spectra were at 2.58, 2.60, 2.21, and 2.25 eV, respectively. Thermogravimetric analyses show that complex 1 decomposes in three steps, while complexes 2–4 each decompose in one step.     

Yttrium thiocyanate-based supramolecular architectures: Synthesis, crystal structures, and thermal properties

The reaction of [Y(H₂O)₅(NCS)₃]·H₂O (1) with crown ether (18-crown-6) and KNCS in methanol afforded the complexes [Y(H₂O)₄(NCS)₃]·1.5(18-crown-6) (2) and [K(18-crown-6)(H₂O)_1.25]_2n{[K(18-crown-6)]₂[Y(NCS)₆]}_n·n(NCS) (3). In mononuclear complex 1, yttrium has a coordination number 8 and forms the coordination unit YO₅N₃. Complexes 1 are linked by hydrogen bonds to form a framework. The crystal structure of 2 contains the centrosymmetric ensembles [Y(H₂O)₄(NCS)₃]₂(18-crown-6)₃ formed via hydrogen bonds. In the crystal structure of 3, the [Y(NCS)₆]³⁻ anions and the [K(18-crown-6)]⁺ cations form one-dimensional polymeric chains (-Y-NCS-K-)_n. The thermal behavior of compounds 1 and 2 was investigated. It was shown that the supramolecular assembly has an effect on the temperature range for the removal of coordinated water molecules from the thiocyanate complex. The oxidative decomposition of the acido ligands in 1 and 2 occurs in a similar way to give Y₂O₂SO₄ as the final product (700 °С).     

Synthesis, crystal structure, and optical properties of LiGd5P2O13, a layered lithium gadolinium phosphate containing one-dimensional Li chains

A lithium gadolinium phosphate crystal, LiGd5P2O13, has been synthesized by a high temperature solution reaction and solved by single-crystal X-ray diffraction data. The structure is monoclinic, space group C2/m, with unit cell parameters a = 18.645(3), b = 5.6257(5), c = 12.014(2) A, beta = 117.55(6)degrees, V = 1117.3(3) A3, and Z = 4. LiGd5P2O13 presents a new structural type and is built up from [Gd5P2O13]- layers and one-dimensional Li chains with an unusual Li-Li distance. The optical properties were investigated in terms of the absorption and emission spectra. Additionally, the calculations of band structure, density of states, dielectric constants, and refractive indexes were performed with the density functional threory method. The obtained results tend to support the experimental data.     

Synthesis,crystal structures and properties of two copper(II) 2-aminomethylbenzimidazole complexes

Two new Cu^II complexes, [Cu(Hambi)₂(ClO₄)₂] and [Cu(Hambi)₂(dca)₂] (Hambi = 2-aminomethylbenzimidazole) have been prepared and characterized by X-ray diffraction, electronic paramagnetic resonance (e.p.r.) and i.r. analyses. Both complexes exhibit an elongated octahedral coordination environment with two Hambi ligands situated at the equatorial positions in a trans fashion [Cu—N bond distances range from 1.940(9) to 2.031(9) Å]. In the second complex, a new coordination mode, in which dicyanamide coordinates to copper(II) as a monodentate ligand with the amide nitrogen atom, was observed.     

Syntheses, crystal structures and characterizations of two new quaternary thioborates: PbMBS4 (M = Sb, Bi)

Two new quaternary thioborates, PbSbBS(4) and PbBiBS(4), have been synthesized from solid-state reaction methods at temperatures from 1073 to 1123 K in evacuated sealed quartz tubes. The crystal structures have been determined by means of single crystal X-ray diffraction and they both crystallize in the P2(1)/m space group of the monoclinic system with a = 5.9532(18) ?, b = 6.2031(13) ?, c = 9.250(3) ?, β = 108.200(16)°, Z = 2 for PbSbBS(4) and a = 5.971(10) ?, b = 6.273(9) ?, c = 9.132(15) ?, β = 107.75(2)°, Z = 2 for PbBiBS(4), respectively. The two compounds are isostructural and both constructed with the infinite one-dimensional [MBS(4)](2-) (M = Sb or Bi) chains as building blocks, which are composed of [BS(3)](3-) trigonal plane units with [MS(3)](3-) (M = Sb or Bi) trigonal pyramids connected alternatively through corner-sharing along the crystallographic b axis. Two adjacent [MBS(4)](2-) chains are further bridged by the intermediate Pb(2+) cations, forming a novel S-shaped Pb-[MBS(4)] dimeric chain structure. In addition, first-principles electronic structure calculations based on the density functional theory (DFT) were performed on compound PbSbBS(4), indicating that the compound belongs to direct semiconductor with a band gap of 1.803 eV, which is in good agreement with the experimental value estimated from the UV-Vis diffuse reflectance spectroscopy.     

Synthesis, growth, thermal, optical and mechanical properties of 2-Aminopyridinium 4-methylbenzoate Dihydrate

Organic NLO material of 2-Aminopyridinium 4-methylbenzoate Dihydrate (2A4M) was synthesized using 2-Aminopyridinium and 4-methylbenzoic acid as starting materials. Single crystals of 2A4M were grown by the slow evaporation solution growth technique at room temperature using water as a solvent. The grown crystal was characterized by single crystal XRD to confirm the crystal system and lattice parameters. From the optical studies the optical band gap and the refractive index of the material are found to be 2.9 eV and 1.40 at 1200 nm. Functional groups of the crystallised material were confirmed by FTIR vibrational spectrum. Thermal behaviour of the title compound was studied using thermogravimetric (TG) and differential thermal analyses (DTA). The initial weight loss is found up to 125°C, which corresponds to 13.2% i.e. presence of 2 mole of water in the lattice. The grown crystal was subjected to Vickers hardness test and the brittleness index, fracture toughness, yield strength were estimated. The etching studies reveal the growth pattern and dislocations present in the grown crystal. The second harmonic generation (SHG) behaviour of 2A4M was tested by Kurtz-Perry powder technique. The relative SHG efficiency of 2A4M is found to be 3.03 times that of the reference material KDP.     

Synthesis, crystal structures, and luminescent properties of two types of lanthanide phosphonates

Hydrothermal reactions of different lanthanide(III) salts with an amino-diphosphonate ligand (H₄L=C₆H₅CH₂N(CH₂PO₃H₂)₂) led to two series of lanthanide phosphonates, namely, Ln(H₂L)(H₃L) (Ln=La, 1; Pr, 2; Nd, 3; Sm, 4; Eu, 5; Gd, 6; Tb, 7). Compounds 1-5 feature a one-dimensional (1D) chain structure in which dimers of two edge-sharing LnO₈ polyhedra are interconnected by bridging phosphonate groups, such 1D arrays are further interlinked via strong hydrogen bonds between non-coordinated phosphonate oxygen atoms into a two-dimensional (2D) layer with the phenyl groups of the ligands orientated toward the interlayer space. Compounds 6 and 7 also show a different 1D array in which the LnO₆ octahedra are bridged by phosphonate groups via corner-sharing, such chains are also further interlinked by hydrogen bonds into a 2D supramolecular layer. Compounds 5 and 7 emit red and green light with a lifetime of 2.1 and 3.7 ms, respectively.