Synthesis and characterization of zinc bis(O‐isopropylxanthate) as a single‐source chemical vapor deposition precursor for ZnS

The utilization of single‐source molecular precursors in chemical vapor deposition (CVD) experiments requires a deep knowledge of their chemico‐physical properties, with particular regard to thermal stability and fragmentation pattern. This study describes the synthesis and characterization of zinc bis(O‐isopropylxanthate), Zn(O‐ⁱPrXan)₂, [O‐ⁱPrXan = (CH₃)₂CHOCS₂], a single‐source precursor for the CVD of zinc(II) sulfide thin films and nanorods. Several analytical methods yielding complementary information (extended X‐ray absorption fine structure, Raman, FT‐IR, UV–Vis optical absorption, ¹H and ¹³C NMR, thermogravimetric analysis, differential scanning calorimetry as well as mass spectrometry techniques, i.e. electrospray and electron ionization, mass‐analyzed ion kinetic energy) are adopted for a comprehensive investigation of purity, structure, thermal behavior and decomposition pathways of the molecule. The most significant results are discussed critically and the properties useful for CVD applications are highlighted. Copyright © 2005 John Wiley & Sons, Ltd.     

Scaled‐up,selective and green synthesis of sulfoxides under mild conditions using (CeIII‐MoVI)Ox/aniline hybrid rods as an efficient catalyst

A novel hybrid material, (Ce^III‐Mo^VI)O_x/aniline, with rod‐like morphology is synthesized through a wet chemical method using Mo₃O₁₀(C₆H₅NH₃)₂.2H₂O nanowires as precursor. The synthesized materials are characterized by XRD, XPS, SEM, TEM, FTIR, Raman, UV–Vis, TGA, and elemental analysis. Also, their catalytic activities as a hybrid catalyst are tested in the selective oxidation of sulfides using hydrogen peroxide as a green oxidant. The proposed novel hybrid catalyst shows an excellent performance under green conditions at mild temperature. Furthermore, the scalability of the oxidation reaction is shown by making multi‐gram quantities at optimized conditions.     

Cadmium O‐alkylxanthates as CVD precursors of CdS: a chemical characterization

Cadmium bis(O‐alkylxanthates) are potential single‐source molecular precursors for the chemical vapor deposition (CVD) of Cd(II) sulfide thin films. In this work, a multi‐technique characterization of Cd(O‐RXan)₂ compounds [where O‐RXan is CH₃CH₂OCS₂ (O‐EtXan) or (CH₃)₂CHOCS₂ (O‐ⁱPrXan)] is performed by means of several analytical methods (extended x‐ray absorption fine structure, Raman, Fourier transform infrared and optical absorption, spectroscopics ¹H and ¹³C NMR, thermal analysis and mass spectrometry) for a thorough investigation of their structure and chemical–physical properties. The most important results concerning the chemical behavior under different experimental conditions, with particular attention to relevant properties for CVD applications, are presented and discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

Two zinc(II) coordination complexes based on an asymmetric multidentate ligand: syntheses,structures, selective fluorescence sensing of iron(III) ions and thermal analyses

The rational selection of ligands is vitally important in the construction of coordination complexes. Two novel Zn^II complexes, namely bis(acetato‐κO)bis[1‐(1H‐benzotriazol‐1‐ylmethyl)‐2‐propyl‐1H‐imidazole‐κN³]zinc(II) monohydrate, [Zn(C₁₃H₁₅N₅)₂(C₂H₃O₂)₂]·H₂O, ( 1 ), and bis(azido‐κN¹)bis[1‐(1H‐benzotriazol‐1‐ylmethyl)‐2‐propyl‐1H‐imidazole‐κN³]zinc(II), [Zn(C₁₃H₁₅N₅)₂(N₃)₂], ( 2 ), constructed from the asymmetric multidentate imidazole ligand, have been synthesized under mild conditions and characterized by elemental analyses, IR spectroscopy and single‐crystal X‐ray diffraction analysis. Both complexes exhibit a three‐dimensional supramolecular network directed by different intermolecular interactions between discrete mononuclear units. The complexes were also investigated by fluorescence and thermal analyses. The experimental results show that ( 1 ) is a promising fluorescence sensor for detecting Fe³⁺ ions and ( 2 ) is effective as an accelerator of the thermal decomposition of ammonium perchlorate.     

Preparation of Barium Titanate Nanopowder through Thermal Decomposition of Peroxide Precursor and Its Formation Mechanism

H₂TiO₃ was dissolved in the mixture of hydrogen formed peroxide and ammonia under the pH range of 8–10 with a transparent yellow solution formed. When an equivalent mole of Ba²⁺ solution was added into the yellow solution, the precipitate produced was the peroxide precursor of barium titanate. The cubic nanopowder of barium titanate was obtained when the precipitate was washed, stoved, and then calcined at 600°C for 1 h. The peroxide precursor of barium titanate and barium titanate nanopowder prepared were characterized to be BaTi(H₂O₂)₂O₃ by TGA‐DTA, XRD, TEM, SEM, and XREDS. The peroxide precursor of barium titanate was determined to be BaTi(H₂O₂)₂O₃. The particle size of the barium titanate nanopowder, the calcined product of BaTi(H₂O₂)₂O₃, was in the range of 20–40 nm. A formation mechanism of the barium titanate nanopowder through thermal decomposition of its peroxide precursor was proposed and then validated.     

Synthesis,structure and magnetism of a new ionic pentanuclear iron cluster

A new ionic pentanuclear Fe^III cluster, namely, triethylazanium tetrakis(μ₂‐5‐amino‐1,2,3,4‐tetrazolido)tetrakis(μ₃‐4‐chloro‐2‐{[(1H‐tetrazol‐1‐id‐5‐yl)imino]methyl}phenolato)di‐μ₃‐oxido‐pentairon(III) acetonitrile monosolvate monohydrate, (C₆H₁₆N)[Fe₅(C₈H₄ClN₅O)₄(CH₂N₅)₄O₂]·CH₃CN·H₂O, was synthesized using microvial synthesis methods and characterized by elemental analysis, FT–IR spectroscopy, single‐crystal X‐ray diffraction and thermogravimetric analysis. Magnetic studies reveal that the complex displays dominant antiferromagnetic intracluster interactions between the Fe^III ions through the μ₃‐oxide bridges.     

Synthesis and Structural Characterization of β‐Ketoiminate‐Stabilized Gallium Hydrides for Chemical Vapor Deposition Applications

Bis‐β‐ketoimine ligands of the form [(CH₂)_n{N(H)C(Me)?CHC(Me)?O}₂] (LⁿH₂, n=2, 3 and 4) were employed in the formation of a range of gallium complexes [Ga(Lⁿ)X] (X=Cl, Me, H), which were characterised by NMR spectroscopy, mass spectrometry and single‐crystal X‐ray diffraction analysis. The β‐ketoimine ligands have also been used for the stabilisation of rare gallium hydride species [Ga(Lⁿ)H] (n=2 ( 7 ); n=3 ( 8 )), which have been structurally characterised for the first time, confirming the formation of five‐coordinate, monomeric species. The stability of these hydrides has been probed through thermal analysis, revealing stability at temperatures in excess of 200 °C. The efficacy of all the gallium β‐ketoiminate complexes as molecular precursors for the deposition of gallium oxide thin films by chemical vapour deposition (CVD) has been investigated through thermogravimetric analysis and deposition studies, with the best results being found for a bimetallic gallium methyl complex [L³{GaMe₂}₂] ( 5 ) and the hydride [Ga(L³)H] ( 8 ). The resulting films ( F5 and F8 , respectively) were amorphous as‐deposited and thus were characterised primarily by XPS, EDXA and SEM techniques, which showed the formation of stoichiometric ( F5 ) and oxygen‐deficient ( F8 ) Ga₂O₃ thin films.     

Nanostructured ZrO2 and Zr‐C‐N Coatings from Chemical Vapor Deposition of Metal‐Organic Precursors

Nanocrystalline zirconium carbonitride (Zr‐C‐N) and zirconium oxide (ZrO₂) films were deposited by chemical vapor deposition (CVD) of zirconium‐tetrakis‐diethylamide (Zr(NEt₂)₄) and ‐tert‐butyloxide (Zr(OBu^t)₄), respectively. The films were deposited on iron substrates and characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The Zr‐C‐N films show blue, golden brown or bronze colours, with colour stability depending upon the precursor composition (pure metal amide or mixed with Et₂NH). The deposition temperature showed no pronounced effect on the granular morphology of the Zr‐C‐N films. The XRD data of the films correspond to the formation of carbonitride phase whereas the XPS analyses revealed a strong surface oxidation and incorporation of oxygen in the film. The films deposited using a mixture of Zr(NEt₂)₄ and Et₂NH showed higher N content, better adhesion and scratch resistance when compared to films obtained from the CVD of pure Zr(NEt₂)₄. Subject to the precursor composition and deposition temperature (550‐750 °C), the microhardness values of Zr‐C‐N films were found to be in the range 2.11‐5.65 GPa. For ZrO₂ films, morphology and phase composition strongly depend on the deposition temperature. The CVD deposits obtained at 350 °C show tetragonal ZrO₂ to be the only crystalline phase. Upon increasing the deposition temperature to 450 °C, a mixture of tetragonal and monoclinic modifications was formed with morphology made up of interwoven elongated grains. At higher temperatures (550 and 650 °C), pure monoclinic phase was obtained with facetted grains and developed texture.     

Di‐μ2‐sulfito‐κ8O,O′:O′,O′′‐bis[(2,4,6‐tri‐2‐pyrid­yl‐1,3,5‐triazine‐κ3N2,N1,N6)cadmium(II)] octa­hydrate

The title compound, [Cd₂(SO₃)₂(C₁₈H₁₂N₆)₂]·8H₂O, is a dimer built up around a symmetry center, where the sulfite anion displays a so far unreported coordination mode in metal‐organic complexes; the anion binds as a μ₂‐sulfite‐κ⁴O,O′:O′,O′′ ligand to two symmetry‐related seven‐coordinate Cd^II cations, binding through its three O atoms by way of two chelate bites with an O atom in common, which acts as a bridge. The cation coordination is completed by a 2,4,6‐tri‐2‐pyridyl‐1,3,5‐triazine ligand acting in its usual tridentate mode.     

Copper(II) complexes of acylhydrazones: synthesis,characterization and DNA interaction

Two new acylhydrazone copper(II) complexes of 4‐hydroxy‐N′‐[(1E)‐1‐(4‐methylphenyl)ethylidene]benzohydrazide (HL¹) and 4 ethyl [4‐({(2E)‐2‐[1‐(4‐methylphenyl)ethylidene]hydrazinyl}carbonyl)phenoxy]acetate (HL²) have been synthesized and characterized. The structures of both acylhydrazone and copper(II) complexes were identified by elemental analysis, infrared spectra, UV–visible electronic absorption spectra, magnetic susceptibility measurements, TGA and powder X‐ray diffraction. DNA binding and DNA cleavage activities of the synthesized copper complexes were examined by using UV‐visible titration and agarose gel electrophoresis, respectively. The effect of complex concentration on the DNA cleavage reactions in the absence and presence of H₂O₂ was also investigated. The results indicate that all the complexes bind slightly to calf thymus DNA and cleavage pBR322 DNA. The mechanistic studies demonstrate that a hydrogen peroxide‐derived species and singlet oxygen (¹O₂) are the active oxidative species for DNA cleavage. Copyright © 2013 John Wiley & Sons, Ltd.     

Volatile dimethylgold(III) complex with di-iso-butyldithiophosphinate ligand: synthesis,structure, and thermal behavior in condensed and gas phase

Synthesis and molecular structure of air stable, low-melting dimethylgold(III) complex with dithiophosphinate (CH₃)₂AuS₂PⁱBu² (ⁱBu=CH₂CH(CH₃)₂), its thermal properties, and the features as precursor for the metal–organic chemical vapor deposition of gold films are reported. Thermal behavior of the compound in the condensed and gas phase was studied by thermogravimetric analysis and mass spectrometry. Pathways of heterogeneous thermolysis of the compound to elemental gold are discussed. It was found that α-P–H elimination followed by coupling of two alkenyl groups from the coordinated ligand is one of the main thermolysis pathways in condensed and gas phase.     

Synthesis of Co3O4 nanorod bunches from a single precursor Co(CO3)0.35Cl0.20(OH)1.10

Co₃O₄ nanorods were successfully synthesized from a single precursor via a thermal decomposition and oxidization route. The precursor used was Co(CO₃)_0.35Cl_0.20(OH)_1.10, which was prepared by a hydrothermal reaction using CoCl₂⋅6H₂O with CO(NH₂)₂ at 95–120 °C. Both the precursor and the as-prepared Co₃O₄ were characterized with XRD, TEM, SEM, TGA and XPS. The precursor, as well as Co₃O₄, was found to be composed of nanorods that were radially bunched. The Co₃O₄ nanorods obtained through a thermal treatment at 300 °C for 5 h were found to have a porous structure.     

Magnetism and crystal structure of an N3O3‐coordinated iron(II) complex

The reaction of [FeL(MeOH)₂] {where L is the tetradentate N₂O₂‐coordinating Schiff base‐like ligand (E,E)‐diethyl 2,2′‐[1,2‐phenylenebis(nitrilomethylidyne)]bis(3‐oxobutanoate)(2−) and MeOH is methanol} with 3‐aminopyridine (3‐apy) in methanol results in the formation of the octahedral complex (3‐aminopyridine‐κN¹){(E,E)‐diethyl 2,2′‐[1,2‐phenylenebis(nitrilomethylidyne)]bis(3‐oxobutanoato)(2−)‐κ⁴O³,N,N′,O^3′}(methanol‐κO)iron(II), [Fe(C₂₀H₂₂N₂O₆)(C₅H₆N₂)(CH₄O)] or [FeL(3‐apy)(MeOH)], in which the Fe^II ion is centered in an N₃O₃ coordination environment with two different axial ligands. This is the first example of an octahedral complex of this multidentate ligand type with two different axial ligands, and the title compound can be considered as a precursor for a new class of complexes with potential spin‐crossover behavior. An infinite two‐dimensional hydrogen‐bond network is formed, involving the amine NH group, the methanol OH group and the carbonyl O atoms of the equatorial ligand. T‐dependent susceptibility measurements revealed that the complex remains in the high‐spin state over the entire temperature range investigated.     

Synthesis,Structure, Photoluminescence and Thermal Properties of Sodium Ethene‐Bis‐Nitrobenzenesulfonate

Abstract. Sodium ethene‐bis‐nitrobenzenesulfonate, [Na₂(ENS) · 6H₂O]_n( 1 ) was synthesized through coupling reaction of o‐nitrotoluenesulfonic acid in NaOH solution and characterized by single crystal X‐ray diffraction, elemental analysis, IR and ¹H NMR spectroscopy, XRPD, DSC and TGA (where ENS^2– = ethene‐bis‐nitrobenzenesulfonate). The asymmetrical unit of ( 1 ) consists of two octahedral Na^I ions, and the neighboring metal centers are bridged by μ₂ water molecules resulting in the formation of an inorganic tetranuclear unit. The tetranuclear units were connected through the ENS^2– ligands into a 2D topology net. The weak π–π stacking and H‐bonding interactions further stabilized the structure. The crystals of (C₇H₆NO₅S)^– · (H₅O₂)⁺ ( 2 ) were obtained by post‐processing the unreacted raw material to recycle. Furthermore, the rigidity and the conjugation effect of the aromatic system in compound 1 were increased through the coordination interactions of metal atoms to ligands, resulting in the emission coming from ligand enhanced with red‐shifting about 9 nm of the maximal wavelength. The conjugation effects and the steric arrangement of the substituent groups play the main role to the luminescence intensity and red‐shift effect.     

FeIII in a low‐spin state in caesium bis[3‐ethoxysalicylaldehyde 4‐methylthiosemicarbazonato(2–)‐κ3O2,N1,S]ferrate(III) methanol monosolvate

The synthesis and crystal structure (at 100 K) of the title compound, Cs[Fe(C₁₁H₁₃N₃O₂S₂)₂]·CH₃OH, is reported. The asymmetric unit consists of an octahedral [Fe^III(L)₂]⁻ fragment, where L²⁻ is 3‐ethoxysalicylaldehyde 4‐methylthiosemicarbazonate(2−) {systematic name: [2‐(3‐ethoxy‐2‐oxidobenzylidene)hydrazin‐1‐ylidene](methylamino)methanethiolate}, a caesium cation and a methanol solvent molecule. Each L²⁻ ligand binds through the thiolate S, the imine N and the phenolate O atoms as donors, resulting in an Fe^IIIS₂N₂O₂ chromophore. The O,N,S‐coordinating ligands are orientated in two perpendicular planes, with the O and S atoms in cis positions and the N atoms in trans positions. The Fe^III cation is in the low‐spin state at 100 K.     

The new one‐dimensional coordination polymer catena‐poly[[diaquasodium(I)]‐μ‐oxalato‐[diaquairon(III)]‐μ‐oxalato]

The oxalate dianion is one of the most studied ligands and is capable of bridging two or more metal centres and creating inorganic polymers based on the assembly of metal polyhedra with a wide variety of one‐, two‐ or three‐dimensional extended structures. Yellow single crystals of a new mixed‐metal oxalate, namely catena‐poly[[diaquasodium(I)]‐μ‐oxalato‐κ⁴O¹,O²:O^1′,O^2′‐[diaquairon(III)]‐μ‐oxalato‐κ⁴O¹,O²:O^1′,O^2′], [NaFe(C₂O₄)₂(H₂O)₄]_n, have been synthesized and the crystal structure elucidated by X‐ray diffraction analysis. The compound crystallizes in the noncentrosymmetric space group I4₁ (Z = 4). The asymmetric unit contains one Na^I and one Fe^III atom lying on a fourfold symmetry axis, one μ₂‐bridging oxalate ligand and two aqua ligands. Each metal atom is surrounded by two chelating oxalate ligands and two equivalent water molecules. The structure consists of infinite one‐dimensional chains of alternating FeO₄(H₂OW1)₂ and NaO₄(H₂OW2)₂ octahedra, bridged by oxalate ligands, parallel to the [100] and [010] directions, respectively. Because of the cis configuration and the μ₂‐coordination mode of the oxalate ligands, the chains run in a zigzag manner. This arrangement facilitates the formation of hydrogen bonds between neighbouring chains involving the H₂O and oxalate ligands, leading to a two‐dimensional framework. The structure of this new one‐dimensional coordination polymer is shown to be unique among the A^IM^III(C₂O₄)₂(H₂O)_n series. In addition, the absorption bands in the IR and UV–Visible regions and their assignments are in good agreement with the local symmetry of the oxalate ligand and the irregular environment of iron(III). The final product of the thermal decomposition of this precursor is the well‐known ternary oxide NaFeO₂.     

Synthesis,Characterization, Thermal Property of Si(c‐C5H9NH)4 and Its Potential as CVD Precursor for SiC Film

Silicon(IV) amide Si(c‐C₅H₉NH)₄ ( 1 ), was synthesized and characterized by ¹H, ¹³C, and ²⁹Si NMR spectroscopy, EI‐MS, elemental analysis, and X‐ray diffraction. Its thermal stability and volatility were also investigated. The as‐grown film, which was characterized by SEM, AFM, XRD and XPS, was deposited using 1 as single precursor through a low‐pressure chemical vapor deposition (LPCVD) process at a temperature as low as 600 °C. The results demonstrated that silicon(IV) amides can be promising single‐precursor for deposition of low‐temperature SiC films.     

An Oxalate‐Bridged Copper(II) Dimer and a Mononuclear ­Cobalt(III) Azide Complex Containing N‐Nitrile‐Functionalized 1, 4, 7‐Triazacyclononane Terminals: Synthesis,Crystal Structure,and Magnetic Characterization

The stable dinuclear [Cu(μ‐C₂O₄)Cu]²⁺ entity is facially coordinated at each end by a N‐nitrile functionalized triazamacrocycle, 1, 4, 7‐tris(cyanomethyl)‐1, 4, 7‐triazacyclononane ( L ), to generate a centrosymmetric compound [Cu₂ L ₂(μ‐C₂O₄)](ClO₄)₂ · 4DMF ( 1 ) containing a bis‐bidentate oxalate bridge. The variable‐temperature magnetic measurement for the crystallographically characterized compound exhibits quite strong antiferromagnetic coupling interaction between two oxalate‐linked Cu^II atoms separated by 5.149 Å with a singlet‐triplet energy gap of –345.5 cm^–1. On the other hand, a mononuclear Co^III compound [Co L (N₃)₃] · 2.5H₂O ( 2 ) with monodentate azide terminal groups was synthesized. Structural elucidation by X‐ray diffraction shows that the compound has crystallographically imposed C₃ symmetry. Enantiomerically pure crystals were obtained upon crystallization indicated by a Flack parameter of 0.04(5).     

Designing a heterotrinuclear CuII—NiII—CuII complex from a mononuclear CuII Schiff base precursor with dicyanamide as a coligand: synthesis,crystal structure,thermal and photoluminescence properties

Schiff bases are considered `versatile ligands' in coordination chemistry. The design of polynuclear complexes has become of interest due to their facile preparations and varied synthetic, structural and magnetic properties. The reaction of the `ligand complex' [CuL] {H₂L is 2,2′‐[propane‐1,3‐diylbis(nitrilomethanylylidene)]diphenol} with Ni(OAc)₂·4H₂O (OAc is acetate) in the presence of dicyanamide (dca) leads to the formation of bis(dicyanamido‐1κN¹)bis(dimethyl sulfoxide)‐2κO,3κO‐bis{μ‐2,2′‐[propane‐1,3‐diylbis(nitrilomethanylylidene)]diphenolato}‐1:2κ⁶O,O′:O,N,N′,O′;1:3κ⁶O,O′:O,N,N′,O′‐dicopper(II)nickel(II), [Cu₂Ni(C₁₇H₁₆N₂O₂)₂(C₂N₃)₂(C₂H₆OS)₂]. The complex shows strong absorption bands in the frequency region 2155–2269 cm⁻¹, which clearly proves the presence of terminal bonding dca groups. A single‐crystal X‐ray study revealed that two [CuL] units coordinate to an Ni^II atom through the phenolate O atoms, with double phenolate bridges between Cu^II and Ni^II atoms. Two terminal dca groups complete the distorted octahedral geometry around the central Ni^II atom. According to differential thermal analysis–thermogravimetric analysis (DTA–TGA), the title complex is stable up to 423 K and thermal decomposition starts with the release of two coordinated dimethyl sulfoxide molecules. Free H₂L exhibits photoluminescence properties originating from intraligand (π–π*) transitions and fluorescence quenching is observed on complexation of H₂L with Cu^II.     

Synthesis,Characterization, Electronic and Gas‐Sensing Properties towards H2 and CO of Transparent,Large‐Area,Low‐Layer Graphene

Low‐layered, transparent graphene is accessible by a chemical vapor deposition (CVD) technique on a Ni‐catalyst layer, which is deposited on a <100> silicon substrate. The number of graphene layers on the substrate is controlled by the grain boundaries in the Ni‐catalyst layer and can be studied by micro Raman analysis. Electrical studies showed a sheet resistance (R_sheet) of approximately 1435 Ω per □, a contact resistance (R_c) of about 127 Ω, and a specific contact resistance (R_sc) of approximately 2.8×10^?4 Ω cm² for the CVD graphene samples. Transistor output characteristics for the graphene sample demonstrated linear current/voltage behavior. A current versus voltage (I_ds–V_ds) plot clearly indicates a p‐conducting characteristic of the synthesized graphene. Gas‐sensor measurements revealed a high sensor activity of the low‐layer graphene material towards H₂ and CO. At 300 °C, a sensor response of approximately 29 towards low H₂ concentrations (1 vol %) was observed, which is by a factor of four higher than recently reported.