Synthesis, characterization, and thermal properties of homoleptic rare-earth guanidinates: promising precursors for MOCVD and ALD of rare-earth oxide thin films

Eight novel homoleptic tris-guanidinato complexes M[(N(i)Pr)(2)CNR(2)](3) [M = Y (a), Gd (b), Dy (c) and R = Me (1), Et (2), (i)Pr (3)] have been synthesized and characterized by NMR, CHN-analysis, mass spectrometry and infrared spectroscopy. Single crystal structure analysis revealed that all the compounds are monomers with the rare-earth metal center coordinated to six nitrogen atoms of the three chelating guanidinato ligands in a distorted trigonal prism geometry. With the use of TGA/DTA and isothermal TGA analysis, the thermal characteristics of all the complexes were studied in detail to evaluate their suitability as precursors for thin film deposition by MOCVD and ALD. The (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) showed excellent thermal characteristics in terms of thermal stability and volatility. Additionally, the thermal stability of the (i)Pr-Me(2)N-guanidinates of Y and Dy (1a, c) in solution was investigated by carrying out NMR decomposition experiments and both the compounds were found to be remarkably stable. All these studies indicate that (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) have the prerequisites for MOCVD and ALD applications which were confirmed by the successful deposition of Gd(2)O(3) and Dy(2)O(3) thin films on Si(100) substrates. The MOCVD grown films of Gd(2)O(3) and Dy(2)O(3) were highly oriented in the cubic phase, while the ALD grown films were amorphous.     

Synthesis, characterization and sensing application of novel semiconductor oxides

Mesoporous SnO(2) with high surface areas were synthesized using a cationic surfactant (N-cetyl-N,N,N-trimethylammonium bromide) as a synthetic template. Acidity of the starting synthesis slurry was used as one of the controlling parameters for the synthesis. After the SnO(2) was synthesized at pH 7.15, it was calcined at 723 K for 10 h in air. It had a BET surface area of 156.8 m(2) g(-1) with a pore diameter of 38.4 A. Infrared spectroscopy (FTIR) and thermal analysis techniques (thermogravimetry and differential thermal analysis) showed that the surfactant was incorporated in the mesopores of SnO(2) and calcination in air at 673-723 K was needed to remove the surfactant completely from the mesopores. The effects of SnO(2) surface area on its gas sensing properties were also investigated. It was observed that SnO(2) with higher surface areas had much higher sensitivities to hydrogen at 573 K.     

Cyclodextrin inclusion complexes as novel MOCVD precursors for potential cobalt oxide deposition

The potential use of the inclusion complexes of β‐cyclodextrins with metal halides as novel precursors in MOCVD applications was examined in terms of microstructure, thermal stability and chemical modifications during heating. The investigation was especially focused on the inclusion complex of β‐cyclodextrin with cobalt iodide for cobalt oxide thin film deposition. The general composition assigned to the dextrin's inclusion complex was: (β‐CD)₂^?CoI₇^?11H₂O. It was found that the inclusion complex of β‐cyclodextrin with CoI₂ may prove a promising alternative to traditional metalorganic or organometallic Co‐precursors for precise CVD applications. The sublimation temperature must be preferably in the range 70–125 °C, and the decomposition temperature (substrate temperature) in the range of 350–400 °C. Three distinct regions can be recognized by heating: transformation of tightly bound water molecules into easily movable ones, sublimation of iodine ions and Co atoms oscillation and thermal decomposition of the glycositic ring into volatile by‐products. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis, characterization and thermal decomposition of thiourea complexes of antimony and bismuth triiodide

The thiourea complexes of antimony and bismuth triiodide were synthesized by a direct reaction of antimony and bismuth triiodide with thiourea powder at room temperature. The formula of the complex is MI₃[SC(NH₂)₂]₃(M=Sb, Bi). The crystal structure of the complexes belongs to monoclinic system and the lattice parameters are a=1.4772 nm, b=1.6582 nm, c=2.0674 nm and β=90.81° for SbI₃(SC(NH₂)₂)₃ and a=1.4009 nm, b=2.0170 nm, c=2.0397 nm and β=90.84° for BiI₃[SC(NH₂)₂]₃. The infrared spectra reveal that the trivalent antimony or bismuth ion is coordinated by the nitrogen atom, not the sulfur atom of the thiourea. Thermal analysis shows that there are two times structure rearrangements or phase transformation in the complexes from 100 to 170°C.     

Synthesis,characterization, and thermal properties of novel silicon 1,1,3,3-tetramethylguanidinate derivatives and use as single-source chemical vapor deposition precursors

A series of chemical vapor deposition (CVD) precursors have been synthesized by a single-step reaction of 1,1,3,3-tetramethylguanidine and a variety of silicon chlorides. The structures of the 1,1,3,3-tetramethylguanidinate-based compounds were verified by ¹H NMR, ¹³C NMR, XPS, EI-MS, and elemental analysis. The thermal stability, transport behavior, and vapor pressures of these compounds were evaluated by simultaneous thermal analyses (STA). These compounds are highly stable and those in liquid form are very volatile. Silicon carbonitride (SiCN) thin films were prepared by using bis (tetramethylguanidine)-dimethyl-silane as the precursor in helicon wave plasma chemical vapor deposition (HWP-CVD). The properties of the films were investigated by SEM, AFM, and XPS. The results showed that the films have good uniformities, low friction coefficient, and high hardness, enabling the films for fabrication of semiconductor devices.     

Synthesis and characterization of CuInS2 single source precursors for chemical vapor deposition

A family of single source precursors, for the spray chemical vapor deposition (CVD) of chalcopyrite thin films (CuInS₂), has been synthesized in good yields (ca. 65%). Newly synthesized compounds include [{L}₂Cu(SR)₂In(SR)₂], (R=alkyl, aryl; L=neutral donor ligand). The use of the single source precursors provides an attractive alternative over conventionally used multi-source precursors, which are often toxic, air sensitive and pyrophoric. However, it is desirable that these thin films be processed on flexible polymer substrates such as Kapton^TM. Therefore, milder deposition temperatures are needed to maintain the structural integrity of the underlying polymer substrates. By selective manipulation of the steric and electronic properties of the precursor, milder processing temperatures may be employed, while mainting the desired stoichiometry of the deposited films. Elucidation of the structures have been confirmed by the use of NMR. Thermal analytical techniques, differential scanning calorimetry (DSC) and thermogravimetric analysis (TG), have been employed to determine thermal profiles of each candidate compound. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and characterization of antimony trichloride and bismuth trichloride complexes with valine

Two compounds of antimony trichloride and bismuth trichloride with valine are synthesized by solid phase synthesis at room temperature. Their compositions, determined by element analysis, are Sb(C₅H₁₀O₂N)₃·2H₂O and Bi(C₅H₁₀O₂N)₂Cl·0.5H₂O. The crystal structure of antimony complex with valine belongs to triclinic system and its lattice parameters are: a=0.9599 nm, b=1.5068 nm, c=1.9851 nm, α=92.270, β=95.050, γ=104.270. The crystal structure of bismuth complex with valine belongs to monoclinic system and its lattice parameters are: a=1.6012 nm, b=1.8941 nm, c=1.839 nm, β=99.73°. The far-infrared spectra and infrared spectra show that the amino group and carboxyl of valine may be coordinated to antimony and bismuth, respectively, in two compounds. The TG-DSC results also reveal that the complexes were formed.     

新型稀土配合物的合成表征及EXAFS研究

合成了五种新的稀土配合物RE2(NO3)6L2.nH2O, 其中L为一新的含β-双酮和Schiff-base配体, 1, 5-双(1'-苯基-3'-甲基-5'-吡唑啉酮-4')-1-(4'-氨基丁烷-1'-亚胺基)-5-戊酮, RE=Sm, Eu, Gd, Dy, Ho。对配合物进行了质谱、FTIR、变温红外、EXAFS等研究。结果表明: 配合物为双核结构; 配合物中NO3^-以离子型、单齿及双齿同时存在; 配体L中的C=O, C=N及NH2均参与配位; 稀土离子的总配位数为8, 双配位层分别为2个氮和6个氧, RE-N距离在0.230~0.240nm, RE-O0.240~0.250nm。     

Synthesis and characterisation of cyclopentadienyl complexes of barium: precursors for atomic layer deposition of BaTiO3

Cyclopentadienyl complexes Ba(C5Me5)2(THF)2 (1), Ba(C5Me5)2(A) (A = THF, dien, trien, diglyme, triglyme) (2-5), Ba(Pr(i)3C5H2)2(THF)2 (6), Ba(Bu(t)3C5H2)2(THF) (7), Ba(Me2NC2H4C5Me4)2 (8) and Ba(EtOC2H4C5Me4)2 (9) were prepared and characterised with TGA/SDTA, NMR and MS. Crystal structures of 2, 4, 5, 7, 8 and 9 are presented. All complexes prepared sublime under reduced pressure and complexes 1, 6 and 7 showed volatility also under atmospheric pressure. Complexes 1, 6 and 7 lose the coordinated THF when evaporated while complexes 2-5 are sublimable as complete molecules under reduced pressure. Complexes with bulky cyclopentadienyl ligands (6 and 7) are the most thermally stable and volatile among the prepared barocenes. X-ray structure determinations reveal that all the complexes studied are monomeric. Complexes 1, 7 and 8 were successfully tested in BaTiO3 thin film depositions by atomic layer deposition (ALD).     

Synthesis,characterization and thermal behaviour of four homoleptic titanium silanolates

Four titanium silanolates Ti(OSiR₂R′)₄ (1, R = Ph, R′ = ^tBu; 2, R = R′ = Ph; 3, R = R′ = ⁱPr; 4, R = Me, R′ = ^tBu) were synthesised starting from Ti(OⁱPr)₄ and the corresponding silanol, and their thermally induced decomposition was studied. Colourless single crystals of Ti(OSiPh Bu) CHCl C₇H₈ ( CHCl C₇H₈) were obtained from a mixture of chloroform and toluene (1:1) at ?20 °C. The compound crystallizes in the space group R3 c with Z = 18. The metal atom shows an almost ideal tetrahedral coordination, as is demonstrated by the O? Ti? O angles of 108.4(1)–111.1(1)°. Copyright © 2005 John Wiley & Sons, Ltd.     

Alumina-titania oxides: Synthesis and characterization

Alumina-titania mixed oxides with nominal atomic ratios Al/Ti=25 and 2 have been synthesized by cohydrolysis of Al(OsecBu)₃ and Ti(OBu)₄. The oxides were amorphous at 500°C, showing only short range order. Ti was incorporated in alumina in a well dispersed way creating a true Al/Ti mixed oxide. The strength of surface acid sites and specific surface areas were increased at the higher Ti content. The TiO₂ anatase phase was avoided and rutile was formed directly at 900°C.     

Two novel 18-metallacrown-6 complexes: Synthesis,structural characterization and bioactivity

Two new macrocyclic hexanuclear metal(III) 18-metallacrowns-6, [Mn₆(acshz)₆(H₂O)₆] · 18H₂O (1) and [Fe₆(acshz)₆(CH₃OH)₆] · 6CH₃OH · 6H₂O (2), have been synthesized and characterized, where acshz³⁻ is N-acetyl-5-chlorosalicylhydrazidate. These crystal structures contain neutral 18-membered metallacrown rings consisting of six metal(III) ions and six acshz³⁻ ligands. The ring is formed by the succession of six structural moieties of the type [M(III)–N–N] through hydrazide N–N groups bridging the ring metal ions. The ligand enforces the metal ions to form the stereochemistry of a propeller configuration with alternate Λ/Δ or Δ/Λ forms. The largest diameters of the hexanuclear rings are about 6.97 Å at the entrance and 9.53 Å at the centre of the cavity for 1; and 7.94 and 10.24 Å for 2, respectively. The solution integrity and stability of the metallacrowns were confirmed using electrospray ionization ESI-MS and UV–Vis spectroscopy in methanol. Antibacterial screening data indicate the formation of the metallacrown 1 reduces the antimicrobial activity of the ligand H₃acshz hugely, while metallacrown 2 has strong antimicrobial activity against Bacillus subtilis (B. subtilis).     

Synthesis and characterization of β-diketiminato complexes of antimony (III) halides

Treatment of SbX₃ (X = Br, Cl) with DippnacnacLi (Dippnacnac = [{N(C₆H₃ⁱPr₂2,6)C(Me)}₂CH]⁻) or Mesnacnac (Mesnacnac = [{N(Mes)C(Me)}₂CH]⁻, Mes = 2,4,6, trimethyl benzene) affords different products that are dependent on the stoichiometry of the reaction and the halide precursor. When DippnacnacLi is reacted with SbBr₃, C-H activation of the ligand backbone is observed and an asymmetric, bridged bromide dimer is isolated. In comparison, the reaction of SbCl₃ with MesnacnacLi affords monomeric MesnacnacSbCl₂. The solid-state structures were determined using X-ray crystallography.     

Synthesis and characterization of homo- and heterobimetallic niobium and tantalum peroxo-polyaminocarboxylato complexes and their use as single or multiple molecular precursors for Nb-Ta mixed oxides

New water-soluble bimetallic peroxo complexes of niobium^V and/or tantalum^V with high-denticity polyaminocarboxylate ligands have been prepared, characterized from the spectroscopic point of view, and used as molecular precursors for Nb-Ta mixed oxides. Four new homobimetallic complexes, (gu)₃[Nb₂(O₂)₄(dtpaO₃)]·3H₂O 1, (gu)₃[Ta₂(O₂)₄(dtpaO₃)]·5H₂O 2, (gu)₃[Nb₂(O₂)₄(HtthaO₄)]·2H₂O 4 and (gu)₃[Ta₂(O₂)₄(HtthaO₄)]·3H₂O 5 and the corresponding heterometallic complexes, (gu)₃[NbTa(O₂)₄(dtpaO₃)]·2.5H₂O 3 and (gu)₃[NbTa(O₂)₄(HtthaO₄₎]·2H₂O 6 have been obtained. In these compounds, the in situ oxidation of the nitrogen atoms of the PAC ligands into N-oxide groups has been evidenced by IR spectroscopy and mass spectrometry. The thermal treatment of the homonuclear complexes in air at 700 or 800 °C, depending on the Ta content, provided Nb₂O₅ or Ta₂O₅ while the heteronuclear compounds led to the solid solution TaNbO₅. BET and SEM measurements have been carried out and comparison of the morphology of the samples prepared from homo- and heterometallic precursors is discussed.     

Synthesis,characterization and biological screening studies of mixed ligand complexes using flavonoids as precursors

Flavonoids are a group of plant phenolics that provide various health benefits through cell signalling pathways and antioxidant effects. In the present study, a new series of mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) were synthesized by incorporating curcumin and quercetin flavonoid precursors. The structural features of the synthesized complexes were explored using elemental analysis, thermogravimetric analysis, UV–visible, infrared, NMR, mass and electron paramagnetic resonance spectral analyses and conductivity measurements. These data support an octahedral geometry of the synthesized complexes. In silico biological activity score for the ligand was predicted using PASS online software. ADMET properties were studied using VLS3D online software. Anti‐inflammatory and antioxidant activities were experimentally validated which prove that theoretical predictions are in agreement with the experimental results. Interestingly the synthesized complexes interact with calf thymus DNA through groove binding mode. Moreover, they have good potential to cleave pUC19 DNA. Minimum inhibitory concentration values of the synthesized complexes reveal that they have better antimicrobial efficacy than the ligands.     

Synthesis,characterization and properties of some metallophthalocyanine complexes substituted by N -piperidineethanol

The preparation of eight metallophthalocyanine complexes substituted by N-piperidineethanol was achieved by tetramerization of 3-[2-(piperidin-1-yl)ethoxyl] phthalonitrile and 4-[2-(piperidin-1-yl)ethoxyl]phthalonitrile in the presence of a metal salt with n-pentanol as solvent and DBU as catalyst, respectively. These complexes were characterized by IR, elemental analysis, ¹H NMR and mass spectra. Some properties such as UV/visible absorption spectra, rate of singlet oxygen yields, fluorescence spectra and quantum yields were examined and discussed.     

Nanorods of manganese oxides: Synthesis, characterization and catalytic application

Single-crystalline nanorods of β-MnO₂, α-Mn₂O₃ and Mn₃O₄ were successfully synthesized via the heat-treatment of γ-MnOOH nanorods, which were prepared through a hydrothermal method in advance. The calcination process of γ-MnOOH nanorods was studied with the help of Thermogravimetric analysis and X-ray powder diffraction. When the calcinations were conducted in air from 250 to 1050 °C, the precursor γ-MnOOH was first changed to β-MnO₂, then to α-Mn₂O₃ and finally to Mn₃O₄. When calcined in N₂ atmosphere, γ-MnOOH was directly converted into Mn₃O₄ at as low as 500 °C. Transmission electron microscopy (TEM) and high-resolution TEM were also used to characterize the products. The obtained manganese oxides maintain the one-dimensional morphology similar to the precursor γ-MnOOH nanorods. Further experiments show that the as-prepared manganese oxide nanorods have catalytic effect on the oxidation and decomposition of the methylene blue (MB) dye with H₂O₂.