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1.
TiCl 4(THF) 2 was impregnated by spin-coating on a Si(1 0 0) wafer covered with a thin SiO x layer and on a polycrystalline Au foil. The nature of the surface species was determined at room temperature and after annealing, by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). A mixed Si:O:Ti interfacial layer was formed on the silicon substrate while in the case of Au, TiOCl x and TiO x were the main surface species at room temperature. Annealing at 723 K leads to the total desorption of the Cl atoms, and in both cases a significant amount of Ti atoms was reduced to the Ti 3+ state. AFM measurements revealed a homogenous distribution of nano-sized TiO x clusters with semi-ellipsoid shape and increased contact area with the underlying silica. 相似文献
2.
The accuracy of n-mode representations of potential energy surfaces (PESs) is investigated, for a reaction involving six degrees of freedom. Probabilities computed with the time-dependent wave packet (TDWP) method for reaction of ( v = 0,1; j = 0) H 2 on Pt(1 1 1) employing a 5-mode (4-mode) PES show quantitative (semi-quantitative) agreement with results for the full PES. The ratio of the v = 1 and v = 0 reaction probabilities obtained with the 5-mode PES is in quantitative agreement with full PES results for most of the energy range considered. The results suggest that n-mode representations can be employed successfully to study reactions of polyatomic molecules with surfaces. 相似文献
3.
The stability and electronic properties of highly packed 1-hexyl-naphthalene (HNap) molecular wire on Si(0 0 1) have been studied with first principles DFT method. HNap assembles into a 1D arrangement on the Si(0 0 1)[2 × 1] surface on which molcules adopt a commensurate structure along a dimer row with an intermolecular distance of 3.8 Å. HNap is attached to the surface through the hexyl chain, and stands normal to the surface. This highly packed structure leads to the formation of delocalized π-orbitals over the entire wire but essentially localized on the naphthalene counterpart, and well separated from the Si surface states. Cohesion energy within the wire arises from a significant attraction between hexyl chains, and to a weaker stabilizing π–π interaction between naphthalenes. 相似文献
4.
Arrays of extremely long and perfectly parallel mesoscopic Pb-wires are formed and studied in UHV conditions. Au-modified Si(5 3 3) substrate modified by deposition of sub-monolayer amount of Au are used as templates. A uniform distribution of monoatomic steps and terraces on well-oriented Si(5 3 3) is induced by formation of Au-chains running along step edges. Real-time surface imaging with LEEM shows that the wires growing on substrates held at temperatures close to the room temperature are all aligned parallel to
azimuth, along the step edges. After nucleation of elongated islands, the 1 ML thick wetting layer remains on the vicinal Si surface. RHEED and low-temperature STM experiments show that the wires have triangular cross-section, limited by (1 1 1) and (1 0 0) facets of Pb. The width of the wires is 60 nm, whereas their length is up to 8 μm. The observed growth anisotropy leading to the formation of mesoscopic wires is attributed to enhanced one-dimensional diffusion along the parallel grooves and trenches that form vicinal surfaces. An additional factor, contributing to the anisotropic growth, is probably the anisotropic strain, due to the large misfit between Pb and Si lattices. 相似文献
5.
Adsorption dynamics experiments on Cu(1 0 0) at 300 K indicate that surface defects induced by 3.4 keV Ar +-ion bombardment strongly enhance the dissociative chemisorption probability of O 2. Energy selective molecular beam surface scattering experiments reveal a defect induced low-barrier dissociation pathway leading to enhanced dissociation of O 2 molecules with translational energy up to 60 meV. Density functional theory calculations attribute the decrease in O 2 dissociation barrier to the weakening of O–O bond at Cu vacancies, thus resolving the contradiction between experimental observations and theoretical predictions of the height of the barrier to O 2 dissociation on Cu(1 0 0). 相似文献
6.
The bimetallic [Pt(NH 3) 4] 2[W(CN) 8][NO 3]·2H 2O is characterised by single-crystal X-ray diffraction [S.G. P2 1/ m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1) * separations of 4.77(2), 4.55(2) * and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO 3− between parallel [Pt(1)(NH 3) 4] 2+ planes and the second consists of [W(CN) 8] 3− interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH 3) 4] 2+. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH 3 ligands, water molecules and oxygen atoms of NO 3− counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer. 相似文献
7.
Hafnium β-diketonatochlorides HfCl 2(thd) 2 (1), HfCl(thd) 3 (2) as well as β-diketonato-silylamide and/or siloxide derivatives of 1 namely Hf(thd) 2[N(SiMe 3) 2] 2 (3), Hf(thd) 2(OSiMe 3) 2 (4) and Hf(thd) 2(OSi tBuMe 2) 2 (5) (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) were synthesized and characterized by elemental analysis, FT-IR, 1H NMR and TGA. 2 and 5 were also characterized by single-crystal X-ray diffraction. The siloxide ligands are in cis position for 5 and exert a strong trans effect. The new volatile compounds were tested as single-source precursors for the deposition of HfSi xO y films by pulsed liquid injection MOCVD on Si(1 0 0) and R plane sapphire. The as-deposited at 600–800 °C films were essentially amorphous, Hf-rich (Hf/Hf + Si = 0.7–0.85) and smooth. 相似文献
8.
Perovskite thin films with a nominal composition of La 0.6Ca 0.4Mn 1−xFe xO 3 ( x = 0, 0.2) were deposited by pulsed reactive crossed beam laser ablation. The film properties, such as electrical conductivity and magnetoresistance are studied as a function of the oxygen content and substrate type. The oxygen content of the thin films was determined by Rutherford Backscattering and controlled by varying the background gas pressure, pressure of the gas pulse and by using alternatively O 2 and N 2O as the gas pulse. LaAlO3 and SrTiO3 were used as substrates at deposition temperature of 650 °C. The grown films were analyzed by X-ray diffraction in order to optimize the growth conditions, i.e. to obtain epitaxial thin films. Thin films doped with 20% Fe were grown under the same experimental conditions as the undoped LCMO films and the effect of the doping on the structural and transport properties of the thin films has been investigated. The temperature of the metal–insulator transition was measured as a function of the oxygen content and substrate type. 相似文献
9.
The title cobalt(III) complexes have been investigated by polarized absorption and Raman spectroscopies of the single crystals. The symmetry properties of the d-electron orbitals and of the vibrational modes attributable to the Raman bands of trans(Cl 2)-[CoCl 2(NH 3) n(H 2O) 4−n]Cl complexes ( n = 2, 3, or 4) were examined to elucidated the peculiar observation that ligand substitution causes no splitting of the 15 200-cm −1 absorption band and the 250-cm −1 Raman band. Effects of replacing the NH 3 ligand with H 2O on the electronic structure, atom–atom force constants and vibrational modes of these complex ions are briefly described. 相似文献
10.
A coordination polymer was synthesized by the reaction of CoCl 2 with 1,2,4-triazole-5-one (TO) and charaterized by means of IR and TG–DTG. Single-crystal structure analysis showed that the complex crystallized in the monoclinic space group C2/ c: a = 23.105(9) Å, b = 3.5683(2) Å, c = 13.589(6) Å, = 90°, β = 124.038(4)°, γ = 90°, V = 928.4(7) Å 3, Z = 4. The standard molar enthalpy of formation of the complex was determined to be (−1034.28 ± 0.95) kJ mol −1. 相似文献
11.
采用分子束外延法分别在650-920℃的Si(110)和920℃的Si(111)衬底表面生长出铁的硅化物纳米结构,并主要分析了920℃高温下纳米结构的形貌、组成相及其与Si衬底的取向关系.扫描隧道显微镜(STM)研究表明,920℃高温下,Si(110)衬底上生长的铁硅化合物完全以纳米线的形式存在,且其尺寸远大于650℃低温下外延生长的纳米线尺寸;Si(111)衬底上生长出三维岛和薄膜两种形貌的铁硅化合物,其中三维岛具有金属特性且直径约300 nm、高约155 nm,薄膜厚度约2 nm.电子背散射衍射研究表明920℃高温下Si(110)衬底上生长的纳米线仅以β-FeSi2的形式存在,且β-FeSi2相与衬底之间存在唯一的取向关系:β-FeSi2(101)//Si(11 1);β-FeSi2[010]//Si[110];Si(111)衬底上生长的三维岛由六方晶系的Fe2Si相组成,Fe2Si属于164空间群,晶胞常数为a=0.405 nm,c=0.509 nm;与衬底之间的取向关系为Fe2Si(001)∥Si(111)和Fe2Si[1 20]//Si[112]. 相似文献
12.
Effects of substituents on cyclopentadienyl group for homopolymerization of ethylene, 1-hexene, and for ethylene/1-hexene copolymerization using a series of nonbridged (cyclopentadienyl)(ketimide)titanium complexes of the type, Cp′TiCl 2(N=C tBu 2) [Cp′ = Cp (1), tBuC 5H 4 (2), C 5Me 5 (Cp *, 3), and indenyl (4)] have been explored in the presence of methylaluminoxane (MAO) cocatalyst. Complexes 1–3 showed the similar catalytic activities for ethylene polymerization although the activity by 4 was somewhat low, whereas the activity for 1-hexene polymerization increased in the order 1 > 4 2 > 3. These complexes showed significant activities for ethylene/1-hexene copolymerization affording high molecular weight poly(ethylene- co-1-hexene)s with unimodal molecular weight distributions, and the activity increased in the order: 4 > 1 2, 3. The rErH values in the polymerization by 1–3 at 40 °C were 0.35–0.52 which clearly indicate that the 1-hexene incorporation in the copolymerization did not proceed in a random manner. The rE values by 1–3 were 6.0–6.4 and the values were independent upon the cyclopentadienyl fragment employed; the rE values by 4 at 40 °C were 10.2–10.9 which were close to those by ansa-metallocene complex catalysts. These values were influenced by the polymerization temperature, and the 1-hexene incorporation by 1–4 became inefficient at higher temperature, although the observed activities especially by 1, 4 were highly remarkable. 相似文献
13.
The X-ray crystal structure of an anionic octacoordinate Eu 3+ complex of the formula K 12H 8[Eu 4(EDTMP) 4] · 45H 2O, where EDTMP is the ethylenediaminetetra(methylenephosphonate) anion, hereinafter referred to as I, has been determined. The crystal consists of cyclic tetrameric complex anions, in which the surrounding of each Eu 3+ ion is composed of two nitrogen atoms and six oxygen atoms from phosphonate groups. One of the phosphonate groups in the ligand molecule is tridentate ( O: O′, O″), thus giving rise to the formation of the tetramers. The compound was characterized by UV–Vis electronic spectroscopy. At room and liquid nitrogen temperatures the complex shows luminescence from both 5D 0 and 5D 1 states, the latter one, which is very rare in Eu 3+ compounds with organic ligands, is probably brought about by the saturation of the coordination sphere with the phosphonate groups. 相似文献
14.
Temperature dependence studies of adsorption of sulfuric acid species on Pt(1 1 1) and Au(1 1 1) electrodes were carried out using in situ infrared reflection absorption spectroscopy. A temperature-dependent shift of the interconversion potential between HSO 4−/H 3O + and H 2SO 4 on a Pt(111) electrode was observed. A temperature-dependent frequency shift of the absorption bands of HSO 4− was also observed on both Pt(1 1 1) and Au(1 1 1) electrodes in the potential region where a √3×√7 structure evolved. Modelling experiments in ultrahigh vacuum revealed that ordering of the overlayer water molecules played an important role in the frequency of the absorption bands of HSO 4−. 相似文献
15.
The preparation, spectroscopic characterization and magnetic study of N, N′-bis(substituted-phenyl)oxamidate-bridged nickel(II) dinuclear complexes of formula {[Ni(N 3-mc)] 2(μ-CONC 6H 4-X)}(PF 6) 2 (N 3-mc = 2,4,4-trimethyl-1,5,9-triazacyclo-dodec-1-ene (Me 3-N 3-mc) or 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene (Me 4-N 3-mc), X = 2-Cl, 4-Cl, 2-OCH 3, 4-OCH 3) are reported. These paramagnetic nickel(II) complexes have been characterized by both one- and two-dimensional (COSY) 1H NMR techniques. The COSY spectrum of 5 has allowed to achieve the assignment of the phenyl protons of the N, N′-diphenyloxamidate. The crystal structures of [Ni(Me 3-N 3-mc)(μ-CONC 6H 4-4-Cl)] 2(PF 6) 2 (6), [Ni(Me 3-N 3-mc)(μ-CONC 6H 4-4-OMe)] 2(PF 6) 2 (8) and [Ni(Me 4-N 3-mc)(μ-CONC 6H 4-2-Cl)] 2(PF 6) 2 (9) have been determined and their magnetic properties have been studied. The value of magnetic coupling between the two nickel(II) ions across the oxamidate bridge [ J = − 37.6 (6), −39.9 (8) and −39.7 cm −1 (9)] is sensitive to the distortion of the coordination sphere of the metal ions and the topology of the molecular bridge. 相似文献
16.
Infrared and Raman spectra for metal–string complexes M 3(dpa) 4X 2 (M = Ni, Co, dpa = di(2-pyridyl)amido, and X = Cl, NCS) are studied. We assign the Ni 3 asymmetric stretching vibration to infrared lines at 304 and 311 cm −1 for Ni 3(dpa) 2Cl 2 and Ni 3(dpa) 2(NCS) 2, respectively. A Raman shift at 242 cm −1 is assigned to the Ni 3 symmetric stretching mode. For Co 3 complexes a line for the Co 3 asymmetric stretching mode appears at 313 and 331 cm −1 for Co 3(dpa) 2Cl 2 and Co 3(dpa) 2(NCS) 2, respectively. 相似文献
17.
The ruthenium(II) complex Ru(CO) 2(NH 2(NH 2CH 2C 6H 5) 2(Si(C 6H 5)(CH 3) 2)I has been prepared by the reaction of Ru(CO) 4(Si(C 6H 5)(CH 3) 2)I with benzylamine. Two-dimensional homonuclear 1H NMR experiments examine the scalar coupling of the enantiotopic amino and methylene protons of the benzylamine ligand. X-ray analysis of Ru(CO) 2(NH 2CH 2C 6H 5) 2(Si(C 6H 5)(CH 3) 2)I·1/3C 5H 12 (triclinic; P
; a = 14.266(4), b = 15.748(5), c = 20.082(6) Å; = 94.38(3), β = 96.30(2), γ = 101.52(2)°) indicates three crystallographically unique complexes form a clathrate with a pentane guest. 相似文献
18.
Zwitterionic titanoxanes {Cp[ η5-C 5H 4B(C 6F 5) 3]Ti} 2O (I) and {( η5- iPrC 5H 4)[ η5-1,3- iPrC 5H 3B(C 6F 5) 3]Ti} 2O (II), which contain two positively charged Ti(IV) centres in the molecule, are able to catalyse the ring-opening polymerization of -caprolactone (-CL) in toluene solution and in bulk. The process proceeds with a noticeable rate even at room temperature and accelerates strongly on raising the temperature to 60 °C. The best results have been obtained on carrying out the reaction in bulk. Under these conditions, the use of I as a catalyst (-CL:I = 1000:1) gives at 60 °C close to quantitative yield of poly--CL with the molecular mass of 197 000. An increase in the -CL:I ratio to 6000:1 increases the molecular mass of poly--CL to 530 000. Tetrahydrofuran (THF) is also polymerized under the action of I albeit with a lesser rate. However, the molecular mass of the resulting poly-THF can reach rather big values under optimal conditions (up to 217 000 at 20 °C and the THF:I ratio of 770:1). A rise in the reaction temperature from 20 to 60 °C results here to a decrease in the efficiency of the process. Titanoxane II is close to I in its catalytic activity in the -CL polymerization but it is much less active in the polymerization of THF. Propylene oxide (PO), in contrast to -CL and THF, gives with I only liquid oligomers in wide temperature and PO:I molar ratio ranges (−30 to +20 °C, PO:I = 500–2000:1). γ-Butyrolactone and 1-methyl-2-pyrrolidone are not polymerized under the action of I at room temperature. The reactions found are the first examples of catalysis of the cationic ring-opening polymerization by zwitterionic metallocenes of the group IVB metals. 相似文献
19.
The solid–liquid equilibria of the ternary system H 2O–Fe(NO 3) 3–Co(NO 3) 2 were studied by using a synthetic method based on conductivity measurements. Two isotherms were established at 0 and 15 °C, and the stable solid phases which appear are the iron nitrate nonahydrate (Fe(NO3)3·9H2O), the iron nitrate hexahydrate (Fe(NO3)3·6H2O), the cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and the cobalt nitrate trihydrate (Co(NO3)2·3H2O). 相似文献
20.
Several complexes of 2-(indazol-1-yl)-2-thiazoline (TnInA) with the divalent ions Co and Zn have been synthesized by the direct combination of the ligand and the metal chloride or nitrate hydrated salts in ethanol. These complexes have been characterized by a variety of physical–chemical techniques. Moreover, the structures of [CoCl 2(TnInA) 2] · C 2H 6O (1) and [(M)(TnInA) 2(H 2O) 2](NO 3) 2 (M = Co, 3; Zn, 4) were determined by single-crystal X-ray diffraction. In all the complexes, the ligand TnInA bonds to the metal ion through the indazole and thiazoline nitrogen atoms. In complex 1 the environment around the cobalt ion may be described as a distorted octahedron with two TnInA ligands and two chlorine ligands. Compounds 3 and 4 are isostructural with a distorted octahedral geometry around the metal center, being linked to two water molecules and two TnInA ligands. However, in complex [ZnCl 2(TnInA)] (2) the zinc atom is four-coordinated with a probable tetrahedral environment with two chloro ligands and one TnInA ligand bonded to the metal ion. 相似文献
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