Infrared spectroscopy of closed s-shell gas-phase M+(N2O)n (M = Li,Al) ion-molecule complexes*

ABSTRACT

We present the results of a combined experimental and computational study of the structures of gas-phase M⁺(N₂O)_n (M?=?Li, Al) complexes. Infrared spectra were recorded in the region of the N₂O asymmetric (N?=?N) stretch using photodissociation spectroscopy employing the inert messenger technique. Unlike in our previous studies on M⁺(N₂O)_n (M?=?Cu, Ag, Au and M?=?Co, Rh, Ir) complexes, N– and O–bound isomers in this case are near isoenergetic and are not distinguished spectroscopically at this resolution. In the case of Li⁺ complexes, there is, however, evidence for the presence of bound N₂ moieties, indicating the presence of inserted, OLi⁺N₂(N₂O)_n–type structures. The weak N₂ band lies to the blue of the signature of molecularly N– and O–bound ligands and is well–reproduced in the simulated spectra of energetically low-lying structures computed from density functional theory. No such inserted isomers are observed in the case of Al⁺(N₂O)_n complexes whose infrared spectra can be understood on the basis of molecularly-bound N₂O ligands. The differences in M⁺(N₂O)_n structures observed for these closed–shell, ns², metal centres relative to other metal cations are discussed in terms of the likely bonding motifs.     

Ab initio calculation of the dipole moment of cyanamide

The He(I) photoelectron spectra of the isoelectronic series Fe(CO)₂(NO)₂, Co(CO)₃NO and Ni(CO)₄ are reported and interpreted by means of ab initio SCF-MO calculations. For the nitrosyl complexes it is found that ionization potentials calculated assuming Koopmans' theorem are seriously in error due to the considerably greater orbital relaxation accompanying ionization from metal than from NO valence orbitals. When such allowance is made for orbital relaxation by performing restricted Hartree-Fock (RHF) calculations on the ionic states, the experimental spectra are accurately reproduced and the observed similarity of the spectra of all three molecules is explained.     

Spectroscopic Characterization of Oxime Ligands and Their Complexes

New imine–oxime ligands H₃L¹–H₃L³ have been obtained from reactions of the Schiff base ligands H₂B¹–H₂B³ with monochloroglyoxime. Mononuclear copper(II), cobalt(II), nickel(II), vanadyl(IV) and zinc(II) complexes of the imine–oxime ligands H₃L¹–H₃L³ have been prepared and characterized by elemental analyses, infrared and electronic spectra, magnetic moment and molar conductance data. The molar conductance data show that the complexes are non‐electrolytes. When the imine–oxime ligands react with the metal salts in a 2:1 ratio, they behave as dibasic bidentate ligands towards one metal ion. The nickel(II) and zinc(II) complexes are diamagnetic. The ¹H(¹³C)‐nmr spectra of all ligands and nickel(II) and zinc(II) complexes of the ligands H₃L¹–H₃L³ have been recorded. Mass spectra of the imine–oxime ligands and their nickel(II) and zinc(II) complexes were recorded. Some of the ligands and metal complexes have antibacterial activity.     

Numerical study on characteristics of nitrogen discharge at high pressure with induced plasma

Based on the fluid theory of plasma, a model is built to study the characteristics of nitrogen discharge at high pressure with induced argon plasma. In the model, the spices such as electron, N₂⁺, N₄⁺, Ar⁺, and two metastable states (N₂ (A³∑_u⁺), N₂ (a¹∑_u^-)) are taken into account. The model includes particle's continuity equations, electron's energy balance equation, and Poisson equation. The model is solved with a finite difference method. The numerical results are obtained and used to investigate the effect of time taken to add nitrogen gas and initially-induced argon plasma pressure. It is found that lower speeds of adding the nitrogen gas and varying the gas pressure can induce higher plasma density, and inversely lower electron temperature. At high-pressure discharge, the electron density increases when the proportion of nitrogen component is below 40%, while the electron density will keep constant as the nitrogen component further increases. It is also shown that with the increase of initially-induced argon plasma pressure, the density of charged particles increases, and the electron temperature as well as the electric field decrease.     

Optical CO gas sensing using nanostructured NiO and NiO/SiO2 nanocomposites fabricated by PLD and sol–gel methods

Several kinds of NiO-based nanostructured films were prepared by pulsed-laser deposition (PLD) and sol–gel method, and CO sensing properties (1%, balanced by N₂) of these films were studied. The sensitivity, defined as a difference of optical transmittance by gas atmospheric change (T=T(CO)-T(air)), increased with increasing NiO content for the sol–gel prepared films, and increased with the film thickness for the laser deposited NiO films. Sol–gel films exhibited shorter response time than NiO films prepared by PLD under low Ar pressure of 6.7×10^-2 Pa indicating a better gas permeability. A shorter response time was also obtained upon raising argon pressure from 6.7×10^-2 Pa to 8.0 Pa during laser ablation due to the morphological change. Covering a NiO film even with a very thin (0.8 nm) layer of SiO₂ by sputtering drastically reduced the CO sensitivity. The multilayered NiO/SiO₂ films were substantially less sensitive to the CO gas than NiO films due to the same reason. Sensing mechanism of the NiO films is due to catalytic CO oxidation that reduces the concentration of adsorbed O₂ species and results in optical transmittance increase upon change in the environment from air to CO. PACS 81.15.Fg; 81.20.Fw; 83.85.Gk     

Particular features of the ν(OH) absorption band of strongly hydrogen-bonded complexes in the gas phase,low-temperature matrices,and crystalline films at 12–600 K

The particular features of the ν(OH) absorption band of dimers with a strong hydrogen bond (ΔH = 24–50 kcal/mol = 8000–17000 cm^?1/molecule) formed by molecules of phosphinic acids R₂POOH N₂ are studied in the gas phase, low-temperature argon and nitrogen matrices, and crystalline films. It is found that, irrespective of the type of the acid, the ν(OH) IR absorption bands of dimers are broad (Δν_1/2 ～ 1000 cm^?1) and similar in shape, exhibiting a characteristic ABC structure. The formation of these anomalously broad absorption bands is shown to be primarily associated with vibrations of the ?POOH fragments, participating in the hydrogen bonding. A change in the temperature in the range 12–600 K and the passage from cyclic dimers in the gas phase to helical chains with hydrogen bonds in the crystalline state cause no significant changes in the shape, width, or structure of the dimer band. The contribution to the formation of the broad absorption band of the (R₂POOH)₂ dimers made by anharmonic interactions between the high-frequency ν(OH) vibration and the low-frequency intermolecular vibrations is estimated. The absorption spectra of weak complexes R₂POOH...N₂ in matrices at 12 K are discussed.     

X-ray photoelectron spectroscopic observation of nitrogen-containing gases adsorbed at high pressures on some transition metals

The chemisorbed species formed by reaction of nitrogen-containing gases (NO, N₂O, N₂ and dry air) on some transition metals (Ni, Cu, Ti, Co and Pd) at high pressures (1–200 torr) are examined by XPS. At least four adsorption species are observed on the surface at ambient temperature. They can be assigned to ?NO₃ (407.3 eV), ?NO₂ (404.5 eV), ?NO (400.0 eV) and the nitrogen bound directly to metal, which shows a characteristic energy value for each metal. This feature differs from the reported results of low pressure adsorption experiments. Relative abundances among the chemisorbed species vary with individual metals and gases.     

Carbon-13 NMR Spectra of Some Group VIIB Transition Metal Thiocarbonyl and Selenocarbonyl Complexes

Recently, we reported the discovery of the first examples of transition metal selenocarbonyl complexes, (n⁵-C₅H₅) Mn (CO)₂ (CSe) and (n⁶-C₆H₅CO₂CH₂(CO)₂ (CSe).¹ These complexes are particularly interesting because, unlike CO and CS, the diatomic CSe molecule has so far eluded isolation even at very low temperatures,² and so these complexes represent the stabilization of a chemically unstable species through coordination to a metal (cf. metal carbene complexes). We have also synthesized several thiocarbonyl complexes of the same type,^3,4 as well as the analogous rhenium selenocarbonyl complexes.⁴ While many detailed studies of the ¹³C nmr spectra of transition metal carbonyls have appeared in the literature over the past few years, there have been no such studies for the closely related thiocarbonyls and selenocarbonyls, although a few isolated data have been reported recently for metal thiocarbonyls.^5,6 In this communication, we report the ¹³C nmr spectra of the isoelectronic series of complexes, (n⁵-C₅H₄R) M(COI)₂ (CX) (M = Mn, R = H, CH₃; M = Re, R = H; X = O,S, Se).     

The effect of inactive impurities on a surface in NO-CO reaction: A Monte Carlo simulation

The interaction among the reacting species in the NO-CO reaction on a metal catalytic surface that proceeds according to the Langmuir-Hinshelwood thermal mechanism is studied by means of Monte Carlo simulations. The study of this system is essential for the understanding of the influence of impurities on the catalytic oxidation of NO by CO. It is found that this complex system exhibits irreversible phase transitions between active states with sustained reaction and poisoned states without reaction. The same system has also been investigated by non-thermal (Eley-Rideal) mechanism. Both the phase diagrams of the surface coverage and the steady state production of CO₂ and N₂ are evaluated as a function of the partial pressures of the reactants in the gas phase. From this study, it is observed that with the increase of impurities, the production rate reduces and the reaction stops at a certain point. Moreover, the first order transition in the phase diagram converts into second order phase transition that is in accordance with the experimental findings. Therefore, the first order phase transition, which is a characteristic of such catalytic reactions, is eliminated.     

The electronic structure of dinuclear transition-metal complexes containing metal—metal interactions: II. He(I) and He(II) photoelectron spectra of hexacarbonyldi-irondisulfur and related complexes

The He(I) and He(II) photoelectron spectra of a series of Fe₂(CO)₆LL¹-type complexes (L = L¹ = S, (i-propyl)S; L,L¹ = t-but of an all-electron, ab initio SCF MO calculation on Fe₂(CO)₆S₂ and of extended CNDO calculations on related molecules. Assignments given ar He(I)/He(II) intensity differences, and on comparison with related molecules.The coordination of the bridging ligands to the metal centres and the nature of the metal—metal interactions are discussed.     

Synthesis and Characterization of New Cationic Fe(III),Co(II) and Ni(II) Complexes Containing Isatin/Triphenylphosphine Mixed Ligands

New cationic Fe(III),Co(II) and Ni(II) mixed ligand complexes containing both triphenylphosphine and isatin ligands were prepared and characterized using conventional physical and chemical methods of analysis

(I.R., UV-Vis., and ¹H NMR). Microanalytical data of the investigated complexes are consistent with the formulations. [Fe(Isa)₂ {P(Ph)₃}₂]³⁺, [Co(Isa)₂ {P(Ph)₃}₂]²⁺ and [Ni(Isa)₂ {P(Ph)₃}₂]²⁺, (Where Isa = Isatin and P(Ph)₃ = Triphenylphosphine).

The prepared complexes are soluble in polar solvents and could be of potential use in bio-inorganic applications.     

Excitation transfer and quenching induced in inelastic collisions of cadmium 51P1 atoms

The quenching of excited Cd(5¹P₁) atoms induced in collisions with Ar, N₂, H₂, CO, and CO₂ has been investigated using methods of fluorescence spectroscopy. Mixtures of Cd vapor and quenching gases contained in a quartz cell were irradiated with 2288 Å resonance radiation and the fluorescence spectrum consisting of the 2288 Å direct component, as well as of the 3261 Å sensitized component, was monitored in relation to the gas density. The experiments yielded the following cross sections Q_tot for the overall collisional deexcitation of the ¹P₁ state, as well as the cross sections Q₁₃ for ¹P₁→³P_J excitation transfer (in Ų).For argon: Q₁₃ < 2 × 10^-2, for N₂: Q_tot =48.5, Q₁₃ =48.0; for H₂: Q_tot = 19, Q₁₃ = 7.2; for CO: Q_tot = 110, Q₁₃ = 15; for CO₂: Q_tot = 121, Q₁₃ < 6 × 10^-3.     

非故意掺杂GaN薄膜方块电阻与载气中N2比例关系研究

利用金属有机气相外延方法研究了非故意掺杂GaN薄膜的方块电阻与高温GaN体材料生长时载气中N₂比例的关系.研究发现,随着载气中N₂比例的增加,GaN薄膜方块电阻急剧增加.当载气中N₂比例为50%时,GaN薄膜方块电阻达1.1×10⁸Ω/□,且GaN表面平整,均方根粗糙度为0.233nm.二次离子质谱分析发现,载气中N₂比例不同的样品中碳、氧杂质含量无明显差别.随着载气中N₂比 关键词： 半绝缘GaN薄膜 载气 金属有机气相外延 位错     

The effect of NO/O2 ratio in NO-CO-O2 reaction on a catalytic surface: A computer simulation study

The interaction among the reacting species in the NO-CO-O₂ reaction on a metal catalytic surface that proceeds according to the Langmuir-Hinshelwood mechanism is studied by means of Monte Carlo simulation. The study of this three-component system is essential for the understanding of the influence of NO/O₂ ratio on the catalytic reduction of NO into N & O and oxidation of CO to CO₂. It is found that this complex system, which has not been studied on these lines before, exhibits irreversible phase transitions between active states with sustained reaction and poisoned states with the catalytic surface fully covered by the reactants. The phase diagrams of the surface coverage with CO, N or O and the steady state production of CO₂ are evaluated as a function of the partial pressure of CO in the gas phase. From this study, it is observed that with the addition of NO in the CO-O₂ reaction, the critical points in the phase diagram move towards lower values of CO partial pressure but the width of reaction window remains almost the same. However, the maximum production rate of CO₂ decreases continuously. On the other hand, the addition of O₂ in the NO-CO reaction shifts the critical points towards higher values of CO pressure. Moreover, the width of reaction window as well as the production rate of CO₂ increases with the increase in O₂ concentration.     

Conditional statistics of inert droplet effects on turbulent combustion in reacting mixing layers

Direct numerical simulation (DNS) of turbulent reacting mixing layers laden with evaporating inert droplets is used to assess the droplet effects in the context of the conditional moment closure (CMC) for multiphase turbulent combustion. The temporally developing mixing layer has an initial Reynolds number of 1000 based on the vorticity thickness with more than 16 million Lagrangian droplets traced. An equivalent mixture fraction incorporating the inert vapour mass fractions clearly demonstrates the effects of vapour dilution on the mixture. Instantaneous fields and conditional statistics, such as the singly conditioned scalar dissipation rate, the gas temperature 〈 T _g|η 〉, conditional variance of the gas temperature 〈 T _g ^”2|η 〉 and conditional covariance between the fuel mass fraction and gas temperature 〈 Y _f ^” T _g ^”|η 〉 show considerable droplet effects. Comparison between the droplet-free and droplet-laden reacting mixing layer cases suggests significant extinction in the latter case. The resulting large conditional fluctuations around the conditional means contradict the basic assumption behind the first-order singly conditioned CMC. More sophisticated CMC approaches, such as doubly conditioned or second-order CMCs are, in principle, better able to incorporate the effects of evaporating droplets, but significant modelling challenges exist. The scalar dissipation rate doubly conditioned on the mixture fraction and a normalized gas temperature 〈 χ | η, ζ 〉 exemplifies the modelling complexity in the CMC of multiphase combustion.     

Controlling spin off state by gas molecules adsorption on metal-phthalocyanine molecular junctions and its possibility of gas sensor

Employing Green's function (GF) technique in combination with spin-polarized density functional theory (DFT), we study the electronic structure and magnetic properties of metal phthalocyanine (MPc) (M?=?Mn, Fe, Co, Ni, Cu, Zn) with or without four different gas molecules (NO, CO, O₂ and NO₂) adsorbing on the M atom of MPc molecule. The corresponding stable adsorption structural configurations and transport properties of MPc molecular junctions are also investigated. Our results indicate that the magnetic moment of MPc for M?=?Mn, Fe and Co can be modified by the specific gas molecule adsorption, which is mainly ascribed to competitive relation of HOMO-LUMO Gap and Hund's rules. However, for M?=?Ni, Cu and Zn, it is difficult to detect gas molecule because the interaction of M atom and these gases is most of weak van der Waals interaction. Remarkably, the spin of MPc molecule can be switched to a magnetic off-state by specific gas absorption, giving rise to a potential application on controllable spintronic devices. In addition, CO, NO, O₂ and NO₂ gas molecules can be detected selectively by measuring spin filter efficiency of these MPc molecular junctions. On the basis of our results, MPc (M?=?Mn, Fe, Co) molecular junctions can be considered as a promising nanosensor device to detect individual gas molecules.     

ESR and Chemical Bonding of Some Copper Complexes

ESR spectra of copper (II) was measured in 33 copper complexes which were synthesized in this laboratory and the bonding parameter α²of copper was calculated according to the method proposed by Kivelson. ⁽¹⁾ The results of these calculations are classified, together with the data quoted from the literature,^1-5into four groups according to the kinds of ligand atoms, i.e., α²is 0.72 to 0.87 for 0₄ - type complexes, 0.69 to 0.86 in N₂O₂, 0.74 to 0.82 in N₄, and 0.54 to 0.62 in S₄ and S₂₃N₂ type complexes, where 0, H and S refer the oxygen, nitrogen and sulfur atoms of ligands, respectively, that directly coordinate with copper.     

The reactions of NO with diesel soot, fullerene, carbon nanotubes and activated carbons doped with transition metals

This work investigates the reactions of NO with eight different types of carbon particles: activated pinewood charcoal, activated charcoals doped with iron, nickel, copper or platinum nitrates, fullerene, carbon nanotubes and soot produced from a heavy duty diesel engine. For this mixtures of NO and argon were passed through a fixed bed of carbonaceous particles mixed with quartz sand, held at a temperature between 25 and 850 °C. The concentrations of CO, CO₂, NO, NO₂ and N₂O in the off-gases were measured; the concentration of N₂ was inferred by atomic balance. The balance on atomic oxygen closed well for all the materials studied. The results are discussed in terms of an elementary reaction mechanism; estimates are made of apparent activation energies for the overall reactions forming CO and CO₂.     

NO--CO--O2 Reaction on a Metal Catalytic Surface using Eley--Rideal Mechanism

Interactions among the reacting species NO, CO and O2 on metal catalytic surfaces are studied by means of Monte Carlo simulation using the Eley-Rideal （ER） mechanism. The study of this three-component system is important for understanding of the reaction kinetics by varying the relative ratios of the reactants. It is found that contrary to the conventional Langmuir-Hinshelwood （LFI） thermal mechanism in which two irreversible phase transitions are obtained between active states and poisoned states, a single phase transition is observed when the ER mechanism is combined with the LH mechanism. The phase diagrams of the surface coverage and the steady state production of CO2, N2 and N2O are evaluated as a function of the partial pressures of the reactants in the gas phase. The continuous production of CO2 starts as soon as the CO pressure is switched on and the second order phase transition at the first critical point is eliminated, which is in agreement with the experimental findings.     

Complexability of o-bisguanidinobenzenes with arsenic and phosphoric acids in solution and solid states, and the potential use of their immobilized derivatives as solid base ligands for metal salts and arsenic acid

The role of o-bisguanidinobenzenes (BGBs) as new Brønsted base ligands for arsenic and phosphoric acids was examined. In solution state, complexation was evaluated by Job’s plot in ¹H NMR experiment, indicating a 1:1 complex formation, whereas in solid state crystalline structures of complexes obtained were addressed by X-ray crystallographic analysis and/or solid state ¹³C NMR experiment, in which 1:2 complexes between the BGB and the acid components were normally formed. Based on these results, Merrifield and Hypogel^® resin-anchored BGBs were designed and prepared as the corresponding polymer-supported host ligands. Evaluation of their coordination ability with metal salts (ZnCl₂ and CoCl₂) and arsenic acid in aqueous media by ICP-MS showed that the latter Hypogel^® resin-anchored BGBs acted as effective immobilized base ligands.