The structures of some trimers of carbon monoxide—An infrared matrix isolation spectroscopic and ab initio molecular orbital study

Using a number of potential models for the gas-phase structure of the trimer of carbon monoxide as a guide, ab initio molecular orbital calculations have been carried out on this aggregate in order to determine its probable structure and vibrational spectrum in cryogenic matrices. The Fourier transform infrared spectra of carbon monoxide trapped in argon and nitrogen matrices have been recorded and, on the basis of the results of the theoretical calculations, a search for possible absorptions which may be assigned to trimeric species has been undertaken.     

The interaction of formohydroxamic acid with carbon monoxide: FTIR matrix isolation and quantum chemistry studies

Argon matrix infrared spectra of the complexes formed between formohydroxamic acid (HCONHOH) and carbon monoxide have been recorded. The experimental results indicate formation of three isomeric complexes. In two complexes the NH or OH groups of formohydroxamic acid are attached to the carbon atom of the CO molecule and in the third complex the NH group interacts with the oxygen atom of CO. The formohydroxamic acid complex with two CO molecules is also trapped in the matrix. One of the two CO molecules interacts with the NH group and the second one with the OH group of HCONHOH, in both cases the site of interaction is the carbon atom of CO. Theoretical studies of the structure and spectral characteristics of the complexes were carried out on the DFT(B3LYP)/6-311++G(2d,2p) level. The calculated vibrational frequencies for the complexes present in the matrices are in good agreement with the experimental data. The calculations show also an additional potential energy minimum corresponding to the complex in which the OH group of formohydroxamic acid is attached to the oxygen atom of carbon monoxide.     

Tetrabromocyclopentadienylidene: generation and reaction with CO in low temperature matrices

The photolysis of tetrabromodiazocyclopentadiene (1) in low temperature argon matrices generates the carbene, tetrabromocyclopentadienylidene (2), for which both ir and uv-visible absorptions have been recorded. In argon matrices doped with carbon monoxide or in pure carbon monoxide matrices, the carbene reacts with CO giving the ketene, tetrabromofulvenone (4). The carbene did not show any tendency to dimerize at temperatures up to the point where matrix boil-off occurred.     

Reactivity of atomic gold anions toward oxygen and the oxidation of CO: experiment and theory

Results for the binding of carbon monoxide and oxygen along with the oxidation of CO in the presence of atomic Au(-) have been obtained utilizing a fast-flow reactor mass spectrometer. In addition, density functional calculations have been performed to explain the experimental findings. It was observed that upon oxygen addition to the metal plasma, gold oxide species of the form AuO(n)(-), where n = 1-3, were produced. The addition of carbon monoxide to the preoxidized gold atom revealed that AuO(-) and AuO(3)(-) promote the oxidation of CO. Density functional calculations on structures and their energetics confirmed the experimental findings and allowed us to propose mechanisms for the oxidation of carbon monoxide. The reactions of CO with AuO(1,3)(-) proceed via complex formation with CO bound to the oxygen atom, followed by either cleavage of the Au-O bond or complex rearrangement to form a weakly bound CO(2) unit, leading in both cases to the emanation of CO(2).     

Matrix and ab initio infrared spectra of germanium carbonyls

Germanium monocarbonyl has been prepared by high-temperature vaporization of Ge with excess carbon powder or CO co-condensation and trapped in various matrices at 12 K. Fourier transform infrared spectra, ab initio (MP2 and CISD) and density function (Becke3LYP) calculations suggested a linear species with the formula GeCO. A weak feature appearing only in annealed N₂ and CO matrices containing GeCO has tentatively been assigned to germanium dicarbonyl on grounds of isotopic substitution and theoretical calculations. SCF and CI methods predict a bent structure for this complex.     

Electrophilic Formylation of Arenes by Silylium Ion Mediated Activation of Carbon Monoxide

Arene‐stabilized silylium ions react with carbon monoxide rather than carbon monoxide adducts of silylium ions reacting with arenes. This mechanism is supported by quantum‐chemical calculations. Even sterically hindered mesitylene and electronically deactivated chlorobenzene engage in this electrophilic aromatic substitution. The silylium ion mediated formylation corresponds to Gattermann–Koch reactions promoted by strong Brønsted acids. The resulting silylcarboxonium ion of the arenecarbaldehyde was crystallographically characterized, for the first time revealing the molecular structure of this synthetically important intermediate.     

Size-controlled synthesis of colloidal platinum nanoparticles and their activity for the electrocatalytic oxidation of carbon monoxide

Using polyvinylpyrrolidone (PVP) as a stabilizing agent, stable colloidal solutions of platinum nanoparticles of different size distributions have been prepared by reducing H2PtCl6 with hydrogen. The UV-vis adsorption peaks at 258 nm due to the adsorption of Pt(IV) species disappear completely, indicating that the Pt(IV) species has been used up and colloidal Pt has been formed. The electrodes have been prepared from aqueous Pt colloids and glassy carbon (GC). The effect of platinum particle size of Pt/GC catalyst electrode on the electrocatalytic oxidation of carbon monoxide has been investigated. The voltammetry shows that a higher potential is needed for the oxidation of absorbed carbon monoxide with a decrease of the platinum particle size for particle sizes larger than 1 nm. But for particle sizes smaller than 1 nm, the potential remains constant while the activity decreases with decreasing the size. The snowlike, well-dispersed, and highly ordered platinum nanoparticles demonstrate high activity in the oxidation reaction of carbon monoxide. The reason may be due to the geometric structure of platinum nanoparticles.     

Quantum-chemical study of the structure and stability of polymolecular nitrogen,argon, and carbon monoxide clusters

Clusters of atmospheric gases (N₂, CO, Ar) of different composition comprising 11 and 13 molecules have been systematically studied by means of MP2(full)/6-311+G** calculations. The effect of a meduim (a nitrogen or carbon monoxide atmosphere) on the properties of the gas molecule dimers has been revealed, and general trends in the formation of large clusters have been determined.     

Hydrogen bonding between liganded CO and heme-proteins

Perturbations of the CO bond in carbon monoxide bound to iron in different heme-proteins are discussed. Properties evaluated from Hartree-Fock-Slater electronic structure calculations are correlated with experimental observations. The net charge on oxygen (HFS) is related to the Fe(III)/Fe(II) reduction potential (EMF). Consequently, proteins with low EMF, e.g. peroxidases, have more ability to form FeCOH…H. protein hydrogen bonds than, for example, oxidases with higher EMF. This can explain anomalous vibrational frequencies, ν_CO, observed for acidified peroxidases. Calculations reveal that direct interaction between CO and polar groups on the protein can cause peturbations of the CO π-bond order similar to those from EMF shifts. Dioxygen and carbon monoxide are compared in regard to hydrogen bonding to heme-proteins.     

Reactions of cerium atoms and dicerium molecules with CO: formation of cerium carbonyls and photoconversion to CO-activated insertion molecules

Reactions of cerium with carbon monoxide molecules in solid argon have been studied using matrix isolation infrared absorption spectroscopy. The cerium carbonyls CeCO and Ce2CO are produced spontaneously on annealing and they are photochemically rearranged to the CCeO and c-Ce2(mu-C)(mu-O) isomers, where Ce and Ce2 are inserted into the CO triple bond. Theoretical calculations indicate that CeCO is an end-on-bonded carbonyl with a quintet ground state, whereas Ce2CO is a rare dinuclear lanthanide carbonyl complex with CO serving as an asymmetrically bridged, side-on ligand. The CCeO molecule was theoretically characterized to have a linear structure with a singlet ground state. Evidence is also presented for the CeCO- anion and other cerium carbonyls with higher coordination numbers.     

Synthesis and properties of alternating copolymers of carbon monoxide with 5-vinyl-2-norbornene

The alternating cooligomers of carbon monoxide and 5-vinyl-2-norbornene have been first synthesized in the presence of catalysts based on palladium complexes containing N^N and P^P ligands. It has been shown that the insertion of carbon monoxide proceeds for the most part via a C(2)-C(3) bond of the norbornene ring. The degree of involvement of both olefinic bonds of diene in alternating copolymerization is decreased when the reaction is carried out in a protic solvent (methanol). The structure of terminal groups of the copolymers depends on the nature of a bidentate ligand and acid.     

A study of the reaction of oxygen with graphite: model chemistry

A considerable amount of research has been directed towards the mechanism of oxidation of graphite as a model reaction system and because of its industrial importance. A number of recent studies have been concerned with ab initio molecular orbital calculations on graphite including model chemistry and the reactions with molecular oxygen. This study is concerned with oxidation steps involving the attachment of molecular oxygen to the graphene, the formation of carbon monoxide and, in particular, the subsequent oxidation reactions.     

胞嘧啶与一氧化碳复合物的结构与性质

在B3LYP/6-311+G**水平上对胞嘧啶…CO复合物体系进行了理论计算, 发现了6个能量极小的复合物. 其结合方式是CO的C或O原子与胞嘧啶的N—H键形成氢键, 最稳定的复合物的结合能为-8.72 kJ·mol-1. CO的C原子与胞嘧啶的结合具有更强的优势, C原子结合的复合物中CO的键长缩短, 而O结合的复合物中CO键长伸长. 同时, 对复合物的振动分析发现, 在C原子结合的复合物中CO的伸缩频率蓝移, 而O结合的复合物中CO伸缩频率是红移的.     

Matrix isolation spectroscopic and theoretical study of carbon dioxide activation by titanium oxide molecules

The reactions of titanium monoxide and dioxide molecules with carbon dioxide were investigated by matrix isolation infrared spectroscopy. It was found that the titanium monoxide molecule is able to activate carbon dioxide to form the titanium dioxide-carbon monoxide complex upon visible light excitation via a weakly bound TiO(η(1)-OCO) intermediate in solid neon. In contrast, the titanium dioxide molecule reacted with carbon dioxide to form the titanium monoxide-carbonate complex spontaneously on annealing. Theoretical calculations predicted that both activation processes are thermodynamically exothermic and kinetically facile.     

载铜活性炭吸附一氧化碳的密度泛函理论计算

应用密度泛函理论和相对论有效核势方法, 用C₁₆H₁₀, C₁₃H₉, C₁₂H₁₂原子簇模型模拟活性炭表面, 计算得到了CO在载铜活性炭上的吸附位、吸附构型和吸附能. 研究表明: 载铜活性炭吸附CO的过程, 本质上是Cu(I)通过σ-π配键与CO络合, 形成Cu—C键的过程. 载铜活性炭对CO的络合吸附能在50～60 kJ/mol之间, 远大于活性炭对CO的物理吸附能(9.15 kJ/mol), 因而络合吸附更稳定, 选择性也更高. Cu(I)选择吸附在活性炭表面的顶位和桥位, 一个Cu(I)至多可以吸附一个到两个CO分子, 但吸附一个CO比吸附两个CO稳定.     

Oxidation of formic acid and carbon monoxide on gold electrodes studied by surface-enhanced Raman spectroscopy and DFT.

The oxidation of formic acid and carbon monoxide was studied at a gold electrode by a combination of electrochemistry, in situ surface-enhanced Raman spectroscopy (SERS), differential electrochemical mass spectrometry, and first-principles DFT calculations. Comparison of the SERS results and the (field-dependent) DFT calculations strongly suggests that the relevant surface-bonded intermediate during oxidation of formic acid on gold is formate HCOO- ad*. Formate reacts to form carbon dioxide via two pathways: at low potentials, with a nearby water to produce carbon dioxide and a hydronium ion; at higher potentials, with surface-bonded hydroxyl (or oxide) to give carbon dioxide and water. In the former pathway, the rate-determining step is probably related to the reaction of surface-bonded formate with water, as measurements of the reaction order imply a surface almost completely saturated with adsorbate. The potential dependence of the rate of the low-potential pathway is presumably governed by the potential dependence of formate coverage. There is no evidence for CO formation on gold during oxidation of formic acid. The oxidation of carbon monoxide must involve the carboxyhydroxyl intermediate, but SERS measurements do not reveal this intermediate during CO oxidation, most likely because of its low surface coverage, as it is formed after the rate-determining step. Based on inconclusive spectroscopic evidence for the formation of surface-bonded OH at potentials substantially below the surface oxidation region, the question whether surface-bonded carbon monoxide reacts with surface hydroxyl or with water to form carboxyhydroxyl and carbon dioxide remains open. The SERS measurements show the existence of both atop and bridge-bonded CO on gold from two distinguishable low-frequency modes that agree very well with DFT calculations.     

Effect of confinement by porous carbons on the unimolecular decomposition of formaldehyde

As part of an effort to understand the effect of confinement by porous carbons on chemical reactions, we have carried out density functional theory calculations on the unimolecular decomposition of formaldehyde within graphitic carbons. Our results show that the interactions with the carbon walls result in a lowering of the reaction barrier. For larger pores, there is also a shift of the equilibrium towards the formation of carbon monoxide and hydrogen at low temperatures. This trend is reversed for small pore sizes.     

Third-order many-body perturbation theory for the ground state of the carbon monoxide molecule

Many-body perturbation calculations have been performed for the ground state of the carbon monoxide molecule at its equilibrium internuclear separation. The calculations are complete through third order within the algebraic approximation; i.e., the state functions are parameterized by expansion in a finite basis set. All two-, three-, and four-body terms are rigorously determined, and many-body effects are found to be very important. A detailed comparison is made with a previously reported configuration interaction study. Padé approximants to the energy expansion are constructed. The many-body perturbative wave function is used in the Rayleigh quotient to produce upper bounds to the electronic energy.     

The absence of ethylenedione in photochemical biscarbonylation reactions

Photolyses of a number of bridged cyclohexenediones and vinylcyclobutanediones in argon or xenon matrices at 10 K at a variety of wavelengths produced carbon monoxide with no evidence for formation of ethylenedione, the elusive dimer of CO.