Theoretical Investigation of the Reactivity of Copper Atoms with OCS: Comparison with CS2 and CO2

Thermodynamic and Kinetic Aspects of the Reactions of Titanium(I) ion with the Sulfurtransfer Reagent SCO via the C22O Bond Activation Pathway

Theoretical studies on the thermodynamic and kinetic aspects of the reactions of Ti+ ion with the sulfur-transfer reagent SCO via the C22O bond activation pathway have been carried out over the temperature range 200 — 1200K using the DFT=B3LYP method, general statistical thermodynamics and Eyring transition state theory with the Wigner correction. The relevant reactions comprise: reaction 1 [Formula: see text], and reaction 2 [Formula: see text] in which the spin multiplicity changes from the quartet state to the doublet state in the crossing region. It is concluded that the order of the equilibrium constants (K) and the reaction rate constants (k) are consistent with that of their corresponding exoergic energies DE and reaction barriers, respectively, and their differences at low temperature are larger than those at high temperature. Step 2 of reaction 1 is both thermodynamically and kinetically favoured over the entire temperature range. Moreover, both reactions 1 and 2 are exothermic and proceed spontaneously in which their entropy increases, and the magnitudes of their thermodynamic constants all decrease with rising temperature. The calculated DH8, DG8, and DS8 values of the two reactions are relatively similar. However, because reactants 4Ti+ and SCO have a lower energy than that of reactants 2Ti+ and SCO, it is reaction 2, in which the quartet state is changed to the doublet state through intersystem crossing, which should be seen as dominant.

Correlated Molecular Orbital Theory Study of the Al + CO2 Reaction

Density functional theory (DFT) and correlated molecular orbital electronic structure calculations were used to study the Al + CO₂ → AlO + CO reaction on the electronic ground-state potential-energy surface (PES). Geometries were optimized using DFT (M11/jun-cc-pV(Q+d)Z) and more accurate energies were obtained using the composite Weizmann-1 theory with Brueckner doubles (W1BD). The results comprise the most complete, most systematic characterization of the Al + CO₂ reaction surface to date and are based on consistent application of high-level methods for all stationary points identified. The pathways from Al + CO₂ to AlO + CO on the electronic ground-state PES all involve formation of one or more stable AlCO₂ complexes denoted η-AlCO₂, trans-AlCO₂, and C_2v-AlCO₂, among which η-AlCO₂ and C_2v-AlCO₂ are the least and most stable, respectively. We report a new minimum-energy pathway for the overall reaction, namely formation of η-AlCO₂ from reactants and dissociation of that same complex to products via a bond-insertion reaction that passes through a fourth (weakly metastable) AlCO₂ complex denoted cis-OAlCO. Natural Bond Orbital analysis was applied to study trends in charge distribution and the degree of charge transfer in key structures along the minimum-energy pathway. The process of aluminum insertion into CO₂ is discussed in the context of analogous processes for boron and first-row transition metals.

Dissociation of CO2 on rhodium nanoclusters (Rh13) in various structures supported on unzipped graphene oxide – a DFT study

Carbon dioxide could readily dissociate to form CO on an unzipped graphene oxide supported icosahedral structure of Rh₁₃ (Rh₁₃-I_h/UGO).

Infrared spectra and structures of the neutral and charged CrCO2 and Cr(CO2)2 isomers in solid neon

The reactions from codeposition of laser-ablated chromium atoms with carbon dioxide in excess neon are studied by infrared absorption spectroscopy. The species formed are identified by the effects of isotopic substitution on their infrared spectra. Density functional calculations are performed to support the spectral assignments and to interpret the geometric and electronic structures of the experimentally observed species. Besides the previously reported insertion products OCrCO and O2Cr(CO)2, the one-to-one Cr(CO2) complex and the one-to-two Cr(CO2)2 complex as well as the CrOCrCO and OCCrCO3 complexes are also formed. The Cr(CO2) complex is characterized to be side-on η(2)-C,O-coordinated. The Cr(CO2)2 complex is identified to involve a side-on η(2)-C,O-coordinated CO2 and an end-on η(1)-O-coordinated CO2. OCCrCO3 is a carbonate carbonyl complex predicted to have a planar structure with a η(2)-O,O-coordinated carbonate ligand. The CrOCrCO complex is predicted to be linear with a high-spin ground state. Besides the neutral molecules, charged species are also produced. The Cr(CO2)(+) and Cr(CO2)2(+) cation complexes are characterized to have linear end-on η(1)-O-coordinated structures with blue-shifted antisymmetric CO2 stretching vibrational frequencies. The OCrCO(-) anion is bent with the Cr-O and CO stretching frequencies red-shifted from those of OCrCO neutral molecule.

Density functional studies of the adsorption and dissociation of CO2 molecule on Fe(111) surface

Spin-polarized density functional theory calculation was carried out to characterize the adsorption and dissociation of CO(2) molecule on the Fe(111) surface. It was shown that the barriers for the stepwise CO(2) dissociation reaction, CO(2(g)) --> C(a) + 2O(a), are 21.73 kcal/mol (for OC-O bond activation) and 23.87 kcal/mol (for C-O bond activation), and the entire process is 35.73 kcal/mol exothermic. The rate constants for the dissociative adsorption of CO(2) have been predicted with variational RRKM theory, and the predicted rate constants, k(CO(2)) (in units of cm(3) molecule(-1) s(-1)), can be represented by the equations 2.12 x 10(-8)T(-0.842) exp(-0.258 kcal mol(-1)/RT) at T = 100-1000 K. To gain insights into high catalytic activity of the Fe(111) surface, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis.

Thermodynamic and kinetic properties of scandium (I) ion reacting with SCO in gas phase

Theoretical studies on the thermodynamic and kinetic properties of the reactions of scandium (I) ion with the sulfur-transfer reagent SCO via the C-O bond activation pathway have been carried out over the temperature range of 200-1200 K using the DFT/B3LYP method, general statistical thermodynamics, and Eyring transition state theory with Wigner correction. The relevant reactions include reaction 1 1Sc+ + SCO → 1IM1 → 1TS1 → 1IM2 (Step 1) → 1TS2 → 1IM3 → 1ScO+ + 1CS (Step 2), and reaction 2 3Sc+ + SCO → 3IM1 → CP → 1IM2 → 1TS2 → 1IM3 → 1ScO+ +1CS in which the spin multiplicity changes from the triplet state to the singlet state in the crossing region. It was concluded that the order of the equilibrium constants (K) and the reaction rate constants (k) are consistent with that of their corresponding exoergic energies, ΔE, and reaction barriers, respectively. Step 2 of reaction 1 is both thermodynamically and kinetically favored over the whole temperature range. Moreover, both Reaction 1 and reaction 2 are exothermic and spontaneous processes in which their entropy increases, and the magnitudes of their thermodynamic values all decrease with increasing temperature.