Theoretical study on monometallic cyanide cluster fullerenes YCN@C72

The geometries, stabilities, and electronic properties of new endohedral fullerene YCN@C₇₂ have been investigated by the B3LYP and PBE1PBE density functional (DFT) methods. The C_2v(11188)‐C₇₂ cage, which violates the isolated pentagon rule (IPR) with a pair of fused pentagons, is predicted to be the lowest energy isomer for both empty and YCN@C₇₂. The relatively large HOMO‐LUMO gap (B3LYP: 1.48 eV, PBE1PBE: 1.68 eV) for YCN@C_2v(11188)‐C₇₂ reveals this structure kinetic stability. Significantly, the encased YCN cluster adopts a triangular structure inside the C_2v(11188)‐C₇₂ cage, similar to the results reported on YCN@C_s(6)‐C₈₂ and TbCN@C₂(5)‐C₈₂. Furthermore, the vertical ionization potential and electron affinity, UV‐vis‐NIR and IR spectra of YCN@C_2v(11188)‐C₇₂ have been predicted to facilitate future experimental characterization. © 2015 Wiley Periodicals, Inc.     

[GeCN2]分子异构化势能面的理论研究

在CCSD(T)/6-311＋G(2df)//B3LYP/6-311＋G(d)水平下, 研究了四原子分子 [GeCN2]的各个异构体的几何结构、红外振动光谱、相对能量及异构化和解离稳定性, 构建了[GeCN2]势能面. 我们得到了7个[GeCN2]异构体, 包括5个直线型结构GeNCN (1), GeNNC (2), NGeCN (3), NGeNC (4), GeCNN (5)和2个环形结构Ge-cCNN (6)和Ge-cNCN (7). 其中异构体5, 6, 7是我们新找到的构型, 而且GeCNN (5)是整个势能面上稳定性仅次于GeNCN (1)的异构体. 几何和电子结构分析表明, GeCNN (5)具有共轭三键结构: Ge≡C—N≡N:. 由于具有良好的热力学和动力学稳定性, 异构体GeCNN (5)有望在实验中观测到. 我们建议利用过渡金属羰基化合物的络合作用可以进一步稳定GeCNN (5). 本研究为寻找新型含高周期元素的多重键化合物提供了理论线索.     

Theoretical study of the C3Cl radical and its cation

A theoretical study of C₃Cl and C₃Cl⁺ isomers has been carried out. The global minimum for C₃Cl is a cyclic C_2V species (a three-membered ring with an exocyclic chlorine atom). However, a quasi-linear CCCCl structure is predicted to lie only 3-5 kcal mol⁻¹ higher. This quasi-linear structure is floppy, since the linear arrangement lies only 2-3 kcal mol⁻¹ higher in energy. The cyclic and open-chain isomers have dipole moments of 1.986 and 3.363 D, respectively. In C₃Cl⁺ the global minimum is a linear singlet species, the singlet cyclic isomer lying about 19 kcal mol⁻¹ higher. The ionization potentials of cyclic and open-chain C₃Cl are estimated to be 9.17 and 8.21 eV, respectively, suggesting that these species should be easily ionized if present in the interstellar medium.     

Theoretical study of the electronic spectrum of carbonyl cyanide

The ground state properties of carbonyl cyanide and the energies of the electronic transitions are determined by means of the CNDO/2 and CNDO/CI methods respectively. The calculated results are correlated with the observed electronic spectra and assignments are suggested for some previously unassigned transitions. The bonding and delocalization of the electrons of the ground and excited states of the molecule are discussed through an analysis of the molecular orbitals and charge density distributions.

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Zusammenfassung Die Eigenschaften des Grundzustandes von Carbonylcyanide und die Energie von elektronischen Übergängen werden mit Hilfe der Methoden CNDO/2 und CNDO/CI bestimmt. Die berechneten Ergebnisse werden mit dem beobachteten Elektronenspektrum korreliert; für einige bisher nicht klassifizierte Übergänge werden Zuordnungen vorgeschlagen. Die Bindung und Delokalisierung der -Elektronen des Grundzustandes und der angeregten Zustände werden mit Hilfe einer Analyse der MO's und der Ladungsverteilung diskutiert.

     

Theoretical study of the electronic excited states of tetracyanoethylene and its radical anion.

The low-lying electronic states of tetracyanoethylene (TCNE) and its radical anion were studied using multiconfigurational second-order perturbation theory (CASPT2) and extended atomic natural orbital (ANO) basis sets. The results obtained yield a full interpretation of the electronic absorption spectra, explain the spectral changes undergone upon reduction, give support to the occurrence of a bound excited state for the anionic species, and provide valuable information for the rationalization of the experimental data obtained with electron transmission spectroscopy.     

Theoretical study of the CCl3 radical

Employing the STO-3G and 4–31 G basis sets within the unrestricted Hartree-Fock method the equilibrium structure of the CCl₃ radical was calculated. The calculations predict the radical to be non-planar with both basis sets used. Using the UHF optimized geometries the SWX_α calculations have been performed to calculate energy levels, ionization potentials and electron affinities of CCl₃.     

Theoretical study of radical anions of polychlorodibenzo-p-dioxins

The electronic and energetic properties of radical anions of dibenzo-p-dioxins with different number and positions of chlorine atoms in the molecules are investigated by the AM1 method. The stability of radical anions regarding the elimination of chloride anion is studied. There is no obvious difference in dissociation energies of - and -chlorinated dioxins. Isomeric structure of polychlorinated dibenzo-p-dioxins influences electron affinity, -chlorinated dioxins having higher values.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1902–1905, November, 1994.     

Theoretical study of the borane and diborane positive ions

Summary We describe the geometric, electronic and energetic (H _f) properties of B₂H ₆ ⁺ and BH ₃ ⁺ . Comparisons with experimental measurements have also been made with borane, diborane, BH, BH⁺ and BH ₂ ⁺ . All the theoretical calculations have been performed with various basis sets: 6-31G, 6-31G and 6-31⁺G (2d,f). The geometry optimizations are done at the SCF (RHF or UHF), MP2 and MP4 levels.     

HSCCS自由基势能面的理论研究

在CCSD(T)/6-311G(d,f)//MP2/6-311G(d,f) ZPE水平下,计算得到含有8个异构体和11个过渡态的HSCCS自由基体系势能面,讨论了异构体的结构与稳定性及异构体之间的异构化过程.结果表明异构体m1的能量最低,除m1以外,异构体m2和m3的能量也比较低,在MP2水平上,过渡态TS1的能量比异构体m2仅高3.9kJ/mol,而在CCSD(T)水平上,TS1的能量比m2低14.6 kJ/mol,这说明异构体m2可以迅速转化为能量更低的m1.异构体m3的能量比异构体m1高49.99 kJ/mol,可以推断,在合适的实验条件下可以观测到异构体m1.     

Theoretical study of hydrated Be2+ ions

Hydrated Be²⁺ ions [Be(H₂O)_n]²⁺, n = 1−4 and 6, were examined theoretically. The structure of the hydrated ions was determined and the hydration energy estimated with and without electron correlation. The bond between the Be²⁺ ion and the oxygen of water is very strong and has the nature of a dative bond. The non-additivity of the binding energy is so profound that without taking it into account the structure and dynamics of Be²⁺ ions cannot be explained. The hydration number in water is found to be 4. The fifth and sixth water molecules prefer forming the second coordination shell to the Be²⁺ ion. The result is in agreement with X-ray analysis of the aqueous solution, but not with a recent molecular dynamics simulation. In addition, the harmonic vibrational frequencies for the complexes are evaluated and compared with some experiments.     

Anodic oxidation of cyanide and cyanate ions on a platinum electrode

The oxidation processes of cyanide and cyanate ions on a Pt electrode in aqueous and methanol solutions were studied by infrared spectroscopy. In aqueous solution, the cyanide ion was oxidized to cyanate and successively to carbon dioxide. The reaction proceeded on an oxidized platinum surface. In methanol solution, HNCO is the main product during anodization.     

Theoretical study of radical and neutral intermediates of artemisinin decomposition

Four artemisinin reductive decomposition routes A, B1, B2, and B3 with 13 species (QHS, 1/2, 3, 4, 5, 5a, 6, 7, 18, 18a, 19, 20, and 21) were studied at the B3LYP/6-31G** level. Structures of the species were analyzed in terms of geometrical parameters, L?wdin bond orders, partial atomic charges and spin densities, electronic and free energies, and entropy. Searches in the Cambridge Structural Database for high-level quality artemisinin-related structures were also performed. Principal Component and Hierarchical Cluster analyses were performed on selected electronic and structural variables to rationalize relationships between the routes. The A and B1 routes are possibly interconnected. Structural and electronic features of all species show that there are two clusters: A-B1 and B2-B3. The latter cluster is thermodynamically more favorable (DeltaDeltaG is -64 to -88 kcal mol(-1)) than the former (DeltaDeltaG is -58 to -59 kcal mol(-1)), but kinetical preference may be the opposite. Along the artemisinin decomposition routes, especially B2 and B3, larger structural changes including formation of branched structures and CO2 release are related to increased exothermicity of the conversions, weakened attractive oxygen-oxygen interactions, and increased entropy of the formed species. The intermediate 4 definitely belongs to some minor artemisinin decomposition route.     

Theoretical study on the reaction mechanism of CN radical with ketene

The bimolecular single collision reaction potential energy surface of CN radical with ketene (CH2CO) was investigated by means of B3LYP and QCISD(T) methods. The calculated results indicate that there are three possible channels in the reaction. The first is an attack reaction by the carbon atom of CN at the carbon atom of the methylene of CH2CO to form the intermediate NCCH2CO followed by a rupture reaction of the C-C bond combined with -CO group to the products CH2CN CO. The second is a direct addition reaction between CN and CH2CO to form the intermediate CH2C(O)CN followed by its isomerization into NCCH2CO via a CN-shift reaction, and subsequently, NCCH2CO dissociates into CH2CN CO through a CO-loss reaction. The last is a direct hydrogen abstraction reaction of CH2CO by CN radical. Because of the existence of a 15.44 kJ/mol reaction barrier and higher energy of reaction products, the path can be ruled out as an important channel in the reaction kinetics. The present theoretical computation results, which give an available suggestion on the reaction mechanism, are in good agreement with previous experimental studies.     

Theoretical study on the reaction mechanism of vinyl radical with formaldehyde

A detailed computational study is performed on the radical-molecule reaction between the vinyl radical (C2H3) and formaldehyde (H2CO), for which only the direct hydrogen abstraction channel has been considered by previous and very recent theoretical studies. At the Gaussian-3//B3LYP/6-31G(d) and CBS-QB3 levels, the direct H-abstraction forming C2H4 + HCO has barriers of 3.9 and 4.7 kcal/mol, respectively. The addition barrier to form H2CCHCH2O has barriers of 2.8 and 2.3 kcal/mol, respectively. Subsequently, there are two highly competitive dissociation pathways for H2CCHCH2O: One is the formation of the direct H-extrusion product H2CCHCHO + H, and the other is the formation of C2H4 + HCO via the intermediate H2CCH2CHO. Surely, the released energy is large enough to drive the secondary dissociation of HCO to H + CO. Because the involved transition states and intermediates of the H2CCHCH2O evolution all lie energetically lower than the entrance addition transition state, the addition-elimination is more competitive than the direct H-transfer for the C2H3 + H2CO reaction, in contrast to previous expectation. The present results can be useful for future experimental investigation on the title reaction.     

Theoretical study on the gas-phase reaction of acetaldehyde with methoxy radical

Structural Chemistry - The reaction of acetaldehyde with methoxy radical has been investigated theoretically by means of quantum chemistry methods at the BMC-QCISD//B3LYP/6-311+G(d,p) level. The...     

Theoretical mechanistic study on the reaction of CN radical with HNCN

The mechanism for the reaction of the cyanogen radical (CN) with the cyanomidyl radical (HNCN) has been investigated theoretically. The electronic structure information of the singlet and triplet potential energy surfaces (PESs) is obtained at the B3LYP/6-311+G(3df,2p) level, and the single-point energies are refined at the CCSD(T)/6-311+G(3df,2p) level as well as by multilevel MCG3-MPWB method. The calculations show that the C atom of CN additions to middle- and end-N atoms of HNCN are two barrierless association processes leading to the energy-rich intermediates IM1 HN(CN)CN and IM2 HNCNCN, respectively, on the singlet PES. The higher barriers of the subsequent isomerization and dissociation channels from IM1 and IM2 indicate that these two intermediates, which have considerably thermodynamic and kinetic stability, are the dominant product at high pressure. While at low pressure, the most favorable product is P(2) H + NCNCN, which will be formed from both IM1 and IM2 via direct dissociation processes by the H-N bond rupture, and the secondary feasible product is P(4) HCN + (1) NCN, while P(5) HCCN + N(2) and P(6) HCNC + N(2) are the least competitive products. On the triplet PES, P(14) NCNC + HN may be a comparable competitive product at high temperature. In addition, the comparison between the mechanisms of the CN + HNCN and OH + HNCN reactions is made. The present results will enrich our understanding of the chemistry of the HNCN radical in combustion processes and interstellar space.     

Theoretical study on reaction mechanism of isocyanate radical NCO with ethene

The NCO + C₂H₄ reaction is simple and prototype for reaction of the NCO radical with unsaturated hydrocarbons, and it is considered to be important in fuel‐rich combustion. In this article, we for the first time perform detailed theoretical investigations for its reaction mechanism based on Gaussian‐3//B3LYP scheme covering various entrance and decomposition channels. The most favorable channel is firstly the NCO and C₂H₄ approach each other, forming a weakly‐bound complex L1 OCN···C₂H₄, followed by the formation of isomer L2 OCNCH₂CH₂ via a small barrier of 1.3 kcal/mol. Transition states of any decomposable or isomeric channels for L2 in energy are much higher than reactants, which indicate that adduct L2 has stabilization effect in this NCO + C₂H₄ reaction. The direct H‐abstraction channel leading to P1 HNCO + C₂H₃, might have an important contribution to the eventual products in high temperature. These results can well explain available kinetic experiment. Moreover, reaction mechanism for the title reaction is significantly different from the NCO + C₂H₂ reaction which proceeds on most favorably to generate the products HCN + HCCO and OCCHCN + H via a four‐membered ring intermediate. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Viscosity B-coefficients of the aqueous cyanide and azide ions

A number of factors have led us to re-examine the literature assignments of the viscosity B-coefficients of the individual cyanide and azide ions in aqueous solutions at 25°C. The revised values, obtained from mutually confirmatory correlations, are: B(CN^–)=–0.020±0.007 and B(N ₃ ^– )=–0.014#±#0.006>dm³-mol^–1