Calculation of molecular integrals for systems confined by hard spherical walls: Use of the single‐center expansion of floating spherical gaussians

Assuming a gaussian basis set representation of atomic and molecular wave functions, the single‐center expansion of off‐centered spherical gaussian orbitals is exploited to calculate the one and two‐electron integrals for multielectronic atoms and molecules confined within hard spherical walls. As a validating test, the ground‐state energy of a helium atom positioned off‐center in a spherical box is calculated by applying the simplest form of the floating spherical gaussian orbital (FSGO) scheme, i.e., the use of a primitive basis set consisting of a single FSGO per electron pair. Comparison with corresponding recent accurate calculations gives supporting evidence of the adequacy of the method for its application to more elaborate gaussian‐type basis set representations for confined atoms and molecules. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 271–278, 2001     

The electronic structure of polymers by the FSGO (Floating Spherical Gaussian Orbital) method

Non-empirical band-structure calculations have been performed on polyethylene using two basis sets introduced by Christoffersen. Both basis sets had to be optimised with respect to the carbon-carbon framework bond in order to yield solutions within the nearest-neighbour approximations. The valence bands of polyethylene are well reproduced by both basis sets whilst the conduction bands are only in fair agreement with those produced by conventional gaussian calculations. The use of the unsplit basis set was considered unsatisfactory for the representation of the core bands. The effect of increasing the number of interacting unit cells on the energy terms is discussed. Some of the energy terms converge when five unit cells are used and almost all of the terms reach a constant value when nine unit cells are employed.     

Analytic expression of the second derivatives of electronic energy for full configuration interaction wave functions

Summary A new analytic second derivative expression of the electronic energy is derived for full configuration interaction (CI) wave functions. This formula is shown to be free from the derivative terms of both CI and MO coefficients. The second-order relationships between CI and MO coefficients for full CI wave functions are also presented.     

Analytic first and second derivatives of the energy in the fragment molecular orbital method combined with molecular mechanics

Analytic first and second derivatives of the energy are developed for the fragment molecular orbital method interfaced with molecular mechanics in the electrostatic embedding scheme at the level of Hartree-Fock and density functional theory. The importance of the orbital response terms is demonstrated. The role of electrostatic embedding upon molecular vibrations is analyzed, comparing force field and quantum mechanical treatments for an ionic liquid and a solvated protein. The method is applied for 100 protein conformations sampled in molecular dynamics (MD) to take into account the complexity of a flexible protein structure in solution, and a good agreement with experimental data is obtained: Frequencies from an experimental infrared (IR) spectrum are reproduced within 17 cm⁻¹ .     

Analytical TDHF second derivatives of dynamic electronic polarizability with respect to nuclear coordinates. Application to the dynamic ZPVA correction

Analytical calculation of second derivatives of the dynamic electronic polarizability with respect to vibrational normal coordinates has been implemented at the TDHF level of approximation. Important simplifications are obtained by using the 2n+1 rule and interchange relations. In application to small molecules the first‐order ZPVA correction is found to have greater frequency dispersion than the electronic polarizability, but the former remains small in comparison. For the linear polyenes, C_2nH_2n+2 (n=1–3), the percentage ZPVA correction decreases with chain length for all ?ω<0.10 a.u. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1920–1932, 2001     

复热食用植物油结构变化的红外吸收光谱分析

利用衰减全反射(ATR)傅立叶红外光谱(FTIRS)法对市售优质品牌的8种植物油(转基因豆油、非转基因豆油、葵花籽油、花生油、玉米油、红花籽油、调和油、橄榄油)未加热及反复高温加热后的红外二阶导数光谱进行比较,发现复热食用油在反复高温加热下会使不饱和脂肪酸亚油酸、亚麻酸的含量降低,饱和脂肪酸棕榈酸和硬脂酸的含量增加;顺式脂肪酸的含量下降,反式脂肪酸的含量明显增加。确定以二阶导数光谱中3 009、988、966 cm-13处特征吸收峰的峰高判定是否为反复加热用油。此方法样品用量少、分析速度快,可从整体上了解油品的质量及成分,并可作为市场复热食用油的快速筛查方法,也可为地沟油检测方法的建立提供理论依据。     

A dataset of highly accurate homolytic NBr bond dissociation energies obtained by Means of W2 theory

Homolytic N? Br bond dissociation constitutes the initial step of numerous reactions involving N‐brominated species. However, little is known about the strength of N? Br bonds toward homolytic cleavage. We herein report accurate bond dissociation energies (BDEs) for a set of 18 molecules using the high‐level W2 thermochemical protocol. The BDEs (at 298 K) of the species in this set range from 162.2 kJ mol^?1 (N‐bromopyrrole) to 260.6 kJ mol^?1 ((CHO)₂NBr). In order to compute BDEs of larger systems, for which W2 theory is not applicable, we have benchmarked a wide range of more economical theoretical procedures. Of these, G3‐B3 offers the best performance (root‐mean‐square deviations = 2.9 kJ mol^?1), and using this method, we have computed N? Br BDEs for four widely used N‐brominated compounds. These include (BDEs are given in parentheses): N‐bromosuccinimide (281.6), N‐bromoglutarimide (263.2), N‐bromophthalimide (274.7), and 1,3‐dibromo‐5,5‐dimethylhydantoin (218.2 and 264.8 kJ mol^?1). © 2015 Wiley Periodicals, Inc.     

Selective formation of either Tröger’s base or spiro Tröger’s base derivatives from [2-aminoporphyrinato(2-)]nickel by choice of reaction conditions

The article reports on the unique manipulation of the acid-catalyzed reaction of [2-aminoporphyrinato(2-)]nickel with formaldehyde to form selectively either the symmetric Tröger’s base or the asymmetric spiro Tröger’s base bis(metalloporphyrin) derivative. The reaction is driven by the choice of acid catalyst, formaldehyde source, and particularly, solvent, to give a mixture of both derivatives in preparative yields of about 90%, or to give selectively one of the derivatives in a yield of about 60%.     

Cloud point extraction of iron(III) and vanadium(V) using 8-quinolinol derivatives and Triton X-100 and determination of 10(-7)moldm(-3) level iron(III) in riverine water reference by a graphite furnace atomic absorption spectroscopy

The cloud point extraction behavior of iron(III) and vanadium(V) using 8-quinolinol derivatives (HA) such as 8-quinolinol (HQ), 2-methyl-8-quinolinol (HMQ), 5-butyloxymethyl-8-quinolinol (HO₄Q), 5-hexyloxymethyl-8-quinolinol (HO₆Q), and 2-methyl-5-octyloxymethyl-8-quinolinol (HMO₈Q) and Triton X-100 solution was investigated. Iron(III) was extracted with HA and 4% (v/v) Triton X-100 in the pH range of 1.70-5.44. Above pH 4.0, more than 95% of iron(III) was extracted with HQ, HMQ, and HMO₈Q. Vanadium(V) was also extracted with HA and 4% (v/v) Triton X-100 in the pH range of 2.07-5.00, and the extractability increased in the following order of HMQ < HQ < HO₄Q < HO₆Q. The cloud point extraction was applied to the determination of iron(III) in the riverine water reference by a graphite furnace atomic absorption spectroscopy. When 1.25 × 10⁻³ M HMQ and 1% (v/v) Triton X-100 were used, the found values showed a good agreement with the certified ones within the 2% of the R.S.D. Moreover, the effect of an alkyl group on the solubility of 5-alkyloxymethyl-8-quinolinol and 2-methyl-5-alkyloxymethyl-8-quinolinol in 4% (v/v) Triton X-100 at 25 °C was also investigated.     

Ab initio molecular orbital study of potential energy surface for the H2NO(B1)→NO(Π)+H2 reaction

The mechanism of the H₂NO(²B₁)→NO(²Π)+H₂ reaction has been examined using ab initio molecular orbital methods. Ground-state and first-excited-state potential surfaces were plotted at the FOCI/cc-pVTZ level of theory as functions of two appropriate internal degrees of freedom. A conical intersection was found on the C_s pathway that is symmetric with respect to the plane perpendicular to the molecular plane of C_2v H₂NO(²B₁). It is therefore considered that trajectories that start from H₂NO(²B₁) towards the product region detour around the conical intersection, pass through the neighborhood of the transition state that is located at the saddle point on the C_s pathway, and finally reach the products, NO(²Π)+H₂. Thus we can explain the mechanism of the H₂NO(²B₁)→NO(²Π)+H₂ reaction, which has remained unclear to date.     

Binding of cationic and neutral phenanthridine intercalators to a DNA oligomer is controlled by dispersion energy: quantum chemical calculations and molecular mechanics simulations

Correlated ab initio as well as semiempirical quantum chemical calculations and molecular dynamics simulations were used to study the intercalation of cationic ethidium, cationic 5-ethyl-6-phenylphenanthridinium and uncharged 3,8-diamino-6-phenylphenanthridine to DNA. The stabilization energy of the cationic intercalators is considerably larger than that of the uncharged one. The dominant energy contribution with all intercalators is represented by dispersion energy. In the case of the cationic intercalators, the electrostatic and charge-transfer terms are also important. The DeltaG of ethidium intercalation to DNA was estimated at -4.5 kcal mol(-1) and this value agrees well with the experimental result. Of six contributions to the final free energy, the interaction energy value is crucial. The intercalation process is governed by the non-covalent stacking (including charge-transfer) interaction while the hydrogen bonding between the ethidium amino groups and the DNA backbone is less important. This is confirmed by the evaluation of the interaction energy as well as by the calculation of the free energy change. The intercalation affects the macroscopic properties of DNA in terms of its flexibility. This explains the easier entry of another intercalator molecule in the vicinity of an existing intercalation site.     

Gibbs energy of activation for thermal isomerization of (1Z)‐acetaldehyde hydrazone and (1Z)‐acetaldehyde N,N‐dimethylhydrazone by Gaussian‐4 theory and CCSD(T)/CBS computations

In this article, we examined the Gibbs energy of activation for the Z/E thermal isomerization reaction of (1Z)‐acetaldehyde hydrazone and (1Z)‐acetaldehyde N,N‐dimethylhydrazone, at 298.15 K in the solvent of cyclohexane. We carried out computations employing both the Gaussian‐4 (G4) theory and the coupled cluster method using both single and double substitutions and triple excitations noniteratively, CCSD(T). The CCSD(T) energy is extrapolated to the complete basis set (CBS). We compared the calculated results to the available experimental observation. It appeared that both G4 and CCSD(T)/CBS computations overestimated the experimental value by as much as about 6 and 12 kcal/mol in the present two cases. We discussed possible sources of error and proposed the experimental kinetic data could be questionable. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009