Quantenmechanische Untersuchungen von Atom-, Bindungs-und Molekülpolarisierbarkeiten,spektroskopische Untersuchungen der Schwingungskonstanten und statistische Thermodynamik: Perchloryl- und Perbromylfluorid

Zusammenfassung Perchloryl- und Perbromylfluorid haben dreizählige Symmetrie. Ihre IR- und Ramanspektren sowie die Ergebnisse von Untersuchungen der Molekülstruktur und andere spektroskopische Untersuchungen werden kurz besprochen. Aus den verschiedenen quantenmechanischen Modellen wird das Deltafunktion-Potentialmodell, das aus der Variationsmethode und den Deltafunktions-Elektronenwellenfunktionen beruht, ausgewählt, um die Atompolarisierbarkeiten, die zur Bindungsachse parallelen und auf sie senkrecht stehenden Beiträge der bindenden und der nichtbindenden Elektronen zur Polarisierbarkeit und die mittlere molekulare Polarisierbarkeit der beiden Moleküle zu berechnen. Mit Hilfe gruppentheoretischer Überlegungen werden die Konstanten der potentiellen Energie berechnet. Hierzu wird ein Bindungskraftfeld mit sechs Konstanten angenommen. Für das erhaltene Kraftfeld werden für 298 und 500 °K die Wurzeln der mittleren Amplitudenquadrate der gebundenen und der nichtgebundenen Atompaare berechnet. Unter der Annahme des Modells eines starren Rotators und harmonischen Oszillators werden für den Temperaturbereich 200 bis 2000 °K die Enthalpiefunktion, die freie Energiefunktion, die Entropie und die Molwärme der beiden Moleküle berechnet. Die Ergebnisse werden hinsichtlich der Natur der beiden in den Molekülen vorliegenden charakteristischen Bindungen besprochen.

---

Quantum mechanical studies of atomic, bond, and molecular polarizabilities, spectroscopic studies of vibrational constants, and statistical thermodynamics: Perchloryl and perbromyl fluorides

Perchloryl and perbromyl fluorides possessing a three-fold symmetry have been briefly analyzed for the infrared asorption and Raman spectra, molecular structural studies, and other spectroscopic investigations. Among the various quantum mechanical models, the delta-function potential model based on the variational method and delta-function electronic wave functions has been employed here to evaluate the atomic polarizabilities, the contributions by the bonding and nonbonding electrons to the bond parallel component of the polarizability, the bond perpendicular component of the polarizability, and the mean molecular polarizability for these two molecules. On the basis of group theoretical considerations, the potential energy constants have been evaluated by employing a six-constant valence force field. The root-mean-square amplitudes for both bonded an nonbonded atom pairs have been computed at the temperatures 298 °K and 500 °K from the developed force field. On the basis of a rigid rotator and harmonic oscillator model, enthalpy function, free energy function, entropy, and heat capacity have also been computed for the temperatures from 200 °K to 2000 °K for these two molecules. The results have been discussed in relation to the nature of the two characteristic bonds involved in both the molecular systems.

---

---

Mit 7 Abbildungen     

Computed vibrational frequencies of actinide oxides AnO(0/+/2+) and AnO2(0/+/2+) (An = Th, Pa, U, Np, Pu, Am, Cm)

The vibrational frequencies of the actinide oxides AnO and AnO(2) (An = Th, Pa, U, Np, Pu, Am, Cm) and of their mono- and dications have been calculated using advanced quantum chemical techniques. The stretching fundamental frequencies of the monoxides have been determined by fitting the potential function to single-point energies obtained by relativistic CASPT2 calculations along the stretching coordinate and on this basis solving numerically the ro-vibrational Schro?dinger equation. To obtain reliable fundamental frequencies of the dioxides, we developed an empirical approach. In this approach the harmonic vibrational frequencies of the AnO(2)(0/+/2+) species were calculated using eight different exchange-correlation DFT functionals. On the basis of the good correlation found between the vibrational frequencies and computed bond distances, the final frequency values were derived for the CASPT2 reference bond distances from linear regression equations fitted to the DFT data of each species. As a test, the approach provided excellent agreement with accurate experimental data of ThO, ThO(+), UO, and UO(+). The joint analysis of literature experimental and our computed data facilitated the prediction of reliable gas-phase molecular properties for some oxides. They include the stretching frequencies of PuO, ThO(2), UO(2), and UO(2)(+) and the bond distance of PuO (1.818 ?, being likely within 0.002 ? of the real value). Also the derived equilibrium bond distances of ThO(2), UO(2), and UO(2)(+) (1.896, 1.790, and 1.758 ?, respectively) should approximate closely the (yet unknown) experimental values. On the basis of the present results, we suggest that the ground electronic state of PuO(2) in Ar and Kr matrices is probably different from that in the gaseous phase, similarly to UO(2) observed previously.     

Chemical bonding in the crystal structure of 1-hydrosilatrane

A study has been made of the crystal and molecular structure of 1-hydrosilatrane HSi(OCH_2CH₂)₃N. The quantum chemical calculations of its crystal structure have been carried out. According to an estimate of the energy, the coordination bond N→Si is by 5 kcal mol^?1 stronger than that in the crystal of 1-methylsilatrane. The charge values calculated within the framework of the topological analysis of the electron density demonstrate that the electron density of the coordination bond N→Si is primarily transferred to the region of the equatorial bonds Si—O and, to a lesser extent, to the bond Si—H. On going from the isolated molecule of 1-hydrosilatrane to its crystal, the interatomic distance N—Si decreases, mainly owing to the weak intermolecular interaction C—H...O.     

The rotational spectrum,nuclear spin—spin coupling,nuclear quadrupole coupling,and molecular structure of KrHF

Rotational spectra have been assigned for the ⁸²Kr, ⁸³Kr, ⁸⁴Kr, and ⁸⁶Kr isotopic species of the KrHF and KrDF van der Waals molecules by using pulsed microwave Fourier transform spectroscopy in a Fabry—Perot cavity with a pulsed supersonic nozzle molecular source. The rotational, centrifugal distortion, nuclear spin—spin, and nuclear quadrupole coupling constants are used to determine the structure and obtain intramolecular potential binding information. The ⁸³Kr nuclear quadrupole coupling constants are 10.28 ± 0.08 MHz and 13.83 ± 0.13 MHz for KrHF and KrDF respectively. The electric field gradient at the krypton nucleus is calculated from the coupling constant and the known nuclear quadrupole moment and explained by Sternheimer shielding and formation of the van der Waals bond. There is a negligible charge transfer in the KrHF bond.     

Konstanten der potentiellen Energie,mittlere Schwingungs-amplituden,Bastiansen—Morino-Schrumpfeffekt und thermodynamische Funktionen einiger isotoper Arten des Chlorcyans

Zusammenfassung Mit Hilfe der gruppentheoretischen Methode werden aus den Grundschwingungsfrequenzen isotoper Arten des Chlorcyans, das eine lineare asymmetrische Struktur der Symmetriepunktgruppe C _v besitzt, vier Bindungskraftkonstanten ermittelt. Aus den Symmetriekoordinaten werden von den gebundenen und nichtgebundenen Atompaaren die mittleren Amplitudenquadrate die verallgemeinerten mittleren Amplitudenquadrate (mittlere Parallelamplitudenquadrate, mittlere Senkrechtamplitudenquadrate und mitlere gemischte Produkte) und die mittleren Schwingungsamplituden für die Temperaturen 298°K, 500°K und 1000°K berechnet. Außer diesen Molekülkonstanten werden für alle vier isotopen Arten des Moleküls die molaren thermodynamischen Funktionen für den Temperaturbereich von 200°K bis 2000°K berechnet. Dieser Rechnung wird das Modell eines harmonischen Oszillators und starren Rotators zugrunde gelegt. Die Natur der beiden charakteristischen Bindungen wird an Hand der erhaltenen Ergebnisse kurz besprochen.

---

Potential energy constants, mean amplitudes of vibration, bastiansen—Morino shrinkage effect and thermodynamic functions in some isotopic species of cyanogen chloride

On the basis of the group theoretical method four valence force constants have been evaluated by employing the fundamental frequencies of isotopic species of the cyanogen chloride molecule possessing a linear asymmetrical structure with the symmetry point group C_v. Mean-square amplitude quantities, generalized mean-square amplitude quantities (mean-square parallel amplitudes, mean-square perpendicular amplitudes and mean cross products), and mean amplitudes of vibration for the bonded and nonbonded atom pairs have been computed at the temperatures 298°K, 500°K, and 1000°K by employing the symmetry coordinates. In addition to these molecular constants, the molar thermodynamic functions for all the four isotopic species of the molecule have also been calculated for the temperature range 200–2000°K on the assumption of a rigid rotator, harmonic oscillator model. A brief discussion of the results is given with respect to the nature of the two characteristic bonds.

---

---

Diese Arbeit wurde vom U.S. Army Research Office-Durham unter dem Zeichen Grant DA-ARO-D-31-124-G 864 unterstützt.     

The Distance between Minima of Electron Density and Electrostatic Potential as a Measure of Halogen Bond Strength

In this study, we present results of a detailed topological analysis of electron density (ED) of 145 halogen-bonded complexes formed by various fluorine-, chlorine-, bromine-, and iodine-containing compounds with trimethylphosphine oxide, Me₃PO. To characterize the halogen bond (XB) strength, we used the complexation enthalpy, the interatomic distance between oxygen and halogen, as well as the typical set of electron density properties at the bond critical points calculated at B3LYP/jorge-ATZP level of theory. We show for the first time that it is possible to predict the XB strength based on the distance between the minima of ED and molecular electrostatic potential (ESP) along the XB path. The gap between ED and ESP minima exponentially depends on local electronic kinetic energy density at the bond critical point and tends to be a common limiting value for the strongest halogen bond.     

Effect of the molecular structure on the strength of the C-NO<Subscript>2</Subscript> bond in a series of monofunctional nitrobenzene derivatives

Geometric parameters and formation enthalpy and the enthalpy of the radicals formed during the homolytic breakage of C-NO₂ bond in 37 aromatic nitro compounds were calculated using different bases of the hybrid density functional method B3LYP, as well as the composite CBS-QB3 methods. On the basis of thermochemical data, were calculated the C-NO₂ bond dissociation energy and the activation energy of the radical gas-phase decomposition. Donor substituents were shown to cause an increase in the C-NO₂ bond dissociation energy, while the acceptors decrease it. The values of activation energies of gas-phase decomposition of aromatic nitro compounds calculated basing on the C-NO₂ bond dissociation energy are in good agreement with experiment.     

氯化钕异丙醇配合物的电子结构与络合活化的研究

本文用INDO方法计算了氯化钕异丙醇配合物的电子结构。计算结果指出, 配位后, 与Nd-Cl键对应的分子轨道能量升高, Nd-Cl键级降低, Nd的正电荷降低, Cl的负电荷增多。从而表明。由于配位发生轨道重迭, 使得异丙醇氧的孤对电子移向钕离子的空价轨道。钕离子上的电子云密度增高加强了对Nd—Cl键的价电子的推斥作用, 使Nd-Cl间的价电子密度减小, 导致Nd-Cl键的削弱, 降低了键的能量, 有效地活化了Nd-Cl键,有利于生成活性物种的烷基化反应的进行。同时表明, 对Nd-Cl的络合催化有某种选择性。     

Procedures leading to a variety of orthonormal Jacobi-type coordinates of relevance to large-amplitude vibration and scattering problems

Algorithms are developed to produce transformation matrices to convert from scalar bond distance—angle coordinates to scalar coordinates corresponding to a variety of Jacobi-type orthonormal coordinates defined by the usual Gram—Schmidt process, or by alternates taking into account symmetries inherent in the molecular hamiltonian. The transformations have been developed with computer implementation in mind.     

Theoretical study of the molecular structure and normal coordinate analysis of hydrogen cyanide addition compound with boron trifluoride, HCN-BF(3)

An extensive HF, MP2, B3LYP and CCSD study of the molecular structure and normal vibrations have been performed for the HCN-BF(3) molecule. Calculations with a wide range of basis sets were classified into two groups based on the optimized N-B bond distance. The results for Group A are compared with the experimental structure of the solid phase molecules. The N-B lengths of Group A are approximately linear related to the N-B-F valence angles and also to the N-B stretching frequencies. HF/DZV calculation was used to represent the solid phase model. The N-B lengths of Group B are close to those of the gas phase molecule and both N-B-F angles and N-B sensitive frequencies have roughly the same values. Differences in the chemical bond between gaseous and solid phase HCN-BF(3) are discussed based on the calculated force constants, vibrational frequencies and potential energy distributions. Vibration mode analysis indicates that the nu(4) mode in the 600-700 cm(-1) region can be assigned to the BF(3) symmetric deformation, which shifts upon (10)B/(11)B isotopic substitution. The nu(5) mode which is insensitive to isotope substitution and changes band position with the N-B distance is assigned to the N-B bond stretching vibration.     

LCAO–MO studies on hydrogen bonding: The interaction between carbonyl and hydroxyl groups

Potential curves that show the energy dependence of hydrogen bonds between carbonyl and hydroxyl groups on the O? H bond length, on the distance between the molecules, and on the angle between the functional groups have been calculated with the CNDO /2 method. The results are presented for a small model system–formaldehyde/water—and for the dimer of formic acid. Good agreement is obtained with the available experimental data. The influence of the molecular geometry on the calculated results is discussed.     

煤显微组分分子结构模型的量子化学研究

采用分子力学和半经验量子化学方法，研究了神木煤显微组分的分子结构模型，比较了镜质组和惰质组分子模型的能量构成、不同类型键的键长和键裂解能。研究结果表明，扭转能和范德华能是分子中的主要作用力，取代基对体系能量有明显影响，烷基取代基使体系能量增加，而苯基取代基使体系能量降低；脂肪C—C键长比芳香C—C键长长，说明脂肪C—C在受热过程中比芳香C—C更容易断裂分解。对各键裂解能的计算结果表明，Car—Cal键的裂解能高于Cal—Cal，Car—O醚键的裂解能高于Cal—O醚键。而惰质组结构模型中除C—O醚键外，各键的裂解能均高于镜质组，说明惰质组结构模型比镜质组有较高的热稳定性。     

Reactivity of alkyl iodides in molecular decomposition reactions

The experimental results for the concerted molecular decomposition of alkyl iodides RI to olefin and HI were analyzed in terms of the intersecting parabolas model (IPM). The activation energies (E) and rate constants (k) of the earlier unstudied reactions of the concerted molecular decomposition of RI were calculated on the basis of the enthalpy of the reaction and IPM algorithms. The factors that influence on E of RI decay were established: the enthalpy of the reaction, the energy of stabilization of radical R*, the length and force constant of the C—I bond, and the size of the halogen atom. The values of E and k for the backward reactions of HI addition to olefins were estimated.     

A new method for estimation of homolytic C-H bond dissociation enthalpies

In this work we have quantitatively analyzed substituent effects on the homolytic bond dissociation enthalpy of 79 different compounds using a method based on discrete distance dependent atomic contributions to a molecular property. The resulting empirical relationship can be used to predict C-H bond dissociation enthalpies (within +/-10 kJ mol(-1)) for molecules where resonance contributions and captodative stabilization are insignificant. For species where captodative stabilization of the corresponding C-centered radical is possible, the method clearly overestimates the C-H bond dissociation enthalpy.     

An Accurate Molecular Structure of Phenyl,the Simplest Aryl Radical

The phenyl radical (C₆H₅^.) is the prototypical σ‐type aryl radical and one of the most common aromatic building blocks for larger ring molecules. Using a combination of rotational spectroscopy of singly substituted isotopic species and vibrational corrections calculated theoretically, an extremely accurate molecular structure has been determined. Relative to benzene, the phenyl radical has a substantially larger C‐C_ipso‐C bond angle [125.8(3)° vs. 120°], and a shorter distance [2.713(3) Å vs. 2.783(2) Å] between the ipso and para carbon atoms.     

An Accurate Molecular Structure of Phenyl,the Simplest Aryl Radical

The phenyl radical (C₆H₅^.) is the prototypical σ‐type aryl radical and one of the most common aromatic building blocks for larger ring molecules. Using a combination of rotational spectroscopy of singly substituted isotopic species and vibrational corrections calculated theoretically, an extremely accurate molecular structure has been determined. Relative to benzene, the phenyl radical has a substantially larger C‐C_ipso‐C bond angle [125.8(3)° vs. 120°], and a shorter distance [2.713(3) Å vs. 2.783(2) Å] between the ipso and para carbon atoms.     

Spectrophotometric,Thermodynamic and Density Functional Studies of Charge Transfer Complex Between Benzhydryl Piperazine and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

The charge transfer complex of benzhydryl piperazine as donor with the π-acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinone has been studied spectrophotometrically in acetonitrile medium at different temperatures. On mixing the donor with acceptor, a reddish brown colored charge transfer complex is formed. Electronic absorption spectra of the complex show charge transfer bands at 587, 546 and 457 nm. The molecular composition of the complex was studied by applying Job’s continuous variation and spectrophotometric titration methods. These results support the formation of the complex in a 1:2 ratio. The Benesi–Hildebrand equation has been applied to compute the formation constant and molecular extinction coefficient. Thermodynamic parameters of the charge transfer complexation reaction (standard entropy, standard enthalpy and standard Gibbs free energy) have been calculated. The results of the spectrophotometric study demonstrated that the charge transfer complex formation is endothermic. The computational studies of the charge transfer complex were performed by using the Gaussian 09 W package of programs. The bond lengths, bond angles, dihedral angles, Mulliken atomic charges, molecular electrostatic potential maps and characterization of the highest occupied molecular orbital and lowest unoccupied molecular orbital surfaces of charge transfer complex were computed.     

杨梅酮的抗氧化活性

采用密度泛函理论(DFT)方法, 研究了杨梅酮的分子结构、电子结构和羟基离解焓, 并探讨了杨梅酮与OOCH₃·自由基发生反应的抗氧化机理. 自由基发生反应的抗氧化机理. 在M06-2X/6-31++G(d,p)的计算水平下, 得到了杨梅酮脱氢后各种自由基的相对能量、羟基离解焓、氢原子提取的活化能垒和速率常数. 计算结果表明杨梅酮的4'-OH位置具有最高的抗氧化活性. 杨梅酮4'-OH位置的高活性, 主要是由于4'位上脱氢后生成的羰基与相邻的羟基之间形成了稳定的氢键. 分子中的原子(AIM)理论分析表明, 这种氢键相互作用能够稳定氢提取过程中产生的自由基. 对杨梅酮抗氧化性机理的理论研究, 可为今后设计合成新型的具有更强活性的抗氧化物提供坚实的理论基础.     

A new method of determination of radii of ions with arbitrary effective charges

An equation for calculation of the radii of ions with an arbitrary effective charge has been derived. The ionic radii of halogens, chalcogens, and other atoms with different charges have been calculated. Under the assumption of pure ionic bond character, these values have been used for calculating the R ₁₂ distances for a large group of different molecules—halogens, interhalides, oxygen, chalcogens, and nitrogen and their compounds—by the previously derived equation for the a priori determination of internuclear distances. The error of calculation of the internuclear distance for halogens and interhalides is no more than 0.07 Å (3–4%). The internuclear distance in dihalogen cations Hal ₂ ⁺ and binary ionic molecules of p elements and their oxides and sulfides have been calculated. It has been demonstrated that the coordination (environment) of atoms should be taken into account and that there is a possibility of estimating the bond multiplicity and the character of bonding electron pairs in a molecule.     

Rg—HX(Rg=He,Ne;X=F,Cl,Br)分子间势的精确量子化学从头计算研究III.He—HBr

在用非迭代的三重激发项来校正CCSD的CCSD（T）理论水平下，采用aug-cc- pVQZ基函数对He—HBr的分子间势进行了系统的研究。结果表明：He—HBr以线型结 构存在。在极限基的情况下，复合物两种线型极小点结构He—H—Br和He—Br—H势 阱深分别为28.792 cm~(-1)和35.707 cm~(-1)，对应He原子到HBr分子质心的距离 R分别为0.407 nm和0.343 nm。讨论了不同的基函数和理论方法在研究此类弱束缚 态复合物的分子间势时的可靠性及其对结果的影响，同时也给出了热函数的解析形 式。