Bond Lengths In Molecules Research Articles

The interference fringes of above-threshold ionization spectrum of SF6 molecules in an IR + XUV laser field

The interference fringes of above-threshold ionization (ATI) spectrum from atoms or molecules have been extensively studied. In this paper, we investigate the ATI of the polyatomic molecule SF6 in IR + XUV two-color laser fields, and find that some interference fringes on the spectrum are from the molecular structure, which is independent of the parameters of the laser field. Based on the frequency-domain theory, we analyze the interference fringes for different orbitals of SF6 molecules in detail. It is found that the orbital of SF6 can be simplified by several terms in the region of high value of momentum, where the destructive interference fringes from these terms may carry the information of the molecular structure. Furthermore, we obtain destructive interference formulas from these simplified orbitals, which may predict the interference fringes on the ATI spectrum. Additionally, we may obtain the information about the bond length of molecules. It will be useful for the study of the ionization spectrum of polyatomic molecules.

Спектральное и квантово-химическое изучение таутомерных и ионных превращений 2-(2-(2-гидрокси-5-сульфанилфенил) гидразон)-3-оксо-N-фенилбутанамида

In this paper, using the method DFT/B3LYP of quantum chemical modeling, the stability of tautomeric, conformer, and anionic forms of 2-(2-(2-hydroxy-5-sulfamoylphenyl)hydrazone-3-oxo-N-phenylbutanamide (H2L) was studied and the geometric, electronic structure and bond lengths of molecules in various tautomeric forms were determined. It was shown that the stability of tautomeric molecules H2L as anionic forms was determined by the number of existing intermolecular hydrogen bonds (closing six-membered and five-membered cycles). The most stable tautomeric and conformal forms of an organic molecule and its dianion are proposed. The interatomic distances, angles, charges on atoms, IR and electronic absorption spectra of tautomeric forms of the molecule and dianion (H2L and L2-) were calculated. In this work, we studied the electronic absorption spectra in an aqueous-alcoholic solution and found that in an alkaline medium the molecule transforms into the ionic form with a bathochromic shift of 47 nm, corresponding to the results of the shift of the long-wavelength band electronic absorption spectra upon transition from the hydrazotautomer (form a) to the dianion form (form b’’) at 92 nm obtained by TD-DFT. The calculated results for the distance and angles between atoms are in good agreement with the experimental data of the molecule by X-ray diffraction analysis. It was shown that the IR spectrum of the stable form appears two absorption bands in the region of 1690 and 1655 cm–1, which are attributed to stretching vibrations of carbonyl groups (C=O), bound by a strong intramolecular hydrogen bond and the presence of the NH-hydrazone fragment of the 1H NMR spectrum confirmed the most stable for a neutral molecule is the hydrazone form.

Dependence of the bond length in molecules and crystals on coordination numbers of atoms

Two approaches to the description of changes in the bond length in molecules and crystals with changing coordination number of atoms are studied. They are based on a difference or ratio of interatomic distances when the structure is changed. The second approach is shown to yield more accurate results. The change in the interatomic distances in polar compounds has the same character as the change in the ionic radii when coordination numbers are varied.

An investigation into adsorption of simple organic and inorganic molecules on a silica gel surface

Adsorption of simple organic and inorganic molecules on an amorphized silica gel surface is studied within the framework of density functional theory in the approximation of periodic crystalline slabs. Adsorption of water, ammonia, acetone, and ethanol molecules is examined. Most probable adsorption sites of molecules on the surface are calculated and the adsorption energies and bond lengths of molecules on the silica gel surface are estimated.

Hydrogen complexes of O-vinylacetoxime with trifluoroacetic acid

According to B3LYP/6-31G** calculations, the stable antiperi-, antiperiperiplanar and antiperi-, synperiperiplanar conformers of O-vinylacetoxime (1) form with trifluoroacetic acid strong H complexes of two types: with N···H-O and O···H-O hydrogen bonds. The former are more stable. Complexation changes N-O and C-O bond lengths in molecule 1, as well as mutual orientation of its vinyl and azomethine groups. The structural effect depends on the orientation of the H bond, which, in its turn, is determined by the nature of the electron-donor center. When the nitrogen atom of oxime 1 is involved in complex formation, the H bond lies in the molecular plane, whereas the H bond involving the oxygen atom is directed in parallel with its lone electron pair.

Dependence of energies on the bond lengths in molecules and crystals

The dependence of the binding energies in molecules and crystals on the interatomic distances near the equilibrium position was established in the framework of the Mie equation using the force constants of molecules and the elasticity moduli of solids. To evaluate the repulsion forces, we used the Morse function for molecules and the Born-Lande approach for ionic crystals.

Structures of Nucleobases Trapped within Au Triangles and Its Effects on Hydrogen Bonding in Base Pairs of DNA

Nucleobases (adenine (A), thymine (T), cytosine (C), and guanine (G)) trapped within two metal clusters such as Au(3) undergo expansion. Our investigation reveals that this primarily arises due to the concomitant increase in all the bond lengths in molecules. Such expansion of the molecules can be qualitatively understood on the basis of classical harmonic potentials in the bonds and loss of aromaticity in the rings. Specifically, the highly electronegative O and N elements in the base pairs anchor to Au atoms and form X-Au bonds, which leads to charge redistribution within the molecules. As a very important consequence of this, the nature of the hydrogen bonds (in Au(3)-A...T-Au(3) and in Au(3)-G...C-Au(3)) change substantially within these electrodes in comparison to gas-phase structures. These hydrogen bonds have a single-well potential energy profile (of the type N...H...O and N...H...N) instead of double-well potentials (like N-H...O or N-H...N/ N...H-N types). A detailed energy calculation along the proton movement pathway supports our conclusions.

Manipulating bond lengths adiabatically with light

In this paper we propose a new method to manipulate bond lengths in molecules. The scheme uses strong fields that prepare an artificial potential with the desired equilibrium bond length, by controlling the mixing of electronic configurations, and finds an adiabatic path that connects the initial state with the laser created potential. As an illustration, we show that it is possible to control the bond length of a diatomic molecule by directly coupling the ground state and a dissociative potential, with the aid of a second excited bound potential.

Atom sizes and bond lengths in molecules and crystals

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAtom sizes and bond lengths in molecules and crystalsMichael O'Keefe and N. E. BreseCite this: J. Am. Chem. Soc. 1991, 113, 9, 3226–3229Publication Date (Print):April 1, 1991Publication History Published online1 May 2002Published inissue 1 April 1991https://doi.org/10.1021/ja00009a002RIGHTS & PERMISSIONSArticle Views2581Altmetric-Citations454LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (453 KB) Get e-Alerts Get e-Alerts

Study of the structure of azatetrahedranes by quantum-chemical methods

In the present work we studied the geometric structure of tetrahedrane (I), azatetrahedrane (II), diazatetrahedrane (III), triazatetrahedrane (IV), and tetraazatetrahedrane (V) (see Fig. i). The data available from the literature on the structure of these compounds, with the exception of the parental hydrocarbon [5], are basically results obtained by the MINDO/3 method and a nonempirical method in a minimal basis. However, the MINDO/3 method is known to be unsuitable for calculations of compounds with NN bonds, and the latter method is known to be unsuitable for the determination of the structure of stressed compounds. We carried out the optimization of the geometry of molecules I-V by a nonempirical method in the 3-21G basis [6], whose accuracy in the determination of bond lengths in organic molecules is comparable to experimental accuracy. The GAUSSIAN-80 system of programsadapted for the ES1052 computer was used. In addition, semiempirical calculations were performed by the MNDO method, as well as with the use of a variant of the MINDO/3 method with corrected values for the two-center parameters aNN and BNN, which has demonstrated its superiority over the ordinary versionof the method on an extensive group of nitrogen-containing compounds (MINDO/3M [7]). The data from the calculations of the bond lengths in the molecules studied are presented in Table I~ The data from [i, 2] (MINDO/3), [4, 8, 9] (MNDO), and [2] (STO-3G) were used in part in compiling this table. In the literature there are data from the calculation of bond lengths in double-zeta basis: The results for I in [5] differ only slightly from the values which we obtained, but the data for V in [3], which were obtained with the use of a pseudopotential, deviate significantly from the results presented. A possible reason for this disparity is the greater structural lability of the molecules of the tetrahedrane series, as well as the necessity of using gradient methods of optimization in carrying OUt nonempiri -~ cal structural calculations (see, for example, [i0]).