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Bzhezovskii, V. M.; Kapustin, E. G.

doi:10.1023/a:1016559525299

Cited by 14 publications

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“…One lone electron pair is a hybrid orbital (n s ), and the other, virtually pure p x orbital (n p ). In the hybrid orbitals of the lone electron pairs n s , the These values are close to those obtained previously in the series of aromatic [16] and vinyl [17] compounds with the corresponding heteroatoms. According to the results given in Table 1, in terms of the NBO formalism, n s and n p of the X atoms appreciably differ in the energy.…”

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An ab initio quantum-chemical study of the compounds HC≡CXCH3 (X = O, S, Se)

et al. 2004

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The compounds HC=CXMe (X = O, S, Se) were studied by the MP2(full)/6-31G* ab initio method using the method of natural bond orbitals. The parameters of the molecular geometry were obtained. The electron density distribution in these compounds is determined to a greater extent by the electronegativity of atoms X, than by conjugation of the lone electron pairs of the heteroatoms with the triple bond.Chemical transformations of acetylene and its derivatives allow preparation of new promising monomers, cross-linking agents, and intermediates for fine organic synthesis [1,2]. Understanding of the factors affecting the reactivity of the compounds and development of new synthetic routes are impossible without comprehensive study of their electronic and steric structure by physicochemical and theoretical methods. Modern ab initio quantum-chemical methods taking into account the electron correlation reproduce the experimentally observed molecular characteristics with a high accuracy, without introducing any empirical fitting parameters [3]. Analysis of the wave functions obtained by the method of natural bond orbitals (NBO) allows transformation of the canonical molecular orbitals into orbitals of the Lewis type and interpretation of the results of quantum-chemical calculations in terms of traditional chemistry [4 3 6].Our goal was to apply this approach to the compounds HC=CXMe (X = O, S, Se) and to analyze the quantitative information on the nature of the lone electron pairs of the O, S, and Se atoms, on their interaction with the triple bond, and on their effect on the electron density distribution.Our study was based on ab initio quantum-chemical calculations taking into account the correlation energy for all the electrons on the level of the secondorder Møller3Plesset perturbation theory [3,7] in the 6-31G double-split basis set with six d functions [8]: MP2(full)/6-31G*. The calculations were performed using the GAUSSIAN 98W (Rev. A.7) [9] and GAMESS [10] software. We used standard criteria of convergence of the density matrix and energy gradient. The population analysis of the wave functions was performed with the NBO method [4 3 6]. We obtained the following total energies (E t , au): 3191.2592574 (HC=COMe), 3513.8919695 (HC=CS . Me), and 32514.0062393 (HC=CSeMe). For HC b =C a . OMe, the COC bond angle (113.4o) and the C sp 3O (1.313 A) and C sp 33O (1.434 A) bond lengths have been determined experimentally [11, 12]. We obtained the following structural parameters for this molecule: 112.9o (UCOC); 1.217 [d(C=C)], 1.315 [d(C a 3X)], 1.064 [d(C b 3H)], 1.445 [d(X3CMe)], and 1.088, 1.092, 1.092 A [d(C3H Me )]. The steric structure of HC b =C a SMe was studied by electron diffraction [13] and microwave spectroscopy [14]. The C=C bond length is 1.215(3) [13] or 1.205(7) A [14]; the C sp 3S bond length is 1.683(3) [13] or 1.685(5) A [14], and the C sp 33S bond length, 1.814(3) [13] and 1.813(2) A [14]. The CSC bond angle is 99.9o [13, 14], and the SCC bond angle, 184(3)o [13] or 182(0.3)o [14]. We obtained the followin...

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“…and Se atoms with the acetylenic moiety exceeds the energy of the resonance interaction of n p of the respective heteroatoms with the aromatic ring in the C 6 H 5 XMe molecules [16] and with the double bond in the H 2 C=CHXMe molecules [17].…”

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An ab initio quantum-chemical study of the compounds HC≡CXCH3 (X = O, S, Se)

et al. 2004

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“…As a result, the most stable structure of 3 is one in which the methyl moieties are almost perpendicular to the planar 4TA core, consistent with the molecular structures elucidated by single-crystal X-ray analysis (Figure c). The difference in the stable conformation depending on the chalcogen atoms can be explained by the nature of the lone electron pairs of the chalcogen atoms that largely affect the intramolecular n -π* interaction . The oxygen atom in the methoxy group effectively contributes to the intramolecular n -π* interaction that stabilizes the coplanar structure; however, the larger the chalcogen atoms, the lesser the contribution to the intramolecular n -π* interaction.…”

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confidence: 99%

Crystal Structures of β-Methylchalcogenated Tetrathienoacenes: From One-Dimensional π-Stacking to Sandwich Pitched π-Stacking Structure

Takimiya

Kanazawa

Kawabata

2021

Crystal Growth & Design

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The control and prediction of crystal structures of molecular semiconductors is critical to optimize such solid-state properties as carrier mobility, although it still presents a challenge owing to the complicated interplay of various intermolecular interactions in the solid state. We recently reported that methylthio and methoxy groups can act as a "controller" of crystal structure from the herringbone to the rubrene-like pitched π-stacking in a series of acenedithiophenes and simple acenes, such as naphthalene and anthracene. In this study, we focused on tetrathienoacene (4TA), which affords a one-dimensional πstacking structure, and investigated the effect of methylchalcogenation on its crystal structure. The crystal structures of newly synthesized 4TA derivatives were altered significantly; the methoxy and methylthio derivatives crystallized into a "sandwiched pitched π-stacking" structure, whereas the methylseleno 4TA crystallized into a "pseudo π-stacking" structure. These structural changes were explained by the analysis of intermolecular interactions estimated by the symmetry-adapted perturbation theory method. The interplay between the CH-π interactions induced by the methylchalcogenation and the inherent nature of the π-π interactions of the 4TA cores determined the crystal structures of the 4TA derivatives. We conclude that the mutual effects of the parent π-conjugated system and the methylchalcogeno groups are important to define the packing structure.

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“…This is governed by the weighted average value of the torsion angles ϑ and Ψ at the bonds Х-C α and Х-C ipso (Х = S, Se) respectively (see structure А). The analysis of the intramolecular interactions in phenyl and vinyl sulfi des and selenides in the framework of the formalism of the Natural Bond Orbitals,NBO [13] showed that the energy of the interaction of the unshared electron pairs of sulfur or selenium atoms with the π*-orbitals of the double bond is signifi cantly higher than the interaction with the π*-orbitals of the aromatic ring [4,14]. This fact results in considerably larger value of the weighted average torsion angle Ψ than ϑ, and in the sterically strained s-cis-conformation of molecules I and II the torsion angle Ψ should be especially large [15,16].…”

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Through space spin-spin coupling 19F-1H as the base for comparative analysis of conformational equilibrium in fluorine-substituted aryl vinyl selenides and sulfides

Afonin

2010

Russ J Org Chem

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The analysis of long-range spin-spin coupling 19 F-1 H and the other conformation-dependent parameters of 1 Н NMR spectra shows that aryl vinyl selenides like aryl vinyl sulfi des exist as mixtures of s-cis and s-trans rotational isomers. The combined data of 1 Н and 13 С NMR spectra reveal the increase in the torsional angle ϑ at the bond Х-СН=СН 2 (Х = S, Se) in selenides compared to sulfi des due to diminished interaction energy of the unshared electron pairs of selenium with the π*-orbitals of the double bond as compared to analogous interaction in sulfi des.In the course of recent decades the phenomenon of the rotational isomerism in vinyl chalcogenides was subjected to thorough study by means of versatile physicochemical methods and quantum-chemical calculations [1, 2]. These investigations made it possible to estimate reliably the quantitative content and to study the features of the spatial arrangement of various conformers of vinyl ethers and sulfi des possessing a wide range of substituents. At the same time the rotationsl isomerism in vinyl selenides was considered only occasionally due to the limited number of the synthetically available compounds. In [3] the rotational isomerism of methyl vinyl selenide was studied by the temperature dependence of the characteristic absorption bands in the IR spectra. It was demonstrated that the methyl vinyl selenide existed as a mixture of rotatonal isomers among which the most stable was the fl at s-cisconformer [3]. This conclusion was later confi rmed by quantum-chemical calculations on the level MP2/6-31(d) that revealed the presence of the main minimum on the curve of potential energy of internal rotation corresponding to the s-cis-form [4]. The second minimum of the methyl vinyl selenide corresponded to two degenerate gauche-forms divided by a relatively small energy barrier (~0.5 kcal mol -1 ) in the region of s-trans-form [4].The quantum-chemical calculation on the level MP2/6-311(d,р) and the analysis of coupling constants 77 Se-1 H in divinyl selenide revealed that this compound exists as three rotational isomers: non-fl at s-cis/s-trans and two non-fl at s-trans/s-trans distinguished by the values of the torsional angles at the Se-C bonds [5]. Therewith the s-cis/s-trans-form is considerably more populated [5]. No data appeared in publications up till now concerning vinyl selenides with other substituents. In this study the rotational isomerism in aryl vinyl selenides was studied by the analysis of parameters of 1 H and 13 С NMR spectra.We formerly reported on a presence in the fl uorinesubstituted aryl vinyl sulfi des of a through-space longrange spin-spin coupling 19 F-1 H involving the protons of the vinyl group indicating that these compounds existed as a mixture of s-cis-and s-trans-rotational isomers [6]. The previously performed synthesis of 1,4-divinylseleno-2,3,5,6-tetrafl uorobenzene (I) [7] provided a possibility to apply this molecule as an object of such study in the series of aryl vinyl selenides. The parameters of 1 Н and 13 С spectra of t...

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Cited by 14 publications

References 14 publications

An ab initio quantum-chemical study of the compounds HC≡CXCH3 (X = O, S, Se)

An ab initio quantum-chemical study of the compounds HC≡CXCH3 (X = O, S, Se)

Crystal Structures of β-Methylchalcogenated Tetrathienoacenes: From One-Dimensional π-Stacking to Sandwich Pitched π-Stacking Structure

Through space spin-spin coupling 19F-1H as the base for comparative analysis of conformational equilibrium in fluorine-substituted aryl vinyl selenides and sulfides

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