X-ray molecular structure and theoretical study of 1,4-bis[2-cyano-2-(o-pyridyl)ethenyl]benzene

2014 ◽  
Vol 68 (2) ◽  
Author(s):  
M. Percino ◽  
Maria Castro ◽  
Margarita Ceron ◽  
Guillermo Soriano-Moro ◽  
Victor Chapela ◽  
...  
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Chloroform Solution ◽  
Monoclinic System ◽  
Functional Theory ◽  
Torsion Angles ◽  
X Ray ◽  
Structural Characterisation ◽  
Phenyl Rings ◽  
Moller Plesset

AbstractThe structural characterisation of the molecule 1,4-bis[2-cyano-2-(o-pyridyl)ethenyl] benzene obtained through Knoevenagel condensation is reported. The single crystals, as light brown rods, were cultured from a chloroform solution using a slow evaporation method at ambient temperature. The compound crystallised in the monoclinic system belonging to the C2/c space group with a = 26.4556(9) Å, b = 3.73562(10) Å, c = 18.4230(6) Å, β = 109.841(4)° and the asymmetric unit comprising Z = 4. The structure is ordered and the molecules of the title compound exhibited a lattice with water molecules located at sites of inversion and two-fold axial symmetries. Thus, only halves of the molecules are symmetrically independent. The lattice is reported and contrasted with X-ray single-crystal diffraction and theoretical calculations of 1,4-bis(1-cyano-2-phenylethenyl)benzene. By using density functional theory (DFT) and second order Moller-Plesset (MP2) theoretical calculations, the ground state geometry in the whole molecule at the B3LYP/6-31+G(d,p), and MP2/6-31+G(d,p) theory levels, respectively, were optimised. The DFT calculations showed a quasi-planar structure of the molecule, whereas the wave function-based MP2 method afforded a non-planar optimised structure with significant torsion angles between the pyridine and phenyl rings.

scholarly journals Size Matters: New Zintl Phase Hydrides of REGa (RE = Y, La, Tm) and RESi (RE = Y, Er, Tm) with Large and Small Cations

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 600
Author(s):  
Werwein ◽  
Hansen ◽  
Kohlmann
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Structural Diversity ◽  
Type Structure ◽  
Zintl Phases ◽  
Structure Form ◽  
Functional Theory ◽  
X Ray ◽  
Hydrogenation Reactions ◽  
Tetrahedral Voids

Many Zintl phases exhibiting a CrB type structure form hydrides. Systematic studies of AeTtHx (Ae = Ca, Sr, Ba; Tt = Si, Ge, Sn), LnTtHx (Ln = La, Nd; Tt = Si, Ge, Sn), and LnGaHx (Ln = Nd, Gd) showed the vast structural diversity of these systems. Hydrogenation reactions on REGa (RE = Y, La, Tm) and RESi (RE = Y, Er, Tm) were performed in steel autoclaves under hydrogen pressure up to 5 MPa and temperatures up to 773 K. The products were analyzed by X-ray and neutron powder diffraction. RESi (RE = Y, Er, Tm) form hydrides in the C-LaGeD type. LaGaD1.66 is isostructural to NdGaD1.66 and shows similar electronic features. Ga-D distances (1.987(13) Å and 2.396(9) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. In TmGaD0.93(2) with a distorted CrB type structure deuterium atoms exclusively occupy tetrahedral voids. Theoretical calculations on density functional theory (DFT) level confirm experimental results and suggest metallic properties for the hydrides.

Substituent effects intrans-p,p′-disubstituted azobenzenes: X-ray structures at 100 K and DFT-calculated structures

2014 ◽  
Vol 70 (6) ◽  
pp. 575-579 ◽  
Author(s):  
Katarzyna Gajda ◽  
Bartosz Zarychta ◽  
Zdzisław Daszkiewicz ◽  
Andrzej A. Domański ◽  
Krzysztof Ejsmont
Keyword(s):  
Benzene Ring ◽  
Density Functional ◽  
Substituent Effects ◽  
Molecular Structures ◽  
Functional Theory ◽  
Torsion Angles ◽  
X Ray ◽  
Aromaticity Index ◽  
Homologous Compounds ◽  
Isolated Molecules

The crystal and molecular structures of twopara-substituted azobenzenes with π-electron-donating –NEt2and π-electron-withdrawing –COOEt groups are reported, along with the effects of the substituents on the aromaticity of the benzene ring. The deformation of the aromatic ring around the –NEt2group inN,N,N′,N′-tetraethyl-4,4′-(diazenediyl)dianiline, C20H28N4, (I), may be caused by steric hindrance and the π-electron-donating effects of the amine group. In this structure, one of the amine N atoms demonstrates clearsp2-hybridization and the other is slightly shifted from the plane of the surrounding atoms. The molecule of the second azobenzene, diethyl 4,4′-(diazenediyl)dibenzoate, C18H18N2O4, (II), lies on a crystallographic inversion centre. Its geometry is normal and comparable with homologous compounds. Density functional theory (DFT) calculations were performed to analyse the changes in the geometry of the studied compounds in the crystalline state and for the isolated molecules. The most significant changes are observed in the values of the N=N—C—C torsion angles, which for the isolated molecules are close to 0.0°. The HOMA (harmonic oscillator model of aromaticity) index, calculated for the benzene ring, demonstrates a slight decrease of the aromaticity in (I) and no substantial changes in (II).

scholarly journals Synthesis of Pure NiTiSn by Mechanical Alloying: An Investigation of the Optimal Experimental Conditions Supported by First Principles Calculations

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 835 ◽  
Author(s):  
Monique Tillard ◽  
Alexandre Berche ◽  
Philippe Jund
Keyword(s):  
Mechanical Alloying ◽  
Density Functional ◽  
Annealing Temperature ◽  
Theoretical Calculations ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Functional Theory ◽  
X Ray ◽  
Careful Investigation

Synthesis of NiTiSn by a mechanical alloying process followed by a high temperature thermal annealing was studied. Experiments were conducted varying parameters like the provided energy, the mechanical alloying reaction time, as well as the annealing temperature and duration. Based on the careful investigation of the phases present in the samples by systematic X-ray diffraction (after mechanical alloying and after annealing) and selected microscopy analyses, a reaction mechanism is proposed supported by theoretical calculations at the DFT (Density Functional Theory) level. An energy window to prepare directly NiTiSn has been evidenced. Highly pure NiTiSn has also been obtained by conversion from a multicomponent precursor obtained by low energy mechanical alloying.

scholarly journals Solid-state structure of cyclic dipeptides: an X-ray and computational study of cis- and trans-diketopiperazines of N-methyl-phenylalanine with the thia-pipecolic acids and thia-prolines

2017 ◽  
Vol 73 (6) ◽  
pp. 1179-1193 ◽  
Author(s):  
Milos Budesinsky ◽  
Ivana Cisarova ◽  
Frans Borremans ◽  
Jose C. Martins ◽  
Ewald Pauwels
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Density Functional Theory Calculations ◽  
Amide Bond ◽  
Functional Theory ◽  
Torsion Angles ◽  
Molecular Conformations ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cis And Trans

Ten new crystal structures of cis and trans bicyclic diketopiperazines (DKPs) of thia-pipecolic acid (with sulfur in the β, γ or δ position) or thia-proline (with sulfur in the β or γ position) and N-methyl phenylalanine [(NMe)Phe]: cyclo[(β-S)Pip-(NMe)Phe], cyclo[(γ-S)Pip-(NMe)Phe], cyclo[(δ-S)Pip-(NMe)Phe], cyclo[(β-S)Pro-(NMe)Phe] and cyclo[(γ-S)Pro-(NMe)Phe] were determined with X-ray crystallography. Density functional theory calculations of these molecules in the gas phase succeed in reproducing the observed molecular conformations in the crystal remarkably well. This illustrates the weak to moderate impact of intermolecular packing forces in the absence of classical N—H...O hydrogen bonds. The effect of sulfur on the geometry of the DKP ring and details of amide bond non-planarity are discussed. Molecular flexibility of the DKP ring, as estimated from the calculated deformation energies of its endocyclic ring torsion angles, is not in general the decisive factor for the occurrence of multiple symmetry independent molecules in the unit cell (Z′ > 1), though in some cases a correlation is observed.

scholarly journals Theoretical Investigation of the Quasi-ring C–H…π Interactions

2021 ◽  
Vol 18 (2) ◽  
pp. 119-128
Author(s):  
Sin Ang Lee ◽  
◽  
Zaidi Ab Ghani ◽  
Mohd Hafiz Yaakob ◽  
Mohamed Ismail Mohamed-Ibrahim ◽  
...  
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Basis Set ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Crystalline Materials ◽  
Π Interactions ◽  
Linear Chains ◽  
Moller Plesset ◽  
The Stability

The quasi-ring C–H…π interactions have been reported to be responsible for the stability of crystalline materials. The statistical analysis, together with electronic structure calculations in the framework of density functional theory and Moller-Plesset have also provided positive data on the aforementioned interactions. However, improvements can be had in the theoretical calculations, where the basis set convergence is not explored. This is crucial as the interactions are of weak type, reported to be around 4 – 5 kcal mol–1. In this investigation, the idea is to combine the geometry, potential energy surface, and bonding analysis to provide different insights into the interactions. Our results show that the original configurations of the crystals, even with the substitutions of linear chains, are more favorable than the rotated ones. Further calculations are needed to verify the involvements of the π orbitals of the N, C, Cl, S and the d-orbital of Cu, and the s-orbital of hydrogen atoms.

Steric and electronic evaluations of P(o-tol)R 2, where R is phenyl or cyclohexyl: crystal structures of SeP(o-tol)R 2

2019 ◽  
Vol 75 (9) ◽  
pp. 1310-1318
Author(s):  
Wade L. Davis ◽  
Alfred Muller
Keyword(s):  
Crystal Structures ◽  
Density Functional ◽  
Coupling Constants ◽  
Monoclinic Crystal ◽  
Functional Theory ◽  
Torsion Angles ◽  
X Ray ◽  
Unit Cells ◽  
Geometrical Data ◽  
Packing Arrangement

The crystal structures of SeP(o-tol)R 2, where o-tol is ortho-tolyl (2-methylphenyl) and R is Ph (phenyl), namely (2-methylphenyl)diphenylphosphane selenide, C19H17PSe, or Cy (cyclohexyl), namely dicyclohexyl(2-methylphenyl)phosphane selenide, C19H29PSe, were determined to aid in the evaluation of the steric and electronic behaviour of these analogous phosphane compounds. The compounds crystallized in similar monoclinic crystal systems, but are differentiated in their unit cells by a doubling of the number of independent molecules for R = Cy (Z′ = 2) and the choice of glide plane by convention. The preferred orientation for the o-tolyl substituent obtained from the X-ray structural analysis is gauche for R = Ph and anti for R = Cy (using the Se—P—C ipso —C ortho torsion angles as reference). Density functional theory (DFT) calculations showed both conformations to be equally probable and indicate that the preferred solid-state conformer is probably due to the minimization of repulsion energies, resulting in a packing arrangement primarily featuring weak C—H...Se interactions and additional C—H...π interactions in the R = Ph structure. A detailed electronic and steric analysis was conducted on both phosphanes using Se—P bond lengths, multinuclear NMR 1 J Se–P coupling constants, theoretical topological evaluation and crystallographic and solid-angle calculations, and compared to selected literature examples. The results indicate that the use of the o-tolyl substituent increases both the electron-donating capability and the steric size, but is also dependent on whether the o-tolyl group adopts a gauche or anti conformation. The single-crystal geometrical data are unable to detect electronic differences between these two structures due to the somewhat large displacement parameters observed for the Se atom in the R = Cy structure.

Tracking the dissolution–recrystallization structural transformation (DRST) of copper(II) complexes: a combined crystallographic, mass spectrometric and DFT study

2020 ◽  
Vol 76 (7) ◽  
pp. 655-662
Author(s):  
Qian-Jun Deng ◽  
Min Chen ◽  
Dong-Chu Chen ◽  
Hang-Yu Long ◽  
Chang-Ai Chen
Keyword(s):  
Mass Spectrometry ◽  
Structural Transformation ◽  
Density Functional ◽  
Electrospray Mass Spectrometry ◽  
Theoretical Calculations ◽  
Binuclear Copper ◽  
Functional Theory ◽  
X Ray ◽  
X Ray Crystallography ◽  
First Time

Methanol- and temperature-induced dissolution–recrystallization structural transformation (DRST) was observed among two novel CuII complexes. This is first time that the combination of X-ray crystallography, mass spectrometry and density functional theory (DFT) theoretical calculations has been used to describe the fragmentation and recombination of a mononuclear CuII complex at 60 °C in methanol to obtain a binuclear copper(II) complex. Combining time-dependent high-resolution electrospray mass spectrometry, we propose a possible mechanism for the conversion of bis(8-methoxyquinoline-κ2 N,O)bis(thiocyanato-κN)copper(II), [Cu(NCS)2(C10H9NO)2], Cu1, to di-μ-methanolato-κ4 O:O-bis[(8-methoxyquinoline-κ2 N,O)(thiocyanato-κN)copper(II)], [Cu2(CH3O)2(NCS)2(C10H9NO)2], Cu2, viz. [Cu(SCN)2(L)2] (Cu1) → [Cu(L)2] → [Cu(L)]/L → [Cu2(CH3O)2(NCS)2(L)2] (Cu2). We screened the antitumour activities of L (8-methoxyquinoline), Cu1 and Cu2 and found that the antiproliferative effect of Cu2 on some tumour cells was much greater than that of L and Cu1.

scholarly journals Theoretical Calculations for the Acidity of Cyanopolyynes HC2n+1N (n = 0–5) in Gas and Aqueous Phases Using Ab initio Methods

2019 ◽  
Vol 7 (1) ◽  
pp. 27
Author(s):  
Hassan H. Abdallah
Keyword(s):  
Gas Phase ◽  
Aqueous Phase ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Dust Cloud ◽  
Basis Set ◽  
Ab Initio Methods ◽  
Functional Theory ◽  
Moller Plesset ◽  
Cold Dust

Cyanopolyynes have been found in the interstellar medium, cold dust cloud Taurus Molecular Cloud-1, and the Titan’s atmosphere. Theoretical calculations are carried out to predict gas and aqueous phase acidities of a series of cyanopolyynes acids. Two levels of theory were used in this study, with the combination of density functional theory, and Møller–Plesset perturbation (MP2) theory, MP2 methods with two types of basis set, namely, Pople’s 6–311++g (d, p) basis set and Dunning’s aug-cc-pVTZ basis set. The calculations of these molecules reveal that pKa values varying from 12.25 to 17.25 and indicate that the acidity of these molecules in aqueous phase increases whereas the acidity in gas phase decreases with an increasing chain length of these acids.

Theoretical and Experimental Evaluation of the Effect of Fluorinated Substituent on the Topological Landscape and Thermodynamic Stability of Zeolitic Imidazolate Framework Polymorphs

2018 ◽  
Author(s):  
Mihails Arhangelskis ◽  
Athanassis Katsenis ◽  
Novendra Novendra ◽  
Zamirbek Akimbekov ◽  
Dayaker Gandrath ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Mechanochemical Synthesis ◽  
Thermodynamic Stability ◽  
Experimental Evaluation ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Zeolitic Imidazolate Framework ◽  
Functional Theory ◽  
Calorimetric Measurements ◽  
And Calorimetry

By combining mechanochemical synthesis and calorimetry with theoretical calculations, we demonstrate that dispersion-corrected periodic density functional theory (DFT) can accurately survey the topological landscape and predict relative energies of polymorphs for a previously inaccessible fluorine-substituted zeolitic imidazolate framework (ZIF). Experimental screening confirmed two out of three theoretically anticipated polymorphs, and the calorimetric measurements provided an excellent match to theoretically calculated energetic difference between them.<br>

Highly Electron-Deficient Pyridinium-Nitrones for Rapid and Tunable Inverse-Electron-Demand Strain-Promoted Alkyne-Nitrone Cycloaddition to Bicyclo[6.1.0]nonyne

2019 ◽  
Author(s):  
Praveen Gunawardene ◽  
Wilson Luo ◽  
Alexander M. Polgar ◽  
John F. Corrigan ◽  
Mark Workentin
Keyword(s):  
Density Functional Theory ◽  
Reaction Kinetics ◽  
Density Functional ◽  
Functional Theory ◽  
X Ray ◽  
Inverse Electron Demand ◽  
X Ray Crystallography ◽  
Electron Demand

<div> <div> <p>Highly accelerated inverse-electron-demand strain-promoted alkyne-nitrone cycloaddition (IED SPANC) between a sta- ble cyclooctyne (bicyclo[6.1.0]nonyne (BCN)) and nitrones delocalized into a Cα-pyridinium functionality is reported, with the most electron-deficient “pyridinium-nitrone” displaying among the most rapid cycloadditions to BCN that is currently reported. Density functional theory (DFT) and X-ray crystallography are explored to rationalize the effects of N- and Cα-substituent modifications at the nitrone on IED SPANC reaction kinetics and the overall rapid reactivity of pyridinium-delocalized nitrones.</p> </div> </div>

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