Topological analysis of the charge density response of a Ni4 cluster to a probe H2 molecule

1990 ◽  
Vol 1 (2) ◽  
pp. 201-221 ◽  
Author(s):  
J. Guo ◽  
D. E. Ellis ◽  
R. F. W. Bader ◽  
P. J. MacDougall
Keyword(s):  
Charge Density ◽  
Topological Analysis ◽  
Density Response ◽  
H2 Molecule

Revisiting the charge density analysis of 2,5-dichloro-1,4-benzoquinone at 20 K

2017 ◽  
Vol 73 (4) ◽  
pp. 654-659 ◽  
Author(s):  
Zhijie Chua ◽  
Bartosz Zarychta ◽  
Christopher G. Gianopoulos ◽  
Vladimir V. Zhurov ◽  
A. Alan Pinkerton
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Topological Analysis ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Total Electron Density ◽  
Total Electron ◽  
Structure Factors ◽  
Density Analysis ◽  
Experimental Charge Density

A high-resolution X-ray diffraction measurement of 2,5-dichloro-1,4-benzoquinone (DCBQ) at 20 K was carried out. The experimental charge density was modeled using the Hansen–Coppens multipolar expansion and the topology of the electron density was analyzed in terms of the quantum theory of atoms in molecules (QTAIM). Two different multipole models, predominantly differentiated by the treatment of the chlorine atom, were obtained. The experimental results have been compared to theoretical results in the form of a multipolar refinement against theoretical structure factors and through direct topological analysis of the electron density obtained from the optimized periodic wavefunction. The similarity of the properties of the total electron density in all cases demonstrates the robustness of the Hansen–Coppens formalism. All intra- and intermolecular interactions have been characterized.

scholarly journals Structural analysis and multipole modelling of quercetin monohydrate – a quantitative and comparative study

2010 ◽  
Vol 67 (1) ◽  
pp. 63-78 ◽  
Author(s):  
Sławomir Domagała ◽  
Parthapratim Munshi ◽  
Maqsood Ahmed ◽  
Benoît Guillot ◽  
Christian Jelsch
Keyword(s):  
Comparative Study ◽  
Charge Density ◽  
Topological Analysis ◽  
Atomic Displacement ◽  
X Ray Diffraction ◽  
Experimental Database ◽  
Figures Of Merit ◽  
Atom Model ◽  
Atomic Displacement Parameters ◽  
Model Approach

The multipolar atom model, constructed by transferring the charge-density parameters from an experimental or theoretical database, is considered to be an easy replacement of the widely used independent atom model. The present study on a new crystal structure of quercetin monohydrate [2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-one monohydrate], a plant flavonoid, determined by X-ray diffraction, demonstrates that the transferred multipolar atom model approach greatly improves several factors: the accuracy of atomic positions and the magnitudes of atomic displacement parameters, the residual electron densities and the crystallographic figures of merit. The charge-density features, topological analysis and electrostatic interaction energies obtained from the multipole models based on experimental database transfer and periodic quantum mechanical calculations are found to compare well. This quantitative and comparative study shows that in the absence of high-resolution diffraction data, the database transfer approach can be applied to the multipolar electron density features very accurately.

scholarly journals Charge density analysis of paracetamol, acetotoluidine and methacetin

2014 ◽  
Vol 70 (a1) ◽  
pp. C541-C541
Author(s):  
Dmitry Druzhbin ◽  
Tatiana Drebushchak ◽  
Elena Boldyreva
Keyword(s):  
Charge Density ◽  
Topological Analysis ◽  
Intramolecular Interactions ◽  
Amide Bond ◽  
Electrostatic Energy ◽  
X Ray Diffraction ◽  
Methyl Group ◽  
Point Of Interest ◽  
Density Analysis ◽  
Topological Characteristics

Paracetamol (p-hydroxyacetanilide, Pbca), acetotoluidine (p-methylacetanilide, P21/c) and methacetin (p-methoxyacetanilide, Pbca) contain acetamide group included in molecular fragments, which play an important role in many drugs and proteins. As all of them are derivatives of acetanilide used in medicine, and due to the presence of the amide bond, their charge density analysis is important for better understanding amide infinite peptide chains. Thus, comparing the data obtained for paracetamol with acetotoluidine and with methacetin charge density data can provide deeper insight into NH···O bonding. Another point of interest is the possibility of methyl group rotation that remains to be ambiguous in these acetanilide molecule based compounds. In the present study we have attempted to elucidate these problems using precise X-ray diffraction at 100K with subsequent charge density topological analysis. All charge density refinements were based on the Hansen and Coppens multipolar atom model. The topologies of the inter- and intramolecular interactions are carefully analyzed for compounds. The atomic charges, bond orders, and the electrostatic energy in molecules are discussed. The topological characteristics in the critical point of the NH···O bond of paracetamol, acetotoluidine and methacetin are shown in the table below. In contrast to similarity in NH···O bonds for all studied compounds, intermolecular interactions between the double bonded oxygen atom and the hydrogen of dimer's methyl group are different. In acetotoluidine and methacetin the (3, –1) critical points with the same topological characteristics were detected between these atoms. In comparison to them, paracetamol with disordered methyl group [1, 2] has no such point. That can be related to the absence of the methyl group disorder in acetotoluidine and methacetin.

Doxycycline hydrate and doxycycline hydrochloride dihydrate – crystal structure and charge density analysis

2018 ◽  
Vol 233 (9-10) ◽  
pp. 649-661 ◽  
Author(s):  
Daniel Tchoń ◽  
Anna Makal ◽  
Matthias Gutmann ◽  
Krzysztof Woźniak
Keyword(s):  
Charge Density ◽  
Topological Analysis ◽  
Crystal Form ◽  
X Ray Diffraction ◽  
Neutron Data ◽  
Distribution Models ◽  
Crystal Forms ◽  
Density Analysis ◽  
Resonance Assisted Hydrogen Bond ◽  
Amide Nitrogen Atom

Abstract High-resolution low-temperature X-ray diffraction experiments for doxycycline monohydrate and hydrochloride dihydrate have been performed. Translation-Libration-Screw (TLS) analysis for both crystal forms as well as the data from neutron diffraction experiment for hydrochloride combined with the Hansen-Coppens formalism resulted in precise charge density distribution models for both the zwitterionic monohydrate and a protonated hydrochloride crystal forms. Their detailed topological analysis suggested that the electron structure of doxycycline’s amide moiety undergoes significant changes during protonation due to formation of a very strong resonance-assisted hydrogen bond. A notably increased participation of amide nitrogen atom and hydrogen-accepting oxygen atom in the resonance upon doxycycline protonation was observed. A comparison of TLS- and neutron data-derived hydrogen parameters confirmed the experimental neutron data to be vital for proper description of intra- and inter-molecular interactions in this compound. Finally, calculated lattice and interaction energies quantified repulsive Dox-Dox interactions in the protonated crystal form of the antibiotic, relating with a good solubility of doxycycline hydrochloride relative to its hydrate.

Topological analysis of the charge density of solids:bcc sodium and lithium

1993 ◽  
Vol 48 (5) ◽  
pp. 287-293 ◽  
Author(s):  
Changjiang Mei ◽  
Kenneth E. Edgecombe ◽  
Vedene H. Smith ◽  
A. Heilingbrunner
Keyword(s):  
Charge Density ◽  
Topological Analysis

Charge Density and Topological Analysis of Pentafluorobenzoic Acid

2001 ◽  
Vol 105 (31) ◽  
pp. 7405-7412 ◽  
Author(s):  
Ansgar Bach ◽  
Dieter Lentz ◽  
Peter Luger
Keyword(s):  
Charge Density ◽  
Topological Analysis ◽  
Pentafluorobenzoic Acid

Topological analysis of electron density and the electrostatic properties of isoniazid: an experimental and theoretical study

2014 ◽  
Vol 70 (2) ◽  
pp. 331-341 ◽  
Author(s):  
Gnanasekaran Rajalakshmi ◽  
Venkatesha R. Hathwar ◽  
Poomani Kumaradhas
Keyword(s):  
Hydrogen Bonding ◽  
Charge Density ◽  
Electron Density ◽  
Topological Analysis ◽  
Bond Critical Point ◽  
Potential Region ◽  
Electrostatic Properties ◽  
Structural And Electronic Properties ◽  
Density Analysis ◽  
Mycobacterial Cell Wall

Isoniazid (isonicotinohydrazide) is an important first-line antitubercular drug that targets the InhA enzyme which synthesizes the critical component of the mycobacterial cell wall. An experimental charge-density analysis of isoniazid has been performed to understand its structural and electronic properties in the solid state. A high-resolution single-crystal X-ray intensity data has been collected at 90 K. An aspherical multipole refinement was carried out to explore the topological and electrostatic properties of the isoniazid molecule. The experimental results were compared with the theoretical charge-density calculations performed usingCRYSTAL09with the B3LYP/6-31G** method. A topological analysis of the electron density reveals that the Laplacian of electron density of the N—N bond is significantly less negative, which indicates that the charges at the b.c.p. (bond-critical point) of the bond are least accumulated, and so the bond is considered to be weak. As expected, a strong negative electrostatic potential region is present in the vicinity of the O1, N1 and N3 atoms, which are the reactive locations of the molecule. The C—H...N, C—H...O and N—H...N types of intermolecular hydrogen-bonding interactions stabilize the crystal structure. The topological analysis of the electron density on hydrogen bonding shows the strength of intermolecular interactions.

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