Probing the effect of electric field in 9,10-dimethoxy-2,6-bis(2-p-tolylethynyl)anthracene molecular nanowire using quantum chemical and charge density analysis

The effect of an electric field on the vibrational spectra, the Vibrational Stark Effect (VSE), has been utilized extensively to probe the local electric field in the active sites of enzymes [1, 2]. For this reason, the electric field and consequent polarization effects induced by a supramolecular host system upon its guest molecules attain special interest due to the implications for various biological processes. Although the host-guest chemistry of crown ether complexes and clathrates is of fundamental importance in supramolecular chemistry, many of these multicomponent systems have yet to be explored in detail using modern techniques [3]. In this direction, the electrostatic features associated with the host-guest interactions in the inclusion complexes of halogenated acetonitriles and formamide with 18-crown-6 host molecules have been analyzed in terms of their experimental charge density distribution. The charge density models provide estimates of the molecular dipole moment enhancements which correlate with the simulated values of dipole moments under electric field. The accurate electron density mapping using the multipole formalism also enable the estimation of the electric field experienced by the guest molecules. The electric field vectors thus obtained were utilized to estimate the vibrational stark effect in the nitrile (-C≡N) and carbonyl (C=O) stretching frequencies of the guest molecules via quantum chemical calculations in gas phase. The results of these calculations indicate remarkable elongation of C≡N and C=O bonds due to the electric fields. The electronic polarization in these covalent bonds induced by the field manifests as notable red shifts in their characteristic vibrational frequencies. These results derived from the charge densities are further supported by FT-IR experiments and thus establish the significance of a phenomenon that could be termed as the "supramolecular Stark effect" in crystal environment.

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Exploring the Effect of External Electric Field on Octane Dithiolate Molecular Nanowire: A Quantum Chemical and Charge Density Study

Journal of Computational and Theoretical Nanoscience ◽

10.1166/jctn.2013.2772 ◽

2013 ◽

Vol 10 (4) ◽

pp. 789-797 ◽

Cited By ~ 1

Author(s):

M. Jothi ◽

K. Selvaraju ◽

P. Kumaradhas

Keyword(s):

Electric Field ◽

Charge Density ◽

External Electric Field ◽

Quantum Chemical ◽

Density Study

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The electric field gradient at the position of copper in Cu2O and electronic charge density analysis by means of K-factors

Physics and Chemistry of Minerals ◽

10.1007/bf00309465 ◽

1983 ◽

Vol 9 (1) ◽

pp. 19-22 ◽

Cited By ~ 22

Author(s):

S. S. Hafner ◽

S. Nagel

Keyword(s):

Electric Field ◽

Electric Field Gradient ◽

Charge Density ◽

Field Gradient ◽

Electronic Charge ◽

Electronic Charge Density ◽

Density Analysis

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Conformational Flexibility and the Interaction of Huperzine A in the Active Site of Acetylcholinesterase: A Quantum Chemical and Charge Density Study

10.20944/preprints201608.0198.v1 ◽

2016 ◽

Author(s):

Renuga Parameswari Azhagesan ◽

Saravanan Kandasamy ◽

Kumaradhas Poomani

Keyword(s):

Molecular Docking ◽

Density Distribution ◽

Charge Density ◽

Gas Phase ◽

Active Site ◽

Quantum Chemical ◽

Conformational Flexibility ◽

Huperzine A ◽

Charge Density Distribution ◽

Density Analysis

Huperzine A is an herbal reversible inhibitor of Acetylcholinesterase (AChE). A molecular docking analysis on Huperzine A molecule has been carried out to understand its structure, conformational flexibility, intermolecular interaction and the binding affinity in the active site of AChE enzyme. Further, the charge density distribution of huperzine A molecule (lifted from the active site of AChE) was determined from the high level quantum chemical calculations coupled with charge density analysis. The binding affinity of Huperzine A towards AChE was calculated from the molecular docking; the lowest docked energy is -8.46 kcal/mol. In the active site, huperzine A molecule interacts with acyl binding pocket-Phe330 of AChE, that is, the bicyclo ring group of huperzine A forms an intermolecular interaction with the oxygen atom of main chain of the amino acid residue Phe330 at the distances 3.02 and 3.25 Å respectively. On the other hand, a gas phase study on huperzine A molecule also performed using HF and DFT (B3LYP) methods with the basis set 6-311G**. The molecular structure, conformation, and the charge density distribution of huperzine A molecule in the gas phase have determined using quantum chemical calculations and the charge density analysis. The comparative studies between the gas phase and the active site forms of huperzine A molecule, explicitly reveals the degree of conformational modification and the charge density redistribution of huperzine A when present in the active site. The dipole moment of the molecule in the active site is 6.85 D, which is slightly higher than its gas phase value (5.91 D). The electrostatic potential (ESP) surface of active site molecule clearly shows the strong electronegative and positive ESP regions of the molecule, which are the expected strong reactive locations of the molecule.

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