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Conformational Dependence of sigma-E...

Jovanovic, Milena.

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Conformational Dependence of sigma-Electron Delocalization in the Catenae XnMe2n+2, X = Si, Ge, Sn, and Pb.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Conformational Dependence of sigma-Electron Delocalization in the Catenae XnMe2n+2, X = Si, Ge, Sn, and Pb./
Author:	Jovanovic, Milena.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
Description:	528 p.
Notes:	Source: Dissertation Abstracts International, Volume: 80-09(E), Section: B.
Contained By:	Dissertation Abstracts International80-09B(E).
Subject:	Chemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13858215
ISBN:	9781392165065

Conformational Dependence of sigma-Electron Delocalization in the Catenae XnMe2n+2, X = Si, Ge, Sn, and Pb.
Jovanovic, Milena.

Conformational Dependence of sigma-Electron Delocalization in the Catenae XnMe2n+2, X = Si, Ge, Sn, and Pb. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 528 p.

Source: Dissertation Abstracts International, Volume: 80-09(E), Section: B.

Thesis (Ph.D.)--University of Colorado at Boulder, 2019.

Bonds of sigma type are the most common chemical bonds, dominating bonding in all molecules and defining the framework of a molecule. It has been long known that electrons in sigma bonds can delocalize throughout a molecule. However, the nature of sigma-electron delocalization is not fully understood due to its complexity. One of the important aspects of sigma-electron delocalization is its conformational dependence, first noted in oligosilanes where properties of a molecule change drastically when it changes conformation. This dissertation describes efforts to understand the conformational dependence of sigma delocalization in oligosilanes and their heavier analogs using simple intuitive models and density functional theory (DFT) calculations. The first part of the dissertation focuses on studying the conformational dependence of electron delocalization in oligosilanes. It is shown that oligosilanes can exist as two distinct chromophores, sigma-delocalized conformers with large dihedral angles and sigma-localized conformers with small dihedral angles. Properties of a conformer are dictated by the shape of frontier molecular orbitals, which is different for conformers with small and large dihedral angles. The origin of the conformational dependence is found in the interplay between two delocalization mechanisms, which can lead to enhancement of delocalization or to its complete annihilation. The second part of the dissertation describes characteristics of sigma-electron delocalization in linear infinite polysilane, polygermane, polystannane, and polyplumbane. The conformational dependence of electron delocalization is confirmed in all these molecules. Effective hole mass is used to indicate an extent of the delocalization, while a position of the Fermi level in reciprocal space is used to determine the dominant mechanism of delocalization. The simple model used to explain the origin of the conformational dependence of electron delocalization in saturated compounds is verified by comparison with density functional theory calculations. Relatively simple analysis presented here provides an important insight into properties of a complex ubiquitous phenomenon of delocalization of electrons through sigma bonds.

ISBN: 9781392165065Subjects--Topical Terms:

516420
Chemistry.

Conformational Dependence of sigma-Electron Delocalization in the Catenae XnMe2n+2, X = Si, Ge, Sn, and Pb.
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500 $a Source: Dissertation Abstracts International, Volume: 80-09(E), Section: B.
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520 $a Bonds of sigma type are the most common chemical bonds, dominating bonding in all molecules and defining the framework of a molecule. It has been long known that electrons in sigma bonds can delocalize throughout a molecule. However, the nature of sigma-electron delocalization is not fully understood due to its complexity. One of the important aspects of sigma-electron delocalization is its conformational dependence, first noted in oligosilanes where properties of a molecule change drastically when it changes conformation. This dissertation describes efforts to understand the conformational dependence of sigma delocalization in oligosilanes and their heavier analogs using simple intuitive models and density functional theory (DFT) calculations. The first part of the dissertation focuses on studying the conformational dependence of electron delocalization in oligosilanes. It is shown that oligosilanes can exist as two distinct chromophores, sigma-delocalized conformers with large dihedral angles and sigma-localized conformers with small dihedral angles. Properties of a conformer are dictated by the shape of frontier molecular orbitals, which is different for conformers with small and large dihedral angles. The origin of the conformational dependence is found in the interplay between two delocalization mechanisms, which can lead to enhancement of delocalization or to its complete annihilation. The second part of the dissertation describes characteristics of sigma-electron delocalization in linear infinite polysilane, polygermane, polystannane, and polyplumbane. The conformational dependence of electron delocalization is confirmed in all these molecules. Effective hole mass is used to indicate an extent of the delocalization, while a position of the Fermi level in reciprocal space is used to determine the dominant mechanism of delocalization. The simple model used to explain the origin of the conformational dependence of electron delocalization in saturated compounds is verified by comparison with density functional theory calculations. Relatively simple analysis presented here provides an important insight into properties of a complex ubiquitous phenomenon of delocalization of electrons through sigma bonds.
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