Information theory insights into molecular electronic structure and reactivity

doi:10.1007/978-3-642-32753-7_2

Information theory insights into molecular electronic structure and reactivity

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Information theory insights into molecular electronic structure and reactivity

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punktacja MNiSW [2012 A]: 40

title:	Information theory insights into molecular electronic structure and reactivity
author:	Nalewajski Roman
editor:	Mingos D. Michael P., Putz Mihai V.
book title:	Applications of density functional theory to chemical reactivity
date of publication :	2012
place of publication : name of publisher:	Berlin : Springer
pages:	51-93
ISBN:	978-3-642-32752-0
eISBN:	978-3-642-32753-7
series:	Structure and Bonding, ISSN 0081-5993, eISSN 1616-8550; 149
DOI:	10.1007/978-3-642-32753-7_2
language:	English
book language:	English
abstract in English:	Struct Bond (2012) 149: 51–94 DOI: 10.1007/978-3-642-32753-7_2 # Springer-Verlag Berlin Heidelberg 2012 Information Theory Insights into Molecular Electronic Structure and Reactivity Roman F. Nalewajski Abstract Selected concepts and techniques of Information-Theory (IT) are summarized and their use in probing the molecular electronic structure is advocated. The electron redistributions accompanying formation of chemical bonds, relative to the (molecularly placed) free atoms of the corresponding “promolecule,” generate the associated displacements in alternative measures of the amount of information carried by electrons. The latter are shown to provide sensitive probes of information origins of the chemical bonds, allow the spatial localization of bonding regions in molecules, and generate attractive entropy/ information descriptors of the system bond multiplicities. Information-theoretic descriptors of both the molecule as a whole and its diatomic fragments can be extracted. Displacements in the molecular Shannon entropy and entropy deficiency, relative to the promolecular reference, are investigated. Their densities provide efficient tools for detecting the presence of the direct chemical bonds and for monitoring the promotion/hybridization changes the bonded atoms undergo in a molecular environment. The nonadditive Fisher information density in the Atomic Orbital (AO) resolution is shown to generate an efficient Contra-Gradience (CG) probe for locating the bonding regions in molecules. Rudiments of the Orbital Communication Theory (OCT) of the chemical bond are introduced. In this approach molecules are treated as information systems propagating “signals” of electron allocations to basis functions, from AO “inputs” to AO “outputs.” The conditional probabilities defining such an information network are generated using the bond-projected superposition principle of quantum mechanics. They are pro- portional to squares of the corresponding elements of the first-order density matrix in AO representation. Therefore, they are related to Wiberg’s quadratic index of the chemical bond multiplicity. Such information propagation in molecules exhibits typical communication “noise” due to the electron delocalization via the system chemical bonds. In describing this scattering of electron probabilities throughout the network of chemical bonds, due to the system occupied Molecular Orbitals (MO), the OCT uses the standard entropy/information descriptors of communica- tion devices. They include the average communication noise (IT covalency) and information flow (IT ionicity) quantities, reflected by the channel conditional entropy and mutual information characteristics, respectively. Recent examples of applying these novel tools in an exploration of the electronic structure and bonding patterns of representative molecules are summarized. This communication perspec- tive also predicts the “indirect” (through- bridge ) sources of chemical interactions, due to the “cascade” probability propagation realized via AO intermediates. It supplements the familiar through- space mechanism, due to the constructive interference between the interacting AO, which generates the “direct” communi- cations between bonded atoms. Such bridge “bonds” effectively extend the range of chemical interactions in molecular systems. Representative examples of the p systems in benzene and butadiene are discussed in a more detail and recent applications of the information concepts in exploring the elementary reaction mechanisms are mentioned.
keywords in English:	Bond information probes, Direct/indirect bond multiplicitie, Bond localization, Entropic bond indices, Chemical bonds, Fisher informatio, Chemical reactivity, Information theory, Contra-gradience criterion, Molecular information channels, Covalent/ionic bond components, Orbital communications
number of pulisher's sheets:	2,86
affiliation:	Wydział Chemii : Zakład Chemii Teoretycznej im. K. Gumińskiego
type:	chapter
subtype:	academic paper

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