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Geometry, solvent, and polar effects on the relationship between calculated core-electron binding energy shifts (Delta CEBE) and Hammett substituent (sigma) constants

TitleGeometry, solvent, and polar effects on the relationship between calculated core-electron binding energy shifts (Delta CEBE) and Hammett substituent (sigma) constants
Publication TypeJournal Article
Year of Publication2006
AuthorsSegala, M, Takahata, Y, Chong, DP
JournalJournal of Molecular Structure-Theochem
Volume758
Pagination61-69
Date PublishedJan
Type of ArticleArticle
ISBN Number0166-1280
Keywords25-DEGREES-C, ACCURATE, BENZENE-DERIVATIVES, benzenes, BENZOIC-ACIDS, CEBE shift, COMPILATION, DENSITY-FUNCTIONAL CALCULATION, DFF, Hammett sigma, IONIZATION, ISOLATED MOLECULES, LEAST-SQUARES, LFER, STRUCTURE-REACTIVITY PARAMETERS
Abstract

According to Lindberg et al. there exists an equation Delta CEBE=kappa sigma for substituted benzene derivatives. Core-electron binding energy shift (Delta CEBE) is the difference between the CEBE of a specific carbon in monosubstituted benzene derivatives (C6H5-Z) and in benzene (C6H5-H); K is related to a reaction constant and or is the experimental Hammett substituent constant. The object of the present work is to investigate geometry, solvent, and polar effects on Lindberg’s equation using theoretically calculated ACEBE. The CEBEs were calculated using DFT within the scheme Delta E-KS (PW86x-PW91c/TZP + C-rel). The geometry has only little effect on the CEBE values. A regression relation between ACEBE and 0, takes the form Delta CEBE = kappa sigma-C with K congruent to 1.17 and C congruent to 0.17. We estimated 69 sigma constants in water that have not been presented in the literature. Theoretical resonance (sigma(R)) and inductive (sigma(I)) effects were calculated using Taft equations. ACEBE (R) and ACEBE (1) effects on ACEBE were also calculated using Taft-like equations. The quality of the correlation to the resonance is better than that to the inductive effect, in water. The regression quality in aqueous organic solvent is poorer than in water in both Lindberg and Taft equations. The solvent effect is greater on the resonance than on the inductive effect. (c) 2006 Elsevier B.V. All rights reserved.

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