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

 Title Geometry, solvent, and polar effects on the relationship between calculated core-electron binding energy shifts (Delta CEBE) and Hammett substituent (sigma) constants Publication Type Journal Article Year of Publication 2006 Authors Segala, M, Takahata, Y, Chong, DP Journal Journal of Molecular Structure-Theochem Volume 758 Pagination 61-69 Date Published Jan Type of Article Article ISBN Number 0166-1280 Keywords 25-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. URL ://000235255700009
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