Relationship between calculated core‐electron binding energy shifts and Hammett substituent (sigma) constants: I

For monosubstituted benzenes (Ph‐Z), Linderberg et al. demonstrated the validity of the equation ΔCEBE ≈ κσ, where ΔCEBE is the difference between the core‐electron binding energies (CEBE) of a specific carbon in monosubstituted benzene derivatives (Ph‐Z) and that of unsubstituted benzene (Ph‐H), κ is related to the reaction constant and σ is the experimental Hammett sigma constant. CEBEs of carbon atoms for a series of Ph‐Z were calculated using density functional theory (DFT) with the scheme Δ E KS (PW86‐PW91)/TZP+ C rel //HF/6‐31G*. An average absolute deviation of 0.15 eV was obtained with respect to observed values. A linear regression analysis of the form Y  =  A + BX of a plot of, for instance, Hammett σ p ‐constants against calculated ΔCEBEs (in eV) at para ‐carbon for n  = 11 produced a value of A  = −0.1310 and B  = 1.056 with a correlation coefficient R  = 0.983, a standard deviation of 0.099 and a p ‐value  < 0.0001. Copyright © 2004 John Wiley & Sons, Ltd.