On the application of a modified Sanderson formalism to atomic charge-C 1s binding energy correlation in some aromatic molecules

The modified Sanderson formalism for calculation of atomic charge in organic molecules has been shown to yield good correlation with core level binding energy (BE) shifts in organic molecules where final state relaxation effects can be neglected. Based on the concept of stability ratios, which is similar to electronegativity, this approach has the advantage of being intuitive in addition to being computationally non-intensive. However, in aromatic molecules where delocalized π electrons can contribute significantly to final-state relaxation energies, no attempt has been made to study whether such a correlation is feasible. In this communication, we seek to study the correlation between the C 1s binding energy (BE) in some aromatic organic molecules and the atomic charge on the carbons determined using the modified Sanderson method. A linear regression curve is found to fit the data satisfactorily with the degree of fit being better than for charges calculated by the MNDO quantum chemical method. There is, however, a difference in the regression curves for aromatic molecules and molecules with carbon in the sp³-hybridized state (Sastry, J. Electron Spectrosc., in press). If the discrepancy is attributed to final-state core hole relaxation effects, calculated relaxation energies are found to be unphysical. This aspect notwithstanding, the quality of the regression found for aromatic molecules suggests that the modified Sanderson formalism can be applied to aromatic molecules with some care.