X-Ray Photoelectron Spectra of σ Complexes of 1, 3, 5-Trinitrobenzene and Picric Acid

Abstract

Photoelectron spectra of sodium and/or piperidine salts of six kinds of σ complexes obtained from either 1, 3, 5-trinitrobenzene or picric acid were measured. The results showed that binding energies of 1 s electrons of nitrogen atoms of a complex differ distinctly from each other, but those of oxygen atoms differ slightly and those of carbon atoms are approximately equal. The difference of binding energies of nitrogen atoms of three nitro groups was attributed to the different degree of polarization of these groups in a crystalline form. Charge densities of nitrogen atoms of all σ complexes measured were estimated from the correlation curve established between binding energies of nitrogen atoms of several compounds and their charge densities calculated by the CNDO/2 method. Disagreement was noted in charge densities of complex II calculated by the CNDO/2 method and that estimated by the present method.