Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The UV photoelectron spectra of isomeric para and meta derivatives of benzonitrile with substituents NO₂, COCH₃, Cl, Br, CH₂I and NH₂ were measured. Their assignment was carried out with the aid of MNDO calculations. The splitting of the highest π orbitals e_1gS, e_1gA is in all para derivatives greater than in their meta isomers, the greatest difference of splittings 0.25 eV being caused by the amino group. The level ordering e_1gS, A exists in all molecules except meta NO₂, and COCH₃ derivatives where it is believed to be reverse. The π'_CN - π_CN splitting keeps nearly constant and it is close to that in benzonitrile. The ionization potentials of σ orbitals e_1uS, e_1uA, b_2u and b_1u in meta NO₂ derivative are, in agreement with our expectation, higher than in benzonitrile. It is not true for para isomer where on the contrary, they are lower and they differ from meta isomer by 0.71-1.8 eV.