Gas Phase UPS Investigation of Trans-Azobenzenes

Abstract

Abstract The first two ionization energy values of p-substituted trans-azobenzenes pX-C6H4-N = N-C6H5 (X = NH2, OCH3, OH, CH3, H, Cl, COOH and NO2) are reported. These have been obtained by U.V. (HeI and HeII) photoelectron spectroscopy (UPS). The substituent effect indicates that for electron donor substituents, the highest occupied orbital is π-type. This is confirmed by semiempirical calculations. When the substituent is H or a withdrawing group, the first two bands heavily overlap, and in these cases no certain assignment was possible, in spite of the several approaches used. The UPS data are discussed along with previous polarographic and U.V. absorption measurements.