Steric inhibition of resonance studied by molecular photoelectron spectroscopy. Part 1.—Biphenyls

Abstract

The helium I photoelectron spectroscopy of 30 biphenyls is reported. An empirical correlation between certain bands in the spectra and dihedral angle is noted and its use in conformational studies emphasized. An interpretation of the higher energy bands is given in terms of a Hückel-type theory based on the interaction between semi-localized π molecular orbitals. Substituent effects are divided into electronic and steric and means for separating these two factors are outlined.