CONFORMATIONAL ANALYSIS OF TERPHENYLS BY PHOTOELECTRON SPECTROSCOPY.

Abstract

Vapor phase HeI photoelectron spectra of o- and m-terphenyl were measured, and conformational analysis of biphenyl, o-, m-, and p-terphenyl was made by comparing the observed photoelectron spectral patterns with the calculated ones by the CNDO/S method, the inter-ring twist angles in these compounds being estimated to be around 40 degree , 60 degree , 40 degree , and 40 degree , respectively. The results that the inter-ring twist angles in o-terphenyl are far smaller than 90 degree is completely in contrast to the long believed perpendicular model of o-terphenyl suggested by the gas electron diffraction study.