Spectroscopic study of phthalic anhydride and its thia, selena, and tellura analogues

Abstract

The He(I) photoelectron, u.v.-visible absorption, 1H and 13C NMR, i.r. and Raman-laser spectra of selenophthalic and tellurophthalic anhydride have been obtained and compared to those of phthalic and thiophthalic anhydride. The main features of the spectra of these four compounds (the ordering and splitting of the n CO and π x ionizations, the location and nature of the π → π* transitions, the trend and spread of the chemical shifts, and the symmetry assignments of the fundamental vibrations) have been surveyed and discussed in terms of qualitative and correlative arguments, related to the ability of the chalcogen atoms to transmit electronic effects, and also with the aid of semi-empirical MO calculations. A fair correlation between the average ionization energy of the CO lone pair orbitals, the average of the CO stretching frequencies and the 13C carbonyl chemical shift has been found. The electric dipole moment, measured in benzene at 25°C, is 3.30D for selenophthalic anhydride and 2.71 D for tellurophthalic anhydride.