ELECTRONIC-STRUCTURE OF ETHYNYLTHIOPHENES

He I and He II photoelectron spectra of all isomeric mono- and diethyn ylthiophenes were recorded. The electronic structure was analyzed and spectra assigned on the basis of empirical considerations and semiempi rical MO calculations. The spectra indicate various interactions takin g place between thiophene pi and ethynyl pi orbitals. The relationship between deduced electronic structure and formation of novel polymer m aterials is discussed.