Spectroscopic and theoretical determination of the electronic structure ofanisole, thioanisole, and methoxy- and methylthiobenzonitriles: A contribution to the study of organic conducting polymers

Gas-phase ionization and attachment energy (IE and AE) values of some p- an d o-cyano derivatives of anisole and thioanisole (p-NCPhXCH3, X = O, S; and o-NCPhXR, X = O, R = CH3; X = S, R = H, CH3, and C(CH3)(3)) have been dete rmined experimentally. The assignments of the spectra, based on those of th e parent compounds PhXMe, NCPh, and XMe2 (Me = CH3), agree with the results of theoretical HF/6-31G** calculations. The calculations correctly reprodu ce the prevalence of the planar rotamer of the oxy derivatives with respect to the gauche one, while overestimating the relative stability of the gauc he conformer of the thio derivatives. The two rotamers of the thio derivati ves have similar energy and their valence energy levels do not sizably diff er. In addition, PhSMe and p-NCPhSMe have HOMO-LUMO energy gaps (<9.0 eV) s maller than the corresponding value (>9.5 eV) in the oxy derivatives and th ere are indications that the methylthio group has larger polarizability tha n the methoxy group. These data suggest that poly(p-phenylene sulfide) is m ore suitable than poly(p-phenylene oxide) to carry electricity under mild d oping.