Spectroscopic and theoretical determination of the electronic structure of anisole, 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 para- and ortho-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 determined experimentally. The assignments of the spectra, based on those of the parent compounds PhXMe, NCPh, and XMe2 (Me = CH3), agree with the results of theoretical HF/6-31G** calculations. The calculations correctly reproduce the prevalence of the planar rotamer of the oxy-derivatives with respect to the gauche one, while overestimating the relative stability of the gauche conformer of the thio-derivatives. The two rotamers of the thio-derivatives have similar energy and their valence energy levels do not sizeably differ. In addition, PhSMe and p-NCPhSMe have HOMO-LUMO energy gaps (9.5 eV) in the oxy-derivatives and there are indications that the methylthio group has larger polarizability than the methoxy group. These data suggest that poly(p-phenylene sulfide) is more suitable than poly(p-phenylene oxide) to carry electricity under mild doping