The filled and empty level structures of the thiazyl chains R-NSN-R and (R-NSN)(2)S, with R = Si(CH3)(3), are investigated by means of ultraviolet photoelectron and electron transmission spectroscopy. The spectral features are interpreted with the support of ab initio Hartree-Fock (HF)/6-31G* and semiempirical AM1 calculations. within the Koopmans' theorem approximation, and with density functional theory. using the orbital energies of the transition state electronic configuration. Post-HF calculations with infinite-order coupled-cluster expansion are employed to evaluate the first vertical electron affinity value of R-NSN-R, with R = H and CH3. The experimental and theoretical results obtained for the thiazyl chains, as well as those for trans-oligoethenes, are extrapolated in order to evaluate the first ionization energy and electron affinity values for the corresponding (ideal) gas-phase polymers. Poly(sulfur nitride) is predicted to possess a smaller ionization energy and a sizeably higher electron affinity than those of trans-polyacetylene, with a consequent greatly reduced highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap, in agreement with its highly conductive nature.