Electronic structure of pentatomic heterocyclic compounds containing N, O, S, and Se. Gas-phase Uv photoelectron spectra and quantum-mechanical calculations.

The gas-phase UV photoelectron spectra of a series of pentatomic heterocyclic molecules having the hydantoin skeleton, i.e. {A figure is presented} are discussed on the ground of comparison with the spectra of analogous molecules and with the results of HAM 3 and/or CNDO/S calculations. Evidence was found of the presence of significant interactions between the π orbitals of the chalcogen atoms when X and Y were sulfur and/or selenium. The π orbitals of the nitrogen atoms are on the contrary pretty much localised in the whole series, particularly when X=Y=O and in the monosubstituted derivatives