Molecular complexes of substituted thiophens with σ and π acceptors. Charge transfer spectra and ionization potentials of the donors

Abstract

Charge transfer complexes of substituted thiophens as donors with tetracyanothylene, 2,3-dichloro-5,6-dicyano-p-benzoquinone, chloranil and iodine have been studied spectrophotometrically. From the energies of the charge transfer transitions, the ionization potentials of the donors have been obtained. Comparison with those measured by electron-impact mass spectrometry, shows that the thiophens behave as π donors with all four acceptors. In the case of iodine the stability constants of the complexes support a π→σ^* interaction. Some evidence is given for the role of inner valence orbitals in the complexes.