STRUCTURAL AND ELECTRONIC-PROPERTIES OF OLIGOMERIC HETEROARYLENE VINYLENES - A THEORETICAL APPROACH

The structural and electronic properties of trans-bis (2-thienyl)ethyl ene, trans-bis(2-furyl)ethylene and trans-bis(2-pyrryl) ethylene have been investigated from a theoretical standpoint. Ab initio methods hav e been employed to calculate the geometric structures and ionization p otentials. Furthermore, VEH ionization potentials and pi-pi electroni c transitions are reported. A progressive decrease of the ionization p otential occurs when exchanging sulfur by oxygen and when replacing ox ygen by a NH group. An increase of the energy of the first electronic transition is observed in going from trans-bis(2-thienyl)ethylene to t rans-bis(2-furyl)ethylene but not when passing to trans-bis(2-pyrryl)e thylene. These trends are correlated with available theoretical and ex perimental data on polymers. The adequacy of ab initio and VEH methods to predict correctly the electronic properties of trans-bis(2-furyl)e thylene is discussed.