The switching properties of a polyene containing up to 10 carbons and substituted by organic donor- (D) and acceptor- (A) type molecules have been theoretically investigated. N,N-dimethylaniline and nitrobenzene were taken as D and A substituents, respectively, and are linked to the central carbon atoms of the polyene. The molecular geometry has been fully optimized within the well known AM1 technique. Calculations have been carried out for the ground state, first excited state, singly positive and negative ions, and for the neutral system under the influence of a static electric field. Ground and first excited states present carbon rings of both lateral groups nearly perpendicular to the polyene chain and the excited state does not correspond to an electron transferred from D to A. In the molecular ions, the extra charge concentrates mostly on the polymer chain, with smaller contributions on the appropriate lateral group. The effects of a static electric field applied along the substituents have been considered. It is found that, for the field pointing to D, a charge transfer may occur if there is a double bond between the carbons to which the ligands are bonded. As a consequence, conjugation is interrupted on the polyene. No important modifications occur on the system's geometry when the field points to A nor when the substituents are bonded around a single bond in the polyene. These results are consistent with Carter's prediction of a soliton switch. © 1992.511-3179186Proc. Int. Conf. Science Technology of Synthetic Metals, ICSM' 1990 (1991) Synth. Met., 41-43. , See, for exampleBaumann, Manring, Easton, (1988) Molecular Electronic Devices, p. 123. , F.L. Carter, R.E. Siatkowski, H. Wohltjen, Elsevier/North-Holland, AmsterdamCarter, (1982) Molecular Electronic Devices, , Marcel Dekker, New YorkSu, Schrieffer, Heeger, (1980) Phys. Rev. B, 22, p. 2099Tanaka, Yamanaka, Koike, Yamabe, (1985) Phys. Rev. B, 32, p. 2731Spangler, McKoy, (1988) Molecular Electronic Devices, p. 609. , F.L. Carter, R.E. Siatkowski, H. Wohltjen, Elsevier/North-Holland, AmsterdamDewar, Zoebisch, Healy, Stewart, (1985) J. Am. Chem. Soc., 107, p. 4433Longo, (1988) MSc. ThesisChance, Boudreaux, Brédas, Silbey, (1983) Phys. Rev. B, 27, p. 1440André, Brédas, Delhalle, Vanderveken, Vercauteren, Fripiat, (1990) Modern Techniques in Computational Chemistry: MOTECC 90, p. 745. , VEH:, E. Clementi, ESCOM, LeidenM. C. dos Santos, unpublishedFerray, Lompré, Gobert, L'Huillier, Maintray, Manus, Sanchez, Gomes, (1990) Optics Commun., 75, p. 278