SINGLE-COMPONENT DONOR-ACCEPTOR ORGANIC SEMICONDUCTORS DERIVED FROM TCNQ

o[b]naphtho[2,3-e][1,4]dithiin-6,11-quinodimethane (9a) and 13,13,14,1 4-tetracyanobenzo[b]naphtho[2,3-e] [1,4]oxathiin-6,11-quinodimethane ( 10a) and their methyl-substituted derivatives(9b and 10b-d, respective ly) have been prepared as single-component donor-acceptor compounds fr om the corresponding quinones 7 and 8 by using the Lehnert's reagent. UV-vis spectra of the novel compounds reveal the presence of an intram olecular electronic transfer from the donor to the acceptor moiety. Cy clic voltammetry displays, in addition to the oxidation peak, a two-el ectron reduction wave to the dianion, as confirmed by controlled poten tial coulometry analysis. The crystallographical study carried out on single crystals of compound 10d shows that molecules are not planar an d stack with aromatic interactions between donor and acceptor moieties . In agreement with the crystallographical results, the electrical con ductivity measured on a powder sample of 10c exhibits semiconductive b ehavior. Molecular orbital calculations using the PM3 semiempirical me thod were performed on both neutral and oxidized/reduced compounds and predict that molecules are severely distorted from planarity. Distort ions are compared with crystallographic data and are analyzed in terms of nonbonding interactions and crystal packing. Valence effective Ham iltonian (VEH) nonempirical calculations were used to study the electr onic properties and support the intramolecular charge-transfer nature of the lowest-energy absorption band. The evolution of the geometric s tructure evidences a gain of aromaticity upon oxidation and reduction that just the obtention of stable cations and,anions. The observation of a unique two-electron reduction wave to the dianion is rationalize; by comparing the electronic and structural changes induced by reductio n on compound 9a and on the parent TCNQ molecule.