SINGLE-COMPONENT DONOR-ACCEPTOR ORGANIC SEMICONDUCTORS DERIVED FROM TCNQ

13,13,14,14-Tetracyanobenzo[b]naphtho[2,3-e][1,4]dithiin-6,11-quinodimethane (9a) and 13,13,14,14-tetracyanobenzo[b]naphtho[2,3-e] [1,4]oxathiin-6,11-quinodimethane (10a) and their methyl-substituted derivatives(9b and 10b-d, respectively) have been prepared as single-component donor-acceptor compounds from the corresponding quinones 7 and 8 by using the Lehnert's reagent. UV-vis spectra of the novel compounds reveal the presence of an intramolecular electronic transfer from the donor to the acceptor moiety. Cyclic voltammetry displays, in addition to the oxidation peak, a two-electron reduction wave to the dianion, as confirmed by controlled potential coulometry analysis. The crystallographical study carried out on single crystals of compound 10d shows that molecules are not planar and stack with aromatic interactions between donor and acceptor moieties. In agreement with the crystallographical results, the electrical conductivity measured on a powder sample of 10c exhibits semiconductive behavior. Molecular orbital calculations using the PM3 semiempirical method were performed on both neutral and oxidized/reduced compounds and predict that molecules are severely distorted from planarity. Distortions are compared with crystallographic data and are analyzed in terms of nonbonding interactions and crystal packing. Valence effective Hamiltonian (VEH) nonempirical calculations were used to study the electronic properties and support the intramolecular charge-transfer nature of the lowest-energy absorption band. The evolution of the geometric structure 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 reduction on compound 9a and on the parent TCNQ molecule.