Novel Bis (1,3-Dithiole) Electron Donors by Oxidative Intramolecular Cyclization of 2,2′-Bis(1,4-Dithiafulven-6-yl)-3,3′-Bithienyls

Abstract

2,2′-Bis(1,4-dithiafulven-6-yl)-3,3′-bithienyls 6 were prepared by using either a Wittig or a Wittig-Homer reaction. The cyclic voltammograms of 6 revealed that they undergo an intramolecular cyclization by electrochemical oxidation. Chemical oxidation of 6 with tris(4-bromophenyl)aminium hexachloroantimonate gave intramolecular cyclization products 16 as dication salts. The hexachloroantimonate ion was found to act as an oxidizing agent in the reaction. Chemical reduction of the dication salts with zinc afforded the corresponding neutral bis (1,3-dithiole) donors 7 in high yields. The cyclic voltammograms of 7 showed reversible one-stage two-electron oxidation waves, and the potentials are fairly low. A conductive TCNQ complex was formed from one of them. X-ray analyses of the neutral and dication states of the donor show that there is a large conformational change between them.