Novel nis(l,3-dithiole) donors ( 4) and ( 5) containing thiophene spacer units have been prepared.The cyclic voltammograms indicate that 4 and 5 are oxidized to mcation radicals and terracations, respectively, and on-site Coulombic repulsion in the dication state is reduced.An electroactive polymer was formed from 4c.The donors (4) and ( 5) gave conducting charge-transfer complexes with iodine.Recently much attention has been focused on the development of new electron donors which lead to organic conductors.'One of the recent trends involves the insertion of an extending and n-conjugating spacer group between two 1.3-dithiole units in order to decrease on-site Coulombic repulsion in the dication state and increase electron donating ability?Although there have been reported many such extended bis(l.3-dithiole)donors, molecules which possess more than three 1.3-dithiole moieties are little knowm3 Such molecules are expected to exhibit interesting electrochemical properties owing to the configuration as well as the number of 1,3-dithiole units.We have now prepared novel tris(l,3-dithiole) donors ( 4) and (5) containing thiophene units as spacer.The donors (4a-d) and (Sa-d) were synthesized by a Wittig-Horner reaction of the corresponding carbanions derived from phosphonate esters (3)4 with aldehyde (l)5 or ketone ( ~2 ) ~ in 27, 69,54,72,26,54,52, and 47% yields, respectively.The structures of new compounds were determined on the basis of the spectral data and elemental analyses.'TDedicated to Prof. Rolf Huisgen on the occasion of his 75th birthday.
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Yamashita et al. (1995) studied this question.