Synthesis of symmetrical and asymmetrical singly bridged bis-TTFs containing sulfur and selenium atoms. A study of some of their radical cation salts

Abstract

By using a chalcogenolate (thiolate or selenolate) protection–deprotection strategy, a series of singly bridged bis-TTFs, 3a–c, 4a, have been prepared in high yield (84–96%) through two different routes. Route 2, involving the reaction between a monochalcogenolate TTF derivative with a previously prepared monoiodinated TTF species, appears to be a very useful and general strategy to selectively prepare bis-TTFs in high yields (84–90%). The bis-TTFs, 3a–c, 4a, are easily converted into the corresponding dimethylated derivatives 3a′–c′, 4a′ in a basic (2 equiv.) IMe medium. The electron-donating ability of this series of bis-TTFs has been determined by cyclic voltammetry. Several salts, mainly perchlorates, of the donors 3a, 4a, 3a′–c′ have been obtained as black powders by galvanic electrosynthesis. Their room temperature electrical conductivity as compressed powder pellets has been measured, together with the temperature dependence of the ESR signal.