Synthesis and thermoelectric properties of 2- and 2,8-substituted tetrathiotetracenes

Abstract

Thermoelectric properties (conductivity and Seebeck coefficient) are in screening for new tetrathiotetracene lead materials. Iodine doping reveals iPr,Me-TTT as optimal.

Capturing Waste Heat Energy with Charge-Transfer Organic Thermoelectrics

“…19 An overview of known syntheses of unsubstituted and substituted TTT has recently been collected and this also demonstrates these literature accessibility issues. 20 Evaluating the known experimental details, supplemented by our own experiences in this area, it is justified to suggest the direct reaction of tetracene (2), or one of its derivatives, with sulfur in refluxing DMF is the most appropriate method for the synthesis of TTTs. This path (A) was first outlined by Perez-Alberne (Scheme 2) as long ago as 1973.…”

“…21 Given the wider availability of various tetracenes (at similar cost), the method of choice, in our opinion, is pathway A which typically offers good yields and simple work-ups. 20 For example, reaction of the parent tetracene (2) and elemental sulfur in DMF afforded, after refluxing the mixture (4-5 h) and hot filtration, the desired TTT (1) in crude yields above 95%. For purification, a simple Soxhlet extraction with toluene and/or CS 2 is effective in removing sulfur impurities and a by-product identified as dithiotetracene.…”