Tetramethyldithienothiophenes; new donors for cation radical salts

Three isomeric tetramethyldithienothiophenes, 2,3,2′,3′-tetramethyldithieno(5,4-b:4′,5′-d)thiophene 1, 2,3,2′,3′-tetramethyldithieno(4,5-b:5′,4′-d)thiophene 2, and 2,5,2′,5′-tetramethyldithieno(3,4-b:3′,4′-d)thiophene 3, have been synthesized. 2 and 3 show quasireversible cyclovoltammetric behaviour with halfwave potentials 0.92, and 0.95 V vs SCE respectively. Two new cation radical salts, (2)2PF6 and (2)2PF6, have also been isolated.