The Tetrathioporphycene Redox System: Electrochemical Reduction of a 20? Cyclophane to Its Diatropic 22? Dianion

Article abstract of DOI:10.1007/BF00816416

The reductive carbonyl coupling (McMurry reaction) of 5,5'-diformyl-2,2'-bithiophene affords the fourfold sulfur bridged <20>annulene 5 and its <30>annulene homologue 10 in 8 and 3percent yields.Coupling of 5,5''-diformyl-2,2':5',2''-terthiophene produces structurally related macrocycles, albeit in very low yields.As shown by X-ray crystallographic investigation, the bridged annulenes 5 and 10 are non-planar cyclophanes exhibiting transannular electronic interaction.The sulfur bridged <20>annulene 5 constitutes the central molecule of the tetrathiaporphycene redox system emcompassing the dicationic tetrathiaporphycene 3, the annulene 5, the 22? dianion 8 and the two intermediate radical ion species.Compound 5 is reduced in one two-electron step giving the diatropic 22-? dianion 8 which is characterized by cyclovoltammetry, coulometry, spectroelectrochemistry and 1H-NMR spectroscopy.By contrast, 5 fails to undergo oxidation with formation of the dicationic 18? tetrathioporphycene. - Keywords.McMurry reaction; 1H-NMR; Crystal structure; Voltammetry; Coulometry; Spectroelectrochemistry.