Bis-dithiano perylene diimide: synthesis and characterization of a novel ring system

We report the transformation of a 1,7-dibromo perylene diimide into a 1,6,7,12-tetrasulfur-substituted expanded ring system at room temperature in high yield. The resulting bis-dithiano perylene diimide completes the series of five sulfur-annulated perylene ring systems, the first four of which are known. We describe the synthesis and characterization of the title compound, PS4, and other sulfur-annulated species formed under slightly different conditions. Optical and electrochemical data of both solution and solid films of this compound are reported. At slow scan rate a film of PS4 self-organizes, rearranging its structure to accommodate its changing oxidation state. PS4 is a lightly n-doped semiconductor in inert atmosphere (conductivity, sigma = 4.6 x 10(-6) S cm(-1)) that becomes compensated in air (sigma = 2.4 x 10(-9) S cm(-1)) to an unusual, almost intrinsic (undoped) state. The properties of PS4 suggest applications in organic electronics.