Scholl Reaction of Perylene‐Based Polyphenylene Precursors under Different Conditions: Formation of Hexagon or Octagon?
Ya Zou, Yi Han, Shaofei Wu, Xudong Hou, Chi Hao Eugene Chow, Jishan Wu
Abstract
Abstract A planar dibenzo‐peri‐hexacene derivative ( 2 ) was synthesized via FeCl 3 ‐mediated Scholl reaction from a cyclopenta‐fused perylene (CP) based polyphenylene precursor ( 1 ). However, an unexpected octagon‐containing, negatively curved molecule ( 3 ) was obtained in nearly quantitative yield when 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) and methanesulfonic acid (MeSO 3 H) were used. Similar results were observed when two smaller‐sized precursors containing one ( 4 ) or two CP units ( 5 ) were tested. X‐ray crystallographic analysis also revealed that there is no close π–π stacking between neighboring π‐conjugated skeletons. DFT calculations suggest a radical cation mechanism in the presence of FeCl 3 while an arenium ion pathway for the DDQ/MeSO 3 H mediated Scholl reaction, which can well explain the selective formation of hexagons and octagons under different conditions. The obtained compounds showed tunable optical and electrochemical properties.