Since the first synthesis of dibenzopentalene 1 by Brand in 1912,[1a] pentalene derivatives have had a long history of studies on their synthesis, structures, and electronic properties.[1, 2] Recently, polycyclic conjugated systems bearing carbocyclic five-membered rings such as fluorenes [3] and indenes [4] have attracted much attention because of their utility in organic electronic devices. However, the application of pentalene derivatives to organic ...
