Synthesis and properties of a twin donor molecule composed of cofacially stacked dihydrodiazapentacenes

A clip-shaped donor–acceptor–donor (D–A–D) molecule (1) has been prepared with 6,13-dihydro-6,13-diazapentacene (DHDAP) as a building unit. X-Ray single crystal analysis revealed the structure of 1 whose DHDAP moieties confront each other in close proximity. The electrochemical measurements showed that this molecule could be oxidized up to the tetracation reflecting its twin donor structure with two DHDAP units. Spectroscopic measurements (UV/vis-NIR, ESR) of 1˙+ suggested the full delocalization of the radical spin over the two DHDAP units. The stable radical cation salt 1˙+·[SbF6]− was obtained by chemical oxidation of 1. The packing structure of 1˙+·[SbF6]− was a kind of segregated stacking, which is desirable for charge conduction. Actually, photoconductivity measurement by the microwave technique revealed that 1˙+·[SbF6]− has more than 10 times higher photoconductivity than its neutral state with an extraordinary long lifetime of charge separated states, suggesting its feasibility as light-energy harvesting cores even in the near-IR region.