Characterization of New Rubrene Analogues with Heteroaryl Substituents

New
rubrene analogues, which are heteroaryl-tetrasubstituted tetracenes,
have been developed using a simplified synthesis approach. Their stabilities
in solution were improved compared to those of rubrene. The correlation
among the molecular structures, crystal structures, and charge transport
properties has been investigated and compared with rubrene and various
rubrene analogues. Although twisted structures of a tetracene backbone
have often been found in single crystal analyses, the planarity might
be related to intermolecular interactions rather than the electron
donating/withdrawing properties of the heteroaryl side groups. The
packing motifs in thiophene-substituted derivatives did not include π-stacking
of tetracene cores, which differ from the well-known structure of
rubrene. However, furan-substituted derivatives can be crystallized
in the π-stacking manner. These differences in the packing structure
affect hole transport properties.