Highly Conducting and Flexible Radical Crystals

Together with high conductivity, high flexibility is an important property required for next generation organic electronic components. Both properties are difficult to achieve together especially when the components are crystalline because of the intrinsic high brittleness of organic molecular crystals. We report an organic radical crystal system that has both high flexibility and high conductivity. The crystal consists of 9,10-bis(phenylethynyl)anthracene radical cation (BPEA^.+ ) units, and shows flexibility under pressure with high conductivity in ambient condition exhibiting average conductivity of 2.68 S cm^-1 when normal linear shape, as well as 2.43 S cm^-1 when bent. The structural analysis reveals that both a short π-π distance (3.290 Å) between BPEA^.+ units that are aligned along the crystal length direction, and the presence of PF₆ ^- counter ions induce flexibility and high electrical conductivity.