Electronic characteristics of large π-electron conjugated dumbbell-shaped donors and their radial cationic salts

We investigated the new concept of donors in the synthesis of organic metals. We studied two dumbbell-shaped donors, 1,4-bis[2-(1-pyrenyl)ethenyl]-2,5-dimethylbenzene (BPE-DMB), and 1,4-bis[2-(1-pyrenyl)ethenyl]benzene (BPE-B) and found that they have good solubility in spite of extended π-electron conjugation. These donors were easily formed into highly conductive salts; for example, dibromoiodide (IBr2) salts had conductivities as high as 100 S/cm at room temperature. Above 220 K, the (BPE-DMB)(IBr2) salt showed metallic conducting behavior. We used the electron resonance spectra and the reflectance spectra of these salts to examine to be metal or not around these temperature. Furthermore, infrared spectra showed that the π-electron conjugation of BPE-DMB extended over the entire molecule in the salt. Therefore, it was appeared that the (BPE-DMB)(IBr2) salt was novel one which exhibited a metal state in spite of the donor being in a mono-cationic state.