Oligomers from biphenyl, biphenyl‐d10, or p‐terphenyl with aluminium chloride‐cupric chloride: Mechanism, ESR, and conductivity

Biphenyl and biphenyl‐d10 were coupled by aluminum chloride‐cupric chloride. For the two systems, the yields of p‐quaterphenyl, p‐sexiphenyl, and sublimation residue were compared. The results, which have mechanistic significance, are similar to those reported earlier for benzene versus benzene‐d6; that is, a decrease in DP for the deuterated substrate. p‐Sexiphenyl, obtained from biphenyl or p‐terphenyl and aluminum chloride‐cupric chloride, displayed a concentration of 3 × 1017 spins/g in ESR. There was little or no change in spin density after sublimation or crystallization. Even after drastic purification by a variety of techniques the radical character persisted. Biphenyl was polymerized by aluminum chloride‐cupric chloride at temperatures in the 50–155°C range. Processable polymers with m‐ and p‐phenylene linkages were produced. When doped with AsF5, the highest conductivity obtained was 7.3 × 10−2 Ω−1 cm−1.