Higher-spin pi multiradical sites in doped polyarylamine polymers

Abstract

P-Doping of conjugated polymers based on an extended m-phenylenediamine motif produces a disperse population of ferromagnetically coupled spin clusters. To increase the average size of these spin clusters variations have been explored both in the structure of the polymer and in the method of doping. Introduction of ferromagnetic spin coupling ‘2,7 through the naphthalene nucleus’ rather than ‘1,3 through the benzene nucleus’ has been investigated as have variations in the aryl core/alkyl side chain ratio but the biggest improvements were achieved by adopting a doping procedure in which thin films of the polymer were exposed to gaseous antimony pentachloride. A thin film (ca. 1 µm thick) of the polymer obtained by the Pd⁰-mediated coupling of 1,3-dibromo-5-tetradecylbenzene with tris[2-butoxy-4-(dihydroxyboranyl)phenyl]amine was exposed to gaseous antimony pentachloride. Under these conditions 40–60% of the potentially dopable sites were oxidised to the amminium ion (N^˙+) level. A Brillouin function fit to the field dependence of the magnetisation of this doped polymer at 2 K corresponds to behaviour equivalent to a nonet (S = 4) pi multiradical.