p-Doped high spin polymers1

Abstract

High spin polymers have been created from p-doping of networked polyaryl and polyarylamine polymers which were synthesized using the Pd⁰ mediated coupling reaction of aryl di- and tri-bromides with aryl bis- and tris-boronic acids. The doping procedures produce polyradical polycations in which (in the limit of 100% doping) each spin is coextensive in its spatial distribution with three neighbouring spins. Magnetic susceptibility studies show the expected ferromagnetic spin-coupling. In this respect the best of these systems is the polymer obtained by the Pd⁰ mediated coupling of 1,3-dibromo-5-tetradecylbenzene with tris(4-boronic acid-2-hexyloxyphenyl)amine which was subsequently p-doped with NO⁺BF₄^– . A Brillouin function fit to the field dependence of the magnetization of this doped polymer at 2 K corresponds to an average spin S of 5/2. The best levels of doping achieved so far are about 15% of the theoretical maximum. These are sufficient to demonstrate the genuine high-spin nature of these polymers but are well short of the ca. 70% percolation limit needed for bulk superparamagnetic or ferromagnetic behaviour. The low doping levels are attributed to steric rather than coulombic effects.