High-Spin Cation Radicals of Meta-Para Aniline Oligomers

A series of linear and branched high-spin diand tri(cation radical)s (12•2+, 72•2+, 33•3+, 43•3+, and 93•3+) has been prepared by oxidation of the corresponding meta-para aniline oligomers. The oligo(cation radical)s are stable under ambient conditions. The formation and properties of the cation radicals has been studied in detail by cyclic voltammetry and UV-vis-near IR spectroscopy. ESR spectroscopy has provided the zero-field splittings, which are consistent with the topology of the molecules and the localization of the unpaired electrons. Variable temperature ESR measurements reveal that the signal intensity follows Curie’s law, consistent with a low-energy high-spin state. The stability of the high-spin meta-para aniline oligomers and the possibility to extend these systems demonstrate that alternating meta and para aniline oligomers are promising building blocks for future polaronic ferromagnets.