Direct Evidence of a Bipolaron Charge Carrier in Conducting Polyazines by 13C and 15N Solid State NMR: Detection of a Nitrenium Cation by Natural Abundance 15N Solid State NMR
Benjamin Chaloner-Gill, William B. Euler, Paul D. Mumbauer, James E. Roberts, Journal of the American Chemical Society, 1991, 113, 6831 – 6834
Abstract
Natural abundance 13C and 15N solid-state NMR experiments were performed on undoped and doped samples of polyazine, (–N=C(R)–C(R)=N–)x. The topology of the polymer requires that doping-induced charge carriers must be either polaron (radical cations) or bipolarons (dications). Magnetic susceptibility measurements show that the iodine-doped polymers are diamagnetic, so the charge carriers must be bipolarons. The specific bipolaron charge carrier in polyazines has been identified: the nitrogens bear the charge primarily in the form of nitrenium cation. This is the first report of a nitrenium cation detected by 15N solid-state NMR spectroscopy. Independent of the subsitution of the polyazines, R = H or CH3, the same charge carrier is present.