IR spectroscopy of pristine and iodine-doped permethylpolyazine

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Mid- and near-IR spectra for pristine and iodine-doped permethylpolyazine (-[N=C(CH3)-C(CH3)=N]x-) are reported for both natural isotopic abundance and 100% 15N-enriched samples. For the undoped samples the degree of conjugation along the polymer backbone is fairly small. Upon exposure to iodine, the only changes in the IR spectra are found in the near IR where a very intense band grows in above 4000 cm-1 and in the mid-IR where there is development of a weaker, poorly resolved doublet around 1500 cm-1. The strong absorption in the near-IR has none of the characteristics normally associated with gap states and so is assigned to be the tail of the visible, electronic absorption of triiodide. The doping-induced feature in the mid-IR is a doublet; the higher energy band is diminished upon 15N enrichment, while the lower energy peak is unaffected by the isotopic substitution. Complexation of I+ to the polymer, probably through the imine π bond, is thought to be responsible for the new mid-IR peaks. There is no evidence that the polymer has been oxidized.

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Chemistry of Materials