The Structure of Glyoxal Dihydrazone and Synthesis, Characterization, and Iodine Doping of Unsubstituted Polyazine
Benjamin Chaloner-Gill, Clair J. Cheer, James E. Roberts, William B. Euler, Macromolecules, 1990, 23, 4597 – 4603
Abstract
The unsubstituted polyazine, –[N=CH–CH=N]x–, has been synthesized from glyoxal dihydrazone and glyoxal. An X-ray crystal structure was done on the monomer glyoxal dihydrazone; it crystallized in space group P21/a with cell constants a = 7.744 (4) Å, b = 4.113 (1) Å, and β = 115.66 (3)° and Z = 2; intensity data were collected in the range 3.5 ≤ 2θ ≤ 60°. Refinement to convergence of the 683 independent reflections, I > 3σ(I), resulted in final anisotropic R = 0.056 and Rw = 0.059. The monomer is planar with a carbon-nitrogen double bond (1.278 Å) in the E conformation and a short carbon-carbon single bond (1.433 Å) in the anti conformation, similar to the methyl-substituted analogue, 2,3-butanedione dihydrazone. The polymer also appears to adopt the anti-E conformation and so is directly comparable to trans-polyacetylene. Both IR and solid-state NMR analyses show the presence of hydroxy-bearing defect sites; the azines are formed by an addition-elimination condensation, and the defects arise from sites where addition occurs but the subsequent elimination does not. Polyazine can be doped with iodine to give powders with room-temperature, pressed-pellet conductivities only as high as 1 × 10–6 Ω–1cm–1 because of the sp3 defects found along the polymer chain. The IR spectra of the doped materials indicate that the charge carrier is a bipolaron having a nitrogen-nitrogen or carbon-carbon double bond.