Structure of 2,3-butanedione dihydrazone and IR study of higher polyazines: a new class of polymeric conductors

Polyazines, H/sub 2/N single bond (N double bond C(CH/sub 3/) single bond C(CH/sub 3/) double bond N)/sub x/ single bond NH/sub 2/, of various chain lengths have been prepared and studied by IR spectroscopy. An x-ray crystal structure was done on the monomer of this series, 2,3-butanedione dihydrazone (x = 1). It crystallized in space group P4/sub 2//n with cell constants a = 12.172 (3) A and c = 4.115 (1) A and Z = 4; intensity data were collected from 3.0/sup 0/ less than or equal to 2theta less than or equal to 65.0/sup 0/. The monomer is planar with long carbon nitrogen double bonds (1.291 (1) A) in the E conformation, the methyl groups are anti across the short carbon-carbon single bond (1.474 (2) A), and the lone pairs across the nitrogen-nitrogen single bonds are gauche. The anomalous bond lengths indicate a degree of ..pi..-bond conjugation in this molecule. The higher molecular weight materials are yellow to brown powders, are stable to air, have high melting points, and are surprisingly resistant to hydrolysis. Correlation of IR spectra of the monomer and sequentially increasing chain length polymers shows that the highest molecular weight material is at least 45 monomer units long and is planar with double bonds in the E conformation and all single bonds in the anti conformation. As in the monomer, the position of the C double bond N resonance indicates conjugation of the ..pi.. system along with polymer chain.