Single crystal x-ray structures of 2-pyridinecarboxaldehydeazine and biacetylazine: implications of the conjugation in systems with carbon-nitrogen double bonds
Date of Original Version
Crystal structures were determined for two compounds, 2-pyridinecarboxaldehydeazine, 1, and biacetylazine, 2. 2-Pyridinecarboxaldehydeazine crystallizes in space group P21/c with a = 10.0487(7) Å, b = 4.6452(7) Å, c = 11.6700(11) Å, β = 91.030(6)°, V = 544.65(10) Å3, Z = 2, R = 0.0345. Biacetylazine crystallizes in space group C2/c with a = 9.879(7) Å, b = 12.409(4) Å, c = 7.950(6) Å, β= 98.44(6)°, V = 964.0(11) Å3, Z = 4, R = 0.0496. Comparison of the imine bond lengths of these and other azine and diimine systems found in the literature suggests that conjugation of imines is better through the carbon-carbon bond than through the nitrogen-nitrogen bond. Semiempirical structural calculations demonstrate that the N-N bond in these azines is rotationally soft, thereby allowing significant twisting at little energy cost. This accounts for the observation that 1 is planar and 2 is not. © 1999 American Chemical Society.
Publication Title, e.g., Journal
Chemistry of Materials
Kesslen, Eric C., William B. Euler, and Bruce M. Foxman. "Single crystal x-ray structures of 2-pyridinecarboxaldehydeazine and biacetylazine: implications of the conjugation in systems with carbon-nitrogen double bonds." Chemistry of Materials 11, 2 (1999): 336-340. doi: 10.1021/cm9805673.