Crystal and molecular structure of α,α′-azobis[4-bromobenzaldehyde]bis (O-carboxyoxime)diethyl ester

Abstract

The title compound is a dimer of chemical formula (C₁₀H₉BrN₂O₃)₂ and yielded crystals of two forms, one monoclinic with space groupP2₁/a and the other triclinicP¯1. Diffraction data from both forms were collected and used in solving the structure by the heavy-atom method. The coordinates were refined by block-diagonal least-squares procedures to anR index of 0.07 for the 2334 reflections of the triclinic crystal and 0.115 for the 2306 reflections of the monoclinic crystal. The results have led to the assignment of the structure (I) for the title compound. In both crystals, the molecule is planar, except for the nitrogen atoms linking the two halves of the dimers. The plane through the four atoms (C−N=N−C) bridging the two halves is nearly perpendicular to the molecular plane in both cases. The molecules in the two crystals show very similar bond lengths and bond angles, but the molecular packing is quite different (Go, Kartha & Lu, 1974). The triclinic form, in addition, showed that the central nitrogen atom is disordered, occupying the two positions above and below the molecular plane with equal probability.