Electronic structure and conformational properties of azines. Part 2. 2,5-Diacetyl-3,4-diazahexa-2,4-diene, a 2,3-diaza-1,3-diene with a synclinal conformation: an X-ray crystallographic, HeI photoelectron spectroscopic, and MNDO study

Abstract

2,5-Diacetyl-3,4-diazahexa-2,4-diene consists of two essentially planar halves that are twisted about each other by 102.7°. Bond lengths and orbital energies indicate strong conjugation between the electron lone-pair of one nitrogen atom and the double bonds of the other half of the molecule. The molecular structure and torsion around the N–N and C–C bonds have been studied by MNDO calculations. While the structure parameters are in reasonable agreement with experimental values, conformational properties are not treated adequately. According to these calculations orbital energies are nearly invariant to conformational changes.