Structure and conformation of 2,3,4-triphenyl-1-oxa-4-azabutadiene

2,3,4-triphenyl-1-oxa-4-azabutadine (C20H15NO) has been studied by X-ray an alysis and AMI molecular orbital methods. It crystallises in the triclinic space group P-l with a = 9.414(3), b = 10.479(3), c = 8.385(2) Angstrom, al pha = 103.31(3)degrees beta = 97.10(3)degrees, gamma = 74.09(1)degrees, V = 772.5(4) Angstrom(3), Z = 2, D-c = 1.227 g cm(-3), and mu(MoK alpha) = 0.0 75 mm(-1) and F-000 = 300. The structure was solved by direct methods and r efined to R = 0.043 for 2672 reflections [I > 2 sigma(1)]. The conformation al analysis of the title compound were investigated by semi-empirical quant um mechanical AM1 calculations. The minimum conformation energies were calc ulated as a function of the three torsion angles theta(1)(O(1)C(7)C(8)N( 1) ), theta(2)(C(8)N(1)C(IS)C(16)) and theta(3)(C(14)C(9)C(8)N(1)). The result s are compared with the X-ray results. C=O and C=N groups are twisted about each other by 95.5(2)degrees. (C) 2000 Elsevier Science B.V. All rights re served.