Abstract
The X-ray structure of diethyl 10-(4-nitrobenzoyl)-pyrrolo[1,2-a][4,5]diazafluoren-5-one-8,9-dicarboxylate, a representative compound that features a tetracyclic ring system, is reported. It crystallizes in the monoclinic space group P21/c with unit cell parameters a = 7.9340(2)Å, b = 31.0480(7)Å, c = 9.4411(2)Å, β = 94.956(1)°, and Z = 4. Significant helical distortion of the tetracyclic system was observed, with an extent comparable to that occurring in pyrrolophenanthroline ring systems previously investigated. The distortion is induced by an intramolecular steric repulsion between the pyridine nitrogen atom and the carbonyl carbon atom of the nitrobenzoyl moiety.
