X-ray Structure of N-(4-Nitrophenacyl)-4,5-diazafluoren-9-onium Bromide

The X-ray structure of the salt N-(4-nitrophenacyl)-4,5-diazafluoren-9-onium bromide 1, in the form of an acetic acid solvate, is reported. The compound crystallizes in the space group P1 with a = 6.2483(1)A, b = 11.8182(2)A, c = 14.8931(3)A, α = 67.543(1)°, β = 86.754(1)°, γ = 79.304(1)° and Z = 2. The quaternization of a nitrogen atom of the 4,5-diazafluoren-9-one molecule, manifested in the title cation, introduces significant asymmetry, reflected in differences in the geometries of the two pyridyl moieties. In constrast to related, previously reported tetracyclic systems that display a high degree of helical distortion, steric congestion in the title cation is minimal, rendering the 4,5-diazafluoren-9-onium moiety virtually planar. This is consistent with predictions based on NMR spectroscopy.