Combination of energy minimizations and rigid-body Rietveld refinement: the structure of 2,5-dihydroxybenzo[de]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one

The crystal structure of the yellow pigment 2,5-dihydroxybenzo[de]benzo[4,5]imidazo[2,1-a]isoquinol­in-7-one (C₁₈H₁₀N₂O₃) was determined from powder data. The crystal structure was solved by minimizing the intermolecular energy starting from random packings. Subsequently, the structure was refined by rigid-body Rietveld analysis, using synchrotron powder data. The refinement included several intramolecular degrees of freedom. The compound crystallizes in Pna2₁, Z4, with lattice parameters a13.2759 (3), b20.9561 (5), c4.7798 (1) Å, and V1329.79 (5) ų. The crystal consists of planar molecules, connected by hydrogen bonds of the types O–H...OH and O–H...N, which form a three-dimensional hydrogen-bond network.