Pamoic acid determined from powder diffraction data

Abstract

The title compound [systematic name: 4,4′-methylenebis(3-hydroxy-2- naphthoic acid)], C23H16O6, has one half-molecule in the asymmetric unit. The molecular twofold rotational axis about the central C atom is preserved on crystallization. A chain formed by R22(8) hydrogen bonds runs along the c axis and an intramolecular O-H⋯O=C-OH hydrogen bond is also formed. The crystal structure was solved by simulated annealing from laboratory X-ray powder diffraction data, with data collected at room temperature. Rietveld refinement of this model led to a final Rwp value of 0.0391 at 1.39 Å resolution. © 2006 International Union of Crystallography All rights reserved.