The crystal structure of givinostat hydrochloride monohydrate Form I has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Givinostat hydrochloride monohydrate Form I crystallizes in the space group P21 (#4) with a = 7.98657(17), b = 8.20633(10), c = 18.2406(6) Å, β = 98.1069(13)°, V = 1,183.55(4) Å3, and Z = 2 at 298 K. The crystal structure consists of layers of cations and anions/water molecules parallel to the ab-plane. The cations stack along the a-axis, with the phenyl and naphthalene rings alternating in the stacks. Hydrogen bonds link the cations, anions, and water molecules in two-dimensional networks parallel to the ab-plane. The powder pattern has been submitted to the International Centre for Diffraction Data for inclusion in the Powder Diffraction File™ (PDF®).
