Crystal structure of minocycline hydrochloride dihydrate form A, C_(23)H_(28)N_3O_7Cl (H_2O)_2

摘要

The crystal structure of minocycline hydrochloride dihydrate has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Minocycline hydrochloride dihydrate crystallizes in space group P2(1)2(1)2(1) (#19) with a = 7.40772(1), b = 14.44924(3), c = 22.33329(4) angstrom, V = 2390.465(12) angstrom(3), and Z = 4. The minocycline cation is a zwitterion: both dimethylamino groups are protonated and one hydroxyl group is ionized. A potential ambiguity in the orientation of the amide group was resolved by considering Rietveld refinement residuals and displacement coefficients, as well as DFT energies. The crystal structure is dominated by hydrogen bonds. Both water molecules and a hydroxyl group act as donors to the chloride anion. Both protonated dimethyl amine groups act as donors to the ionized hydroxyl group. Several intramolecular O-H center dot center dot center dot O hydrogen groups help determine the conformation of the cation. The powder pattern is included in the Powder Diffraction File (TM) as entry 00-066-1606. (C) 2018 International Centre for Diffraction Data.