Acta Crystallographica Section B

Structural Science

Volume 59, Part 6 (December 2003)

research papers

Acta Cryst. (2003). B59, 787-793 [ doi:10.1107/S0108768103022729 ]

Protonation site and hydrogen bonding in anhydrous and hydrated crystalline forms of doxazosin mesylate from powder data

V. V. Chernyshev, D. Machon, A. N. Fitch, S. A. Zaitsev, A. V. Yatsenko, A. N. Shmakov and H.-P. Weber

Abstract: The three-dimensional solid-state structures of two modifications of doxazosin mesylate C₂₃H₂₆N₅O₅⁺·CH₃SO₃^-, 4-amino-2-[4-[(2,3-dihydro-1,4-benzodioxin-2-yl)carbonyl]piperazin-1-yl]-6,7-dimethoxyquinazoline methanesulfonate, a commonly used antihypertensive agent, have been determined by synchrotron X-ray powder diffraction. An anhydrous form (A) and a dihydrate form (dG) crystallize in monoclinic space groups. In both forms the doxazosin molecule is protonated at the N1 atom of the quinazoline bicycle. The N1 atom, and the amino H atoms and O atoms of the mesylate moieties are involved in three-dimensional hydrogen-bonding networks, while solvent water molecules and carboxamide O atoms are also incorporated in a hydrogen-bonding network in dG.

Keywords: doxazosin mesylate; polymorphism; synchrotron powder diffraction; structure determination from powder data; grid search; Rietveld refinement.


	Rietveld powder data file (CIF format) (229.6 kbytes) Contains datablock SX5006_A

	Rietveld powder data file (CIF format) (330.5 kbytes) Contains datablock SX5006_dG

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