E. Maccaroni, E. Alberti, L. Malpezzi
Jan 7, 2009
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Journal
Crystal Growth & Design
Abstract
Azelastine, a widely commercialized drug for the treatment of allergic asthma and rhinitis, has been commonly used as anhydrous hydrochloride salt, but it was found to form also hydrates or solvates upon recrystallization. The anhydrous form can be isolated also by precipitation from CH3CN solution or quantitatively generated from the hydrated form by heating it near 180 °C. The crystal structures of the anhydrous and of the three different solvated species have been determined by unconventional ab initio powder diffraction methods using laboratory data only, supported by solid state 13C NMR spectra and thermal analyses. Crystals of the anhydrous form are monoclinic, P21/n, a = 13.7858(9) A, b = 16.3911(9) A, c = 9.4085(5) A, β = 97.540(4)°, V = 2107.6(2) A3, Z = 4; the hydrated form crystallizes in the triclinic P1 space group, a = 9.5594(8) A, b = 9.8208(8) A, c = 14.644(1) A, α = 86.726(5)°, β = 109.511(5)°, γ = 119.176(5)°, V = 1122.1(2) A3, Z = 2. The stability of the two systems, in comparison with...