SOLID STATE CHARACTERIZATION OF METOPROLOL FREE BASE AND METOPROLOL TARTRATE.
CORINA IONESCU1, MINO R CAIRA2, MARIUS T BOJITA1, LUIGI R NASSIMBENI2, WELCOME T MHLONGO2
1Faculty of Pharmacy, UMF "Iuliu Hatieganu", 13 Emil Isac,
Cluj-Napoca, Romania
2Department of Chemistry, University of Cape Town, South Africa

Abstract:

Structural and thermal properties of racemic metoprolol free base and metoprolol tartrate have been investigated by single crystal and powder X-ray diffraction, hot stage microscopy and differential scanning calorimetry. Only one polymorphic form of each compound was detected in batches prepared by recrystallization from various solvent systems. The free base (m.p. range 51-54ºC) crystallizes in the space group P2₁/n with four molecules in the unit cell. Metoprolol tartrate (m.p. range 121-125ºC) crystallizes in P2₁ with two formula units in the asymmetric unit, each of the former comprising two molecules of racemic protonated base and a dextro-tartaric acid anion. Hydrogen bonding stabilizes both crystal structures but is more extensive in the tartrate salt. Idealised powder X-ray diffraction patterns are reported for both compounds.

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