Crystallographic Studies of Eletriptan Hydrobromide: α-Form, β-Form and its Physicochemical Characterisation

Abstract

The single crystals of eletriptan hydrobromide for two polymorphs α and β were developed to study their structural properties. The forms crystallized in monoclinic system with noncentrosymmetric space group. The molecular structure confirms eletriptan to exist as a hydrobromide salt in 1:1 ratio. In α-form, the indole nitrogen participates in intermolecular hydrogen bonding with O=S=O, the bromine anion forms a bond only with nitrogen of pyrrolidine moiety. Whereas in β-form, the bromine anion forms a bond with the nitrogen of pyrrolidine and also to indole nitrogen (N₂–H–Br … N₁–H). The two α and β polymorphs exhibit conformational polymorphism. The polymorphs of eletriptan hydrobromide also showed different solid state characteristic properties confirmed by using different solid state techniques such as the powder X-ray diffraction, Single crystal analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), FTIR, and microscopy as well as variable humidity and temperature powder X-ray diffraction (VTPXRD).

Keywords:

• Eletriptan hydrobromide
• Conformational polymorphs
• crystal structures
• physico-chemical characterization

Acknowledgments

The authors wish to thank the management of Mylan Laboratories Limited for providing an opportunity to publish this work. We are also thankful to Dr. G. R. Desiraju (Department of Solid state and Structural Chemistry, Indian Institute of Sciences (IISC) (Bengaluru, India)) and Dr. K. Ravikumar and Dr. B. Sridhar (Laboratory of X-Ray Crystallography, Indian Institute of Chemical Technology (IICT) (Hyderabad, India)) for providing support on single crystal analysis.