Huang Z, Suzuki H, Ito M, Noguchi S. Characterization of Ambroxol and Its Hydrochloride Salt Crystals by Bromine K-Edge X-Ray Absorption Near-Edge Structure Spectroscopy and X-Ray Crystal Structure Analysis.
Chem Pharm Bull (Tokyo) 2023;
71:741-746. [PMID:
37661380 DOI:
10.1248/cpb.c23-00392]
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Abstract
Polymorphic crystals of ambroxol, forms I and II, and form A ambroxol hydrochloride crystals were characterized with bromine K-edge X-ray absorption near-edge structure (XANES) spectroscopy and single-crystal X-ray structure analysis. The XANES spectra had unique shapes depending on the crystal forms. Refined single-crystal structures revealed different interatomic interactions around bromine atoms, such as C-H…Br and N-H…Br hydrogen bonds, Br…O halogen bonds, and N-H…π interactions. Differences in these weak interactions could affect the electronic states of the bromines, resulting in differences in the XANES spectra. The results demonstrated that weak non-conventional interatomic interactions could alter the shape of XANES spectra. Hence, the spectra could be used for evaluating polymorphs of active pharmaceutical ingredients.
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