The structure–property relationship of four crystal forms of rifaximin

The crystal structures of four crystal forms of rifaximin, named α, β, δ and ε, have been elucidated by a combination of single crystal and powder diffraction experiments with synchrotron and X-ray sources. The crystal structures of the δ and ε forms have been determined from powder diffraction data alone. Hot stage microscopy has also been of paramount importance in the understanding of the β → α conversion process.