The solid state forms of the sex hormone 17-β-estradiol

Abstract

The crystal structure of the single component form of the primary female sex hormone, 17-β-estradiol (BES), is reported, solved from single crystals obtained by sublimation. The Z′ = 2 P2₁2₁2₁ structure was computationally predicted as one of the thermodynamically plausible structures. It appears that the dehydration process for the very stable hemihydrate structure is a complex process, strongly affected by particle size and conditions. An experimental polymorph screen has produced six solid forms of BES, including novel acetonitrile and highly labile ethylene dichloride solvates, and reproduced previously reported methanol and propanol solvates. These have been characterized, as far as possible given the metastability relative to the hemihydrate (BES·0.5H₂O), by single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), hot-stage microscopy and Fourier transform infrared spectroscopy (FT-IR), sorting out some of the confusion in the earlier literature.