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10:37
Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Formation of isomorphic desolvates: creating a molecular vacuum
G A Stephenson1, E G Groleau, R L Kleemann
1Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, Indiana 46285, USA. Stephenson_GregoryA@lilly.com
Journal of Pharmaceutical Sciences
|May 20, 1998
Summary
This study explores isomorphic desolvates, crystalline structures that lose solvent but maintain order. Investigating their solid-state properties reveals insights into energy states and structural relaxation mechanisms.
Area of Science:
- Solid-state chemistry
- Crystallography
- Materials science
Background:
- Isomorphic desolvates are crystalline organic substances that lose solvent molecules from their lattice while retaining three-dimensional structural order.
- This process results in a high-energy metastable lattice state compared to the original solvate.
Purpose of the Study:
- To investigate the poorly understood phenomenon of isomorphic desolvates.
- To examine the solid-state properties, hygroscopicity, and structural relaxation of specific pharmaceutical hydrates (cephalexin, cefaclor, erythromycin A, spirapril hydrochloride).
Main Methods:
- Hygroscopicity was evaluated using a vacuum moisture balance.
- Structural relaxation was measured using X-ray powder diffraction (XRPD) and isothermal microcalorimetry.
- Analysis was guided by Kitaigorodski's close packing principle.
Main Results:
- The study characterized the high-energy state of desolvated lattices.
- Investigated the mechanisms for reducing internal energy: solvent resorption or structural relaxation.
- Observed that relaxation processes increase packing efficiency by reducing unit cell volume.
Conclusions:
- Isomorphic desolvates represent a significant class of crystalline materials with unique energy profiles.
- Structural relaxation is a key process for desolvated lattices to achieve lower energy states.
- Understanding these properties is crucial for controlling solid-state behavior in pharmaceuticals.
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