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β-Polymorph of phenazepam: a powder study.

Gleb B Sergeev¹, Boris M Sergeev, Yurii N Morosov

¹Department of Chemistry, Moscow State University, 119991 Moscow, Russian Federation.

Acta Crystallographica. Section E, Structure Reports Online

|May 19, 2011

Summary

The beta-polymorph of phenazepam was created using cryomodification. This new crystal form exhibits distinct dihedral angles and intermolecular bonding compared to the alpha-polymorph.

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Area of Science:

Crystallography
Solid-state chemistry
Pharmaceutical science

Background:

Phenazepam is a known benzodiazepine with an established alpha-polymorph.
Polymorphism in pharmaceuticals can significantly impact drug properties and efficacy.
Understanding different crystal forms is crucial for drug development and manufacturing.

Purpose of the Study:

To obtain and characterize a novel beta-polymorph of phenazepam.
To investigate the structural differences between the alpha and beta polymorphs of phenazepam.
To explore the effects of cryomodification on crystal structure.

Main Methods:

Cryomodification of the known alpha-polymorph of phenazepam.
Single-crystal X-ray diffraction analysis to determine molecular and crystal structures.
Analysis of dihedral angles and intermolecular interactions (hydrogen bonding).

Main Results:

The beta-polymorph of phenazepam (C15H10BrClN2O) was successfully synthesized via cryomodification.
Molecules in both polymorphs form centrosymmetric dimers through N-H⋯O hydrogen bonds.
The beta-polymorph exhibits a larger dihedral angle (86.2°) between aromatic rings compared to the alpha-polymorph (75.4°).
Weak intermolecular C-H⋯O hydrogen bonds in the beta-polymorph create layered structures parallel to the bc plane.

Conclusions:

Cryomodification is an effective method for obtaining new polymorphic forms of phenazepam.
The beta-polymorph of phenazepam possesses distinct structural characteristics, particularly in its dihedral angles and intermolecular interactions.
The identified structural differences may influence the physicochemical properties of phenazepam, warranting further investigation.