A monoclinic polymorph of theophylline

Abstract

A monoclinic polymorph of theophylline, C7H8N 4O2, has been obtained from a chloro-form/methanol mixture by evaporation under ambient conditions. The new polymorph crystallizes with two molecules in the asymmetric unit. The structure features intermolecular N-H⋯O hydrogen bonds, resulting in the formation of dimers between two crystallographically different molecules; each molecule acts as both donor and acceptor.