Four salt phases of theophylline

Buist, Amanda and Kennedy, Alan and Manzie, Craig (2014) Four salt phases of theophylline. Acta Crystallographica Section C: Crystal Structure Communications, 70 (2). pp. 220-224. ISSN 0108-2701

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Abstract

The structures of two anhydrous salt phases of theophylline, namely 1,3-dimethyl-2,6-dioxo-7H-purin-9-ium tetra­fluoro­borate, C7H9N4O2+·BF4-, and 1,3-dimethyl-2,6-dioxo-7H-purin-9-ium chloride, C7H9N4O2+·Cl-, are reported together with the structures of two monohydrate salt forms, namely 1,3-dimethyl-2,6-dioxo-7H-purin-9-ium chloride monohydrate, C7H9N4O2+·Cl-·H2O, and 1,3-dimethyl-2,6-dioxo-7H-purin-9-ium bromide monohydrate, C7H9N4O2+·Br-·H2O. The monohydrate structures are mutually isostructural, with the cations and anions lying on crystallographic mirror planes (Z' = 1\over 2). The main inter­molecular inter­action motif is a hydrogen-bonding network in the same mirror plane. The tetra­fluoro­borate structure is based on planar hydrogen-bonded theopylline cation dimers; the anions inter­act with the dimers in a pendant fashion. The anhydrous chloride structure has Z' = 2 and in contrast to the other species it does not form planar hydrogen-bonded constructs, instead one-dimensional chains of cations and anions propagate parallel to the crystallographic c direction. An earlier report claiming to describe an anhydrous structure of theophylline hydro­chloride is re-examined in light of these results. It is concluded that the earlier structure has been reported in the wrong space group and that it has been chemically misidentified.

ORCID iDs

Buist, Amanda, Kennedy, Alan ORCID logoORCID: https://orcid.org/0000-0003-3652-6015 and Manzie, Craig;