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Four salt phases of theophylline
Author(s) -
Buist Amanda R.,
Kennedy Alan R.,
Manzie Craig
Publication year - 2014
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229614000825
Subject(s) - tetrafluoroborate , isostructural , chemistry , crystallography , hydrogen bond , anhydrous , bromide , crystal structure , salt (chemistry) , protonation , chloride , molecule , ion , stereochemistry , inorganic chemistry , ionic liquid , organic chemistry , catalysis
The structures of two anhydrous salt phases of theophylline, namely 1,3‐dimethyl‐2,6‐dioxo‐7 H ‐purin‐9‐ium tetrafluoroborate, C 7 H 9 N 4 O 2 + ·BF 4 − , and 1,3‐dimethyl‐2,6‐dioxo‐7 H ‐purin‐9‐ium chloride, C 7 H 9 N 4 O 2 + ·Cl − , are reported together with the structures of two monohydrate salt forms, namely 1,3‐dimethyl‐2,6‐dioxo‐7 H ‐purin‐9‐ium chloride monohydrate, C 7 H 9 N 4 O 2 + ·Cl − ·H 2 O, and 1,3‐dimethyl‐2,6‐dioxo‐7 H ‐purin‐9‐ium bromide monohydrate, C 7 H 9 N 4 O 2 + ·Br − ·H 2 O. The monohydrate structures are mutually isostructural, with the cations and anions lying on crystallographic mirror planes ( Z ′ = ). 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.