The structures of the pyrimidines and purines. VI. The crystal structure of theophylline

Abstract

Theophylline crystallizes in the monoclinic space group P21, nearly P2z/a, with unit-cell dimensions a = 13.3, b ----15.3, c = 4.50/~, fl ----99.5 °. The x and y coordinates were determined by an application of the isomorphous-replacement method and the z coordinates by a consideration of the hydrogen bond system possible in the crystal; these coordinates were refined by difference syntheses and difference generalized projections. The standard deviation in a bond length is 0.01 /~. The intramolecular distances are similar to those in other compounds containing a purine or pyrimidine group, but bond lengths of substituents attached to the purine ring are equivalent to the sum of the single-or double-bond radii.

1:1 Molecular Complex of Theophylline and p-Nitroaniline

“…1 shows the molecular structure of the title complex, the 1:1 molecular complex of theophylline and p-nitroaniline, (I). The fused theophylline rings are essentially planar and the bond lengths and angles within the molecule are in fairly good agreement with those observed in theophylline monohydrate (Sutor, 1958) and other theophylline complexes, e.g. 1:1 theophylline-sulfathiazole (Shefter & Sackman, 1971).…”

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

“…0.1 g) were submitted to different temperatures (35,40,47, and 608C) during defined time periods, and sealed in glass capillary tubes in order to record their FT-Raman spectra.…”

“…The crystal structures of both TPa and TPh have been published, [39][40][41] being evident that the major structural differences between the two polymorphs occur in the hydrogen-bonding network. These structural differences have a direct effect on the vibrational spectra (both in the position and in the relative intensities of the bands) as was reported previously by some of us.…”

X-ray and Neutron Diffraction in the Study of Organic Crystalline Hydrates

“…Since this process is accompanied by pseudomorphosis, i.e., the destruction of the mother crystal into a multi-crystalline powder of the same shape, indicated by the clear single crystal turning opaque, the loss of water is connected with a major change in structure as is characteristic for stoichiometric hydrates. Caffeine 0.8 hydrate [35][36][37] and theophylline monohydrate [38,39] form channels in their structure as well. Both materials are isostructural and stoichiometric, while the water release behaviour from the channels differs significantly [40][41][42].…”