Theophylline , crystal structure

During their preparation, drug crystals may incorporate one or more solvent molecules to form solvates. The most common solvate is water. If water molecules are already present in a crystal structure, the tendency of the crystal to attract additional water to initiate the dissolution process is reduced, and solvated (hydrated) crystals tend to dissolve more slowly than anhydrous forms. Significant differences have been reported in the dissolution rate of hydrated and anhydrous forms of ampicillin, caffeine, theophylline, glutethimide, and mercaptopurine. The clinical significance of these differences has not been examined but is likely to be slight. 

N.m.r. spectra of xanthine, theobromine, theophylline, caffeine, and their conjugate acids have been analysed. The AT-ray crystal structure of (theobromine)2 H2I8 shows it to be a polyiodide salt with alternating cationic (H-bonded protonated theobromines) and anionic (Iti ions) layers. ... 

Cu(NN)(No3)2 (NN = bipy, phen, 2,9-dimethyl-l,10-phen, and 3,3 -dimethylene-4,4 -dimethyI-2,2 -biquinoline) have been prepared. Copper is approximately square pyramidal in bis(theophyllinatoXdiethylenetriamine)copper(ii) the terdentate di-ethylenetriamine and N-7 of the strongly bound theophyllinate (109) define the equatorial plane and a second theophyllinate is bonded to the axial position through N-7—thus the two purines occupy very different co-ordination sites. The crystal structure of [Cu(dpt)2]2 (dptH = 1,3-diphenyltriazine) shows discrete Cu2(dpt)4 units with a syn-syn structure as in Cu"-acetate,H20 (110). ... 

H. Wiedenfeld and F. Knoch, The crystal structure of the theophylline-urea complex, Archiv. Pharm. (Weinheim, Ger.), 319, 654-659 (1986). 

E. Shefter, Structural studies on complexes. IV. Crystal structure of a 1 1 5-chlorosalicylic acid and theophylline complex, J. Pharm. ScL, 58, 710-714 (1969). 

Figure 8.5 Pharmaceutical co-crystal components and a fragment of the solid-state co-crystal structure for (a) theobromine and malonic acid, (b) theophylline and D- and DL-malic acids and (c) AMG-517 and sorbic add. - ...

Case study theophylline anhydrate and monohydrate The type of structural information that can be obtained from the study of the x-ray diffraction of single crystals will be illustrated through an exposition of studies conducted on the anhydrate and hydrate phases of theophylline (3,7-dihydro-l,3-dimethyl-LH-purine-2,6-dione). The unit cell parameters defining the two phases are fisted in Table 7.2, while the structure of this compound and a suitable atomic numbering system is located in Fig. 7.3. 

Nakao, S. Fujii, S. Sakai, T. Tomita, K.-I. The crystal and molecular structure of the 2 1 molecular complex of theophylline with phenobarbital. Acta Crystallogr. 1977, B33, 1373-1378. 

In contrast to the emphasis placed on the crystal rather than the molecular structures of the compounds discussed above, the conformation of 1,3-bis-(8-theophylline)propane (18 n = 3) is of considerable importance. This compound was studied since, of the series of compounds theophylline and... 

Figure 8.19 Similar structural motifs between (a) a co-crystal hydrate of theophylline and citric acid, (b) citric acid monohydrate and (c) theophylline monohydrate. ...

Very little structural information is available for cadmium(II) complexes with neutral oxopurines. Nevertheless, the basicity of the N-donors in this kind of oxopurine ligand, as well as the softness, increases after the dissociation of at least one of the protons. Consequently, most of the available crystal data concerning complexes of such ligands refer to the tmivalent anions of hypoxanthine (Hhyp), xanthine (Hxan) or theophylline (Htheo). Neutral hypoxanthine yields the compound [Cd2(p2-N3,N9-H(N7)hyp)2(p2 H20)2(S04)2(H20)2] [27], in which the... 

---