The preparation, X-ray crystal structures, and thermal analyses of five solvates of the non-nucleoside reverse transcriptase inhibitor Nevirapine are reported. Thermogravimetric traces for the solvates indicated the following compositions (N ) nevirapine): N • (ethyl acetate) 0.5 (1), N • (dichloromethane) 0.5 (2), N • (toluene) 0.5 (3), N • (water) 0.5 (4), and N • (1,4-dioxane) 1.5 (5). Centrosymmetric, hydrogen-bonded nevirapine dimers occur in the crystals of 1-3 and in a previously characterized, unsolvated form of the drug 6. In crystals of 4, drug molecules are linked by a single N-H • • • OdC hydrogen bond only, whereas solvate 5 contains noncentrosymmetric nevirapine dimers. Solvent molecules in 1-3 occupy channels, whereas the water molecules in 4 occupy isolated sites and 1,4-dioxane molecules in 5 occupy layers. These inclusion modes are described with reference to the thermal behaviors of the solvates recorded in TGA and DSC.
X-ray structural and thermoanalytical data for a series of solvates 2-7 of the anti-HIV drug nevirapine containing primary alcohols CH 3 (CH 2 ) n OH with n = 2-7 are reported. The structures of 2-7 are based on a common isostructural framework comprising centrosymmetric hydrogen-bonded nevirapine dimers and contain a common channel parallel to the crystal b-axis whose repeat length spans a narrow range (*8.43-8.52 Å ) in the series and accommodates the various solvent molecules in 2-7. Thermogravimetry yielded a guest-host ratio close to 0.5 for the 1-butanol solvate 3 and a steady decrease in this ratio from 0.43 to 0.32 for the solvates 4-7. This anomalous stoichiometric variation was resolved following successful X-ray analysis of solvate 3 which revealed that the length spanned by the disordered 1-butanol molecule is commensurate with the channel periodicity b, resulting in a stoichiometric compound. Instead, solvates 5-7, for which single crystal X-ray data were available, showed significant disorder for the solvent molecules, attributed to their increasing chain lengths being incommensurate with the parameter b.
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